1. science
2. ecology
3. waste management
4. recycling

INTEGRATED MUNICIPAL SOLID WASTE
MANAGEMENT MANUAL
In Latin American
and Caribbean Cities
INTEGRATED MUNICIPAL SOLID WASTE MANAGEMENT MANUAL
IN LATIN AMERICAN AND CARIBBEAN CITIES
(Based on the original edition: Manual Gerenciamento Integrado de Resíduos Sólidos, 2001)
1st EDITION – 2008
MINISTRY FOR THE ENVIRONMENT
AND TERRITORY – ITALY
BRAZILIAN INSTITUTE OF MUNICIPAL
ADMINISTRATION – IBAM
General Director
Corrado Clini
General Director
Mara Biasi Ferrari Pinto
Director, Division I, Environment
and Development Research Department
Paolo Soprano
Director, National School of Urban
Services – ENSUR
Tereza Cristina Baratta
Consultant, Division I, Environment
and Development Research Department
Pierluigi Manzione
Director, Urban Development and the Environment
– DUMA
Ana Lucia Nadalutti La Rovere
INTERNATIONAL DEVELOPMENT
RESEARCH CENTRE, IDRC – Canada
PUBLICATION
Technical coordination
Karin Segala
Senior Program Specialist
Walter Ubal Giordano
Research Officer
Alicia Iglesias
Program Assistant
Clara Saavedra
Webmaster
María Noel Estrada
Technical content – Update and Adaptation
Gilson Leite Mansur
José Henrique Penido Monteiro
Chapter 2 – Collaboration
Victor Zular Zveibil
Silvia Martarello Astolpho
Technical Revision
Andrea Pitanguy de Romani
Karin Segala
Translation from Spanish to English
Liliana Battipede and David Reed
Design and Layout
Roberto Tostes / Doble Clic Editoras
Publishing Coordination and Revision,
English version
Víctor L. Bacchetta and Laura Pallares
Manual on municipal solid waste integrated management in Latin American and Caribbean cities /
José Henrique Penido Monteiro …[et al]; updated and adapted by Gilson Leite Mansur and José
Henrique Penido Monteiro; technical coordination by Karin Segala; translation by Liliana
Battipede and David Reed. – Montevideo: IDRC, 2008.
264p.; 21 X 29.7cm
Adapted from: Manual gerenciamento integrado de resíduos sólidos, 2001.
1. Solid waste. I. Monteiro, José Henrique Penido. II. Mansur, Gilson Leite. III. Segala, Karin
(coord.). IV. International Development Research Centre (IDRC).
INDEX
PRESENTATION
6
PREFACE
1
12
The general situation of solid waste management
in Latin America and the Caribbean
1.1
Introduction
1.2
Regional Evaluation of Municipal Solid Waste Management
Services in Latin America and the Caribbean
1.3
Solid waste sector trends
14
15
15
22
2
Integrated Solid Waste Management
28
3
Institutional models and payment for services
3.1
Concept
3.2
Forms of administration
3.3
Payment for services
3.3.1
Guidelines for the calculation of a waste collection rate
32
33
34
39
42
4
Legislation
4.1
4.2
4.3
4.4
and Environmental Licenses
Introduction
Legislation
Environmental Licenses
Regulations applicable to solid waste
44
45
45
47
48
5
Solid waste: origin, definition and characteristics
5.1
Definition of rubbish and solid waste
5.2
Solid waste classification
5.2.1
Potential environmental contamination risks
5.2.2
Nature and origin
5.3
Characteristics of solid waste
5.3.1
Physical characteristics
5.3.2
Chemical characteristics
5.3.3
Biological characteristics
5.4
Influence of solid waste characteristics on urban
cleaning system planning
5.5
Factors that influence solid waste characteristics
5.6
Processes for determining principal physical
characteristics
50
51
51
51
52
59
59
62
63
6
Solid waste quantity projections
70
7
Solid waste preparation and storage
7.1
Concept
7.2
The importance of appropriate preparation and storage
7.3
Characteristics of pre-collection storage containers
7.4
Domestic waste pre-collection preparation and storage
7.5
Pre-collection storage of street waste
7.6
Pre-collection storage of waste in low
demographic density and low-income areas
7.7
Pre-collection storage of waste produced by large
generators
7.8
Special domestic waste pre-collection storage
7.9
Special origin waste pre-collection storage
74
75
75
76
78
80
63
65
66
82
83
84
87
8
Solid waste collection and transport
8.1
Domestic waste collection and transport
8.1.1
Concept
8.1.2
Collection regularity
8.1.3
Collection frequency
8.1.4
Collection times
8.1.5
Restructuring domestic collection routes
8.1.6
Collection vehicles
8.1.7
Tools and implements used by collectors
8.2
Public solid waste collection and transport
8.2.1
Concept
8.2.2
Collection of waste gathered by sweeping
8.2.3
Collection of waste from weeding and vegetation cutting
8.2.4
Tree pruning waste collection
8.2.5
Collection of rubble and other construction waste
8.2.6
Special collections
8.2.7
Vehicles and equipment used for collection
8.3
Waste collection in tourist cities
8.4
Solid waste collection in informal settlements
8.5
Collection of medical waste
8.5.1
Acknowledgement of the problem
8.5.2
Segregation
8.5.3
Separate collection of common, infectious
and special waste
8.5.4
Vehicles for collection and transport
8.5.5
Aspects of collection planning
90
91
91
91
92
93
94
100
105
106
106
106
107
108
109
109
110
113
114
115
115
116
9
Solid waste transfer
9.1
Concept
9.2
Types of transfer station
9.2.1
Direct transfer station
9.2.2
Station with storage facilities
9.2.3
Alternative transfer systems
9.3
Vehicles and machines for transfer stations
120
121
122
122
122
124
124
10
Street cleaning
10.1
The importance of street cleanliness
10.2
Waste found in the street
10.3
Street cleaning services
10.3.1
Sweeping services
10.3.2
Weeding and scraping services
10.3.3
Cutting services
10.3.4
Drain cleaning services
10.3.5
Market cleaning services
10.3.6
Manual and mechanical waste removal services
10.3.7
Beach cleaning services
10.4
How to reduce street waste
10.5
Street cleaning in tourist cities
126
127
128
129
130
136
138
143
145
146
147
150
152
11
Recovery of recyclable materials
11.1
Concept
11.2
Selective collection programs
11.2.1
Selective door to door collection
11.2.2
Voluntary Drop-off Centres (VDC)
11.2.3
Segregator organizations
154
155
156
157
159
161
117
117
119
12
Solid waste treatment
12.1
Concept
12.2
Domestic solid waste treatment
12.2.1
Recycling
12.2.2
Composting
12.2.3
Choosing a treatment option
12.3
Treatment of special domestic waste
12.3.1
Construction rubble
12.3.2
Tyres
12.3.3
Batteries and fluorescent tubes
12.4
Treatment of waste from special sources
12.4.1
Industrial solid waste
12.4.2
Radioactive waste
12.4.3
Port and airport waste
12.4.4
Medical waste
164
165
166
166
170
174
177
177
182
184
184
184
185
186
186
13
Solid waste final disposal
13.1
Introduction
13.2
Impacts of inappropriate solid waste disposal
13.3
Sanitary landfill
13.3.1
Sanitary landfill site selection
13.3.2
Environmental licenses
13.3.3
Master plan
13.3.4
Landfill installation
13.3.5
Sanitary landfill operation
13.3.6
Equipment
13.4
Controlled landfills
13.5
Environmental recuperation of refuse dumps
13.6
The situation of segregators
13.7
Special domestic waste disposal
13.7.1
Construction rubble disposal
13.7.2
Disposal of batteries
13.7.3
Disposal of fluorescent tubes
13.7.4
Disposal of tyres
13.8
Disposal of waste from special sources
13.8.1
Industrial waste disposal
13.8.2
Radioactive waste disposal
13.8.3
Port and airport waste disposal
13.8.4
Medical waste disposal
13.9
Sanitary landfills and carbon credits:
Opportunities to help resolve
environmental problems
13.9.1
Greenhouse effect: causes and consequences
13.9.2
The “logic” of carbon credits
13.9.3
Circumstances in which biogas from a sanitary
landfill can be utilized
13.9.4
Requirements for the implementation of GHG
emission reduction projects in solid waste landfills
13.9.5
General considerations
196
197
198
199
203
211
213
215
222
232
233
236
238
239
239
240
240
241
241
241
245
246
246
247
248
249
251
252
253
BIBLIOGRAPHY
255
GLOSSARY OF ACRONYMS
258
GLOSSARY
259
PRESENTATION
The role of local authorities for
a better environmental policy
The training course on integrated urban solid waste management in municipalities of
Latin America and the Caribbean, held in December 2005 in Rio de Janeiro (Brazil),
represented a significant step in the fruitful collaboration between the Ministry for the
Environment and Territory of Italy and the International Development Research Centre
of Canada (IDRC) through the Environmental Management Secretariat (EMS). This
collaboration had previously resulted in significant benefits through the organization
of a high level meeting held in Sao Paulo (Brazil), which gathered experts, administrators,
professionals and heads of public institutions in order to quantify the process towards
sustainability in the urban solid waste management sector and to assess the situation
through an exchange of information and an evaluation of best practices in each field.
These peak activities, together with some others carried out during the year, pertain
to the Memorandum of Understanding (MoU) signed by the Ministry for Environment
and Territory of Italy and IDRC, which came into force in 2005 and is aimed at achieving
common objectives related to environmental protection and integrating them with social
and economic development. This agreement focuses attention on some specific areas
related to local environmental policy, such as sustainable water and sanitation
management, urban waste management, the promotion of clean technologies and
industrial processes and the use of renewable energy sources, all of which are
processes geared to ensuring local sustainable development.
The MoU established a partnership between the two institutions and implies not only
that both parties are committed to achieving the agreed objectives, but also their
intention to initiate actions at all levels with the participation of developed and
developing countries, international institutions, NGOs and the private sector. The
resulting projects (specifically in Latin America and the Caribbean) will be expressly
devoted to establishing new partnerships (within the broad category of the “type II
initiatives” launched in Johannesburg) in areas of interest common to private and public
sectors, or within each of them, and to supporting local authorities in developing
voluntary processes at the local level.
In this regard, the role that municipalities can play in the sustainability process is of
great importance: the local dimension should be considered as the most significant
for experimenting with new environmental strategies and best practices and demonstrating their effectiveness on a broader dimension. As stated in chapter 28 of Agenda
21, local authorities construct, operate and maintain economic, social and environmental infrastructure; oversee planning processes; establish local environmental
policies and regulations; and assist in implementing national and sub-national environmental policies. As the level of governance is closest to the people, they play a
vital role in educating, mobilizing and responding to the public in the promotion of
sustainable development.
6
Indeed, local authorities can play a more effective role in developing the capacity to
deliver feasible sustainable development outcomes. Policies such as housing, transport,
urban development, waste and water management, have significant impacts on how
cities grow. The traditional framework of policies is not designed to consider
interrelationships between the policies of different sectors; it rather aims to focus on
each policy in an isolated manner: thus, in addition to the improvement of specific
policies, a change in the policy framework itself is required today.
This is particularly true for the urban waste management sector. Waste management
issues are at the centre of environmental concerns in many urban areas, especially
because continued population growth and the expansion of economic activities
stimulate higher consumption of resources and a greater waste generation. In these
circumstances major improvements in efficiency are needed, so as to enable the
decoupling of environmental degradation from population growth and economic
development, and to diminish environmental pressures to sustainable levels. An
effective environmental management of industrial (hazardous) and urban waste can
also serve as a significant mechanism for the creation of new job opportunities, the
promotion of renewable energy sources and the improvement of people’s quality of
life by preventing pollution in urban areas.
The real challenge is to transform waste into reusable resources: measures should be
initiated to stimulate private investment in this field and to create opportunities to
include municipalities as potential beneficiaries of the Kyoto Protocol’s Clean
Development Mechanism for curbing greenhouse gas emissions. For these reasons,
the development of clean technologies – by replacing refuse dumps with final waste
disposal centres – can be included among the advantages of responsible and sustainable
local government policy-making. In more general terms, local governments can play an
important supervisory role, enforce laws and regulations and promote initiatives suitable
for local conditions, including the adoption of specific action plans, awareness raising
campaigns and influencing the market towards the attainment of an environmentally
sound waste cycle.
Paolo Soprano
Ministry for the Environment and Territory – Italy
7
PRESENTACIÓN
El papel de las autoridades locales
para una mejor política ambiental
El curso de capacitación sobre gestión integrada de residuos sólidos urbanos a nivel
de Municipios de América Latina y el Caribe, realizado en diciembre de 2005, en Río de
Janeiro (Brasil), ha sido uno de los pasos más importantes en la fructífera colaboración
entre el Ministerio de Ambiente y Territorio – Italia y el Centro Internacional de Investigaciones para el Desarrollo (IDRC) de Canadá, a través del Secretariado de Manejo del
Medio Ambiente (EMS-SEMA). Anteriormente esta colaboración ya había logrado un importante resultado a través de la organización de una reunión de alto nivel que tuvo
lugar en San Pablo (Brasil), donde expertos, administradores, profesionales y autoridades de instituciones públicas se reunieron para cuantificar el proceso en pro de la
sustentabilidad en la gestión integrada de residuos sólidos urbanos, y para evaluar la
situación a través del intercambio de información y evaluación de las mejores prácticas en cada área.
Estas actividades destacadas – combinadas con otras que se desarrollaron en el transcurso del año – corresponden al Memorando de Entendimiento firmado conjuntamente por el Ministerio de Ambiente y Territorio – Italia y el IDRC, que entró en vigor en el
año 2005 y apunta al logro de objetivos compartidos relativos a la protección del
medio ambiente y a hacer que los mismos fueran compatibles con el desarrollo social
y económico. Este Acuerdo fija su atención en algunas áreas específicas vinculadas a
las políticas ambientales locales, como por ejemplo en los casos de gestión de residuos sólidos urbanos, gestión sustentable del agua y saneamiento, promoción de tecnologías y procesos industriales limpios y uso de fuentes de energía renovable, siendo
todos ellos procesos acometidos para asegurar un desarrollo local sustentable.
El Memorando de Entendimiento, que establece una asociación entre las dos instituciones, implica no sólo que ambas partes están comprometidas con el logro de objetivos acordados, sino que también desean poner en marcha acciones a todo nivel con la
participación de países desarrollados y en desarrollo, instituciones internacionales,
organizaciones no gubernamentales (ONG) y el sector privado. Los proyectos resultantes (en especial en América Latina y el Caribe) estarán expresamente dedicados al
establecimiento de nuevas asociaciones (en la categoría más amplia de “iniciativas tipo
II” que fueran lanzadas en Johannesburgo) en las áreas de interés entre los sectores
público y privado, o dentro de cada uno de ellos, y para apoyar a las autoridades
locales en el desarrollo de procesos voluntarios a nivel local.
En este sentido, el papel que podrían desempeñar los municipios en función del proceso de sustentabilidad es de gran importancia: la dimensión local debería ser considerada como la más significativa en la experiencia de nuevas estrategias ambientales y
mejores prácticas, mostrando su efectividad en una dimensión más amplia. Tal como
se establece en el capítulo 28 de la Agenda 21, las autoridadeslocales construyen,
8
operan y mantienen la infraestructura económica, social y ambiental; supervisan los
procesos de planificación; implantan las políticas y reglamentaciones ambientales locales; y colaboran en la implementación de políticas ambientales nacionales y sub-nacionales. A medida que el nivel de gobernabilidad se acerca más a los pueblos, las
autoridades locales desempeñan un papel crucial en la educación, movilización y respuesta al público para promover el desarrollo sustentable.
De hecho, las autoridades locales pueden desempeñar un papel más eficaz en el
desarrollo de la capacidad para producir resultados más efectivos en cuanto al desarrollo sustentable. Políticas públicas como la de vivienda, transporte, desarrollo urbano, gestión de desechos y agua, producen un importante impacto en la forma en que
las ciudades crecen. El marco tradicional de las políticas no ha sido diseñado para
tener en cuenta la interrelación entre las políticas sectoriales; más bien intenta
focalizar cada política de manera aislada: es por eso que hoy se requiere un cambio
en el propio encuadre de las políticas públicas, además de la mejora de algunas políticas específicas.
Esto resulta particularmente cierto en el caso del sector de gestión de desechos urbanos. Los problemas en torno al manejo de residuos constituyen la principal preocupación ambiental en muchas zonas urbanas, en especial porque el constante crecimiento
poblacional y la expansión de las actividades económicas estimulan un mayor consumo de recursos y un incremento en la generación de desechos. En tales circunstancias, se requiere una considerable mejora en la eficiencia para permitir la separación
de la degradación ambiental del incremento de la población y el desarrollo económico,
y para reducir las presiones ambientales a niveles sustentables. La gestión ambiental
efectiva del desecho industrial (peligroso) y urbano también podría ser un mecanismo
importante en la creación de nuevas oportunidades de empleo, en la más amplia difusión de la adopción de fuentes de energía renovable y para mejorar la calidad de vida
de las personas, evitando la contaminación en zonas urbanas.
El verdadero desafío está en transformar los residuos en recursos reutilizables: deberían preverse medidas para estimular la inversión privada en este campo y generar
oportunidades para incluir a los municipios como beneficiarios potenciales del Protocolo de Kyoto sobre Mecanismos de Desarrollo Limpio, para abatir las emisiones de
gases con efecto invernadero. Por todas estas razones, el desarrollo de tecnologías
limpias – sustituyendo vertederos por centros para la disposición final de los residuos
– podría incluirse entre las ventajas que se derivarían al contar con políticas responsables y sustentables en los gobiernos locales. En términos más generales, los gobiernos locales pueden desempeñar un papel importante en la supervisión, asegurando el
cumplimiento de la legislación y las reglamentaciones y promoviendo acciones adecuadas a las condiciones locales, incluyendo la adopción de planes de acción específicos,
sensibilización, y liderando al mercado en la dirección correcta para el logro de un ciclo
de manejo de desechos que resulte ambientalmente saludable.
Paolo Soprano
Ministerio de Ambiente y Territorio – Italia
9
PRESENTAZIONI
Il ruolo degli enti locali per
una politica ambientale migliore
Il corso di formazione sui sistemi integrati di gestione dei rifiuti solidi urbani nei
comuni dell’America Latina e dei Caraibi, tenutosi a dicembre 2005, a Rio de Janeiro
del Brasile, ha rappresentato un significativo passo in avanti a favore della fruttuosa
collaborazione fra il Ministero dell’Ambiente e della Tutela del Territorio – Italia ed il
Centro Internazionale di Ricerca per lo Sviluppo Canadese (IDRC) attraverso il proprio Segretariato per la Gestione Ambientale (EMS). Tale collaborazione aveva già ottenuto un risultato importante attraverso l’organizzazione di un incontro ad alto
livello tenutosi a San Paolo del Brasile, dove un gruppo di esperti, di amministratori, di
professionisti e di dirigenti di istituzioni pubbliche si sono riuniti per quantificare il
processo verso la sostenibilità del settore della gestione dei rifiuti solidi urbani e per
valutare la situazione grazie ad uno scambio di informazioni ed ad un esame delle
migliori pratiche di ogni settore.
Queste attività di spicco – combinate ad altre attività svoltesi durante l’anno – sono
contenute nel memorandum di intenti siglato fra il Ministero dell’Ambiente e della Tutela del Territorio – Italia e l’IDRC, entrato in vigore nel 2005, e che ha come scopo
l’ottenimento degli obiettivi comuni per la tutela ambientale e la sua compatibilità con
lo sviluppo economico e sociale. Tale accordo si concentra su settori specifici collegati alla politica ambientale locale come ad esempio: la gestione dei residui urbani, la
gestione sostenibile dell’acqua e dei servizi igienici; la promozione di tecnologie e processi industriali puliti e l’utilizzo di risorse energetiche rinnovabili, tutti finalizzati a
garantire lo sviluppo sostenibile locale.
Il memorandum di intenti, che stabilisce una partnership tra le due istituzioni, prevede
non solo l’impegno di entrambe le istituzioni al raggiungimento degli obiettivi concordati, ma anche l’attuazione di attività ad ogni livello con la partecipazione dei paesi
industrializzati e quelli in via di sviluppo, con le organizzazioni internazionali, con le
ONG e con il settore privato. I progetti che ne verranno (in particolare in America Latina
ed i Caraibi), saranno espressamente volti a stabilire una nuova partnership (nella categoria più ampia delle “iniziative di tipo II” lanciata a Johannesburg) nei settori di interesse fra il settore privato e quello pubblico, o con ciascuno di loro, e sostenere gli enti
locali nello sviluppare dei processi volontari a livello locale. A questo riguardo, il ruolo
che i comuni possono ricoprire verso il processo di sostenibilità è di estrema importanza: la dimensione locale va considerata come la più significativa per sperimentare
nuove strategie ambientali e migliori pratiche, dimostrando la loro efficacia su scala più
ampia. Come affermato nel capitolo 28 dell’Agenda 21 “gli enti locali, costruiscono,
operano e mantengono le infrastrutture economiche, sociali ed ambientali,
supervisionano i processi di pianificazione, stabiliscono le politiche e le regolamentazioni
in materia ambientale a livello locale e partecipano all’implementazione delle politiche
nazionali e sub-nazionali in ambito ambientale. Poiché inoltre essi rappresentano il li-
10
vello di governo più vicino ai cittadini, gli enti locali giocano un ruolo vitale rispetto
all’educazione, alla mobilizzazione ed alla responsabilizzazione del pubblico nella promozione dello sviluppo sostenibile.
Effettivamente gli enti locali possono giocare un ruolo più efficace nello sviluppare la
capacità di trasmettere risultati validi per lo sviluppo sostenibile. Le politiche sugli alloggi, sui trasporti, sullo sviluppo urbano, sulla gestione dei rifiuti e dell’acqua hanno un
impatto notevole sulla crescita delle città. Lo schema tradizionale delle politiche non è
atto a considerare l’interdisciplinarità fra le politiche di settore; al contrario si concentra su ogni politica in modo isolato ed è, pertanto, adesso necessario modificare lo
schema di per sé, oltre naturalmente a migliorare le singole politiche. Ciò è particolarmente vero per il settore della gestione dei rifiuti. Le questioni relative alla gestione dei
rifiuti sono al centro dell’attenzione ambientale in molte zone urbane in quanto, a
causa della continua crescita demografica e dell’espansione delle attività economiche,
si stimola un maggior consumo delle risorse ed una maggiore produzione di rifiuti. In
queste circostanze è necessario un miglioramento dell’efficienza al fine di scollegare
il degrado ambientale dalla crescita della popolazione e dallo sviluppo economico ed al
fine di ridurre la pressione ambientale a livelli sostenibili. Una gestione dei rifiuti urbani
ed industriali (pericolosi) potrebbe essere anche un meccanismo importante per la
creazione di nuovi posti di lavoro, per diffondere l’adozione di risorse energetiche
rinnovabili e per migliorare la qualità di vita della gente grazie alla prevenzione dell’inquinamento nelle zone urbane.
La vera sfida è trasformare i residui in risorse riutilizzabili: vanno presi dei provvedimenti per incoraggiare gli investimenti privati in questo settore e per creare le opportunità affinché i comuni vengano inclusi come potenziali destinatari del Meccanismo di
Sviluppo Pulito del Protocollo di Kyoto per la riduzione delle emissioni di gas ad effetto serra. Per queste ragioni, lo sviluppo di tecnologie pulite – che sostituiscano l’interramento con degli impianti per lo smaltimento finale dei rifiuti – può essere inserito fra
i vantaggi delle politiche responsabili e sostenibili dei governi locali. In termini più generali, i governi locali possono giocare un ruolo importante di regia, garantendo l’applicazione delle leggi e delle norme e promuovendo delle attività adatte alla condizioni
locali, includendo l’adozione di piani d’azione specifici; l’aumento della consapevolezza e la conduzione del mercato verso la direzione giusta per l’ottenimento di un ciclo
integrato dei rifiuti.
Paolo Soprano
Ministero dell’Ambiente e della Tutela del Territorio – Italia
11
PREFACE
There is a notably growing demand for solutions to urban cleaning issues both in
global bodies and at the level of civil society and local communities. For a long time
these issues have been relegated to the background but diverse governmental and
civil society sectors are now mobilizing to address the problem due to several areas
being affected: disease transmission and therefore public health, water course and
aquifer contamination in the environmental field, social concerns relating to
segregators, in particular children living on rubbish dumps, and pressures deriving
from tourist activities. Another aspect of urban cleaning that has more recently come
to the fore is the issue of the final disposal of solid waste in relation to Clean
Development Mechanisms.
In several situations negative impacts relating to solid waste are fundamentally
associated with inappropriate management. Changing this state of affairs involves not
only a mobilization of resources and improvements in technical knowledge of the
appropriate processes and technologies for each reality, but principally the creation
of instruments that incorporate and structure integrated management models as a
fundamental strategy to achieve a healthy city.
Deep behavioural change is necessary in order to reverse traditional policies and
practices and establish strategies that incorporate the following elements:
!
the reduction of consumption, wastage and waste generation by citizens;
!
the universalization of urban cleaning services;
!
environmentally appropriate treatment and final disposal practices;
!
the withdrawal of children from rubbish dumps;
!
the potential generation of work and incomes related to waste, promoting the social
and economic inclusion of segregators.
This Manual on Municipal Solid Waste Integrated Management is aimed at contributing
to an improvement in the technical capacities of the public sector, agencies, companies,
NGOs and civil society to deal with aspects of integrated solid waste management in a
sustainable way.
It deals with subjects that are fundamental to the understanding and improvement of
urban cleaning systems and services and covers technical and administrative issues,
questions relating to the preparation, storage and final disposal of waste, as well as
institutional, economic, political, social and legal aspects, including clean development
mechanisms.
Acknowledging that the main responsibility for providing urban cleaning services falls
on the municipal level of government, the Manual provides guidelines that serve as a
reference for decision-makers in the formulation of public policies and corresponding
legislation.
12
The Manual has been prepared by professionals with long-term experience in this
sector who also serve as teachers in the courses offered by IBAM. As part of their
work methodology a preliminary version was examined by participants in the first IBAM
training course, held in December 2005 with representatives from several Latin American
and Caribbean countries, and was subsequently revised and completed. It is intended
for use as a basic didactic instrument that can orientate future workshops.
It is essential that municipal teams in charge of the planning and operation of services
are properly equipped to prepare and implement programs, plans and initiatives geared
to improving urban cleaning systems, including institutional adaptations that are
necessary for the administration of services and the allocation of available resources
in a responsible way, using appropriate technologies and methods and respecting the
particular economic social and cultural circumstances of the local population.
Within this perspective the Manual’s objective is to be a useful tool in integrated
administration training for all those who work with solid waste and to be sufficiently
flexible so that from all the information provided on different forms of “know how”
that which is most useful for application to the particular conditions of each city can
be chosen. You are therefore invited to consider and use the solutions offered by
this Manual.
Tereza Cristina Baratta
Director, National School of Urban Services – IBAM
13
1
14
The general situation of solid waste
management in Latin America and
the Caribbean
1. The general situation of solid waste management in Latin America and the Caribbean
1.1
Introduction
In the municipal solid waste management sector, an evaluation made during a certain
period has only a relative value as the quality of services can change very quickly.
A well administrated landfill can became a rubbish dump in a few days if a tractor stops
functioning due to some defect that the municipality is not able to quickly repair because
of slow bureaucratic processes involved in buying spare parts or contracting a
maintenance service. Even if the system is in the hands of a private company, through
outsourcing or concession contracts, an interruption in the payment of bills by the
municipality can paralyze services.
However, a periodical analysis of the state of solid waste management services in
several cities of a country can indicate the general trend, which is significant for
answering the question: is waste management improving in Latin American cities?
In practically all Latin American countries urban cleaning services are the responsibility
of municipalities and often a well functioning system in a particular city does not
necessarily reflect the trend in the country as a whole but rather the mayor’s
determination to solve the problem. However, if a study includes a wider range of
cities, a better evaluation can be made of trends both in service quality and the types
of approach to the issue employed by municipal, provincial and national governments
in each country.
The most recent update of the Report on the Regional Evaluation of Municipal Solid
Waste Management Services in Latin America and the Caribbean, which covered the
entire region, was carried out by the Pan American Health Organization (PAHO) in 2005.
As it is the best document produced up to now on this subject, its executive summary
is transcribed here.
1.2
Regional Evaluation of Municipal Solid Waste Management
Services in Latin America and the Caribbean 1
The Pan American Health Organization (PAHO) in support of Latin American and Caribbean
(LAC) governments, and taking into consideration the significant role performed by
urban sanitation services to reduce health risk factors and environmental impacts,
coordinated the Report on the Regional Evaluation of Municipal Solid Waste Management
Services with the direct participation of public institutions and private agencies, as well
as NGOs involved in solid waste management in countries in the Region.
The Solid Waste Evaluation constitutes a first regional effort in which 36 LAC countries
participated within a common evaluation strategy. The collection of information for
1.
Based on Diagnosis of Municipal Solid Waste Management in Latin America and the Caribbean, IADB and PAHO, 1997; updated
in the form of “Report on the Regional Evaluation of Municipal Solid Waste Management Services in Latin America and the
Caribbean", 2005. (www.paho.org and http://www.bvsde.ops-oms.org/bvsars/fulltext/informeng/informeng.htm).
15
the Evaluation took place in the countries between 2002 and 2003 through a national
coordinating group of representatives from national and local entities involved in solid
waste. The information was obtained through a series of forms that collected basic
demographic, health, education and socioeconomic data from the country and specific
indicators related to urban sanitation services referred to the year 2001. The information
was complemented with an analytical report for the country executed by each country.
The Solid Waste Evaluation proposal emerges from the need to have a frame of
reference that makes the solid waste sector visible in LAC to identify their needs and
possibilities within the comprehensive management concept guided towards improving
the communities’ quality of life. Within this context, the purpose of the Regional
Evaluation is to generate and expand the knowledge of the current situation, which is
critical in many countries, as can be seen by the alarming environmental deterioration
and the sanitary problems related to unsafe solid waste management and the scarce
attention given to this area, mainly to the final disposal of waste with the purpose of
looking for solutions or alternatives at a national and local level to improve the current
situation and be able to accomplish waste management that is truly efficient.
Even though it is true that moderate progress has been made as a result of national
and international initiatives, among which Agenda 21 stands out – agreed upon in 1992
in Rio de Janeiro during the United Nations International Conference on the Environment
and Development – comprehensive solid waste management still represents one of
the most important challenges that national and municipal governments face, as well as
service providers and the community in general. The life styles, the high levels of
consumption, the materials used in industrial production and the introduction of
Figure 1 – Disordered settlement and informal market close to a rubbish dump
16
1. The general situation of solid waste management in Latin America and the Caribbean
persistent materials in daily human activities, tend to increase the volumes of solid
waste, representing serious problems for its collection, transportation, treatment and
final disposal.
The intensive migration of indigent populations from rural areas to medium and large
cities has created outlying poverty belts, of which the majority lack public service
infrastructure and have completely spread out in a disorderly manner without any urban
planning. In addition, the economic and social impoverishment present in these
settlements, takes many families, mainly women and children, to find in garbage, in the
streets, as well as in final disposal sites, their only means for survival.
The Solid Waste Evaluation estimates that by the year 2001, the LAC population reached
518 million of which 406 million (78.3%) is urban and generates around 369,000 tons of
municipal solid waste daily, of which 56% is generated in large urban centers, 21% in
medium size urban centers and 23% in small urban centers. Approximately half of the
waste generated in LAC is produced by medium and small centers, which tend to have
more difficulty in waste management, the impact to the environment being considerable
since the disposal of these wastes is usually deficient. Just a few of the LAC countries
have comprehensive plans or programs to respond to the sector’s demands. As a
consequence, necessary strategies or components that will allow for the guidance,
regulation and institutional development of the municipalities as sanitation service
providers, as well as the due training of human resources and the capitalization of
financial resources are not proposed.
The Solid Waste Evaluation confirmed the information gaps that exist in the solid waste
area in the countries of the Region. Practically all of them, institutions and organizations
that are involved in this area, manage insufficient information. These gaps are seen
not only at a local level, where they are more evident, but also in institutions at a
national level in charge of defining policies and assigning resources.
Waste collection coverage in the Region varies from 11%-100% with a regional average
of 81%, although with great differences within the countries, more noticeable in medium
and small populations, in which only 69% of the population has collection service.
Adequate sanitary final waste disposal coverage (landfill) for the LAC Region is 23%,
which makes it evident that there is a serious environmental and health problem due
to the proliferation of open air “dumps.” This means that of the 299,000 tons collected
daily in the Region, around 230,000 tons of waste are indiscriminately deposited in the
environment, at best in dumps with an uncertain control. It is presumed that the
remainder, which is not collected, is burned or dumped without any control in vacant
lots, streets, highways and waterways contaminating the environment and endangering
the population’s health. The situation worsens with the lack of adequate hospital and
hazardous waste management, mainly when they are dumped together with municipal
waste, a common practice in several countries in the Region.
The Solid Waste Evaluation shows that average regional generation of residential solid
waste per capita reaches 0.790 kg/inhab/day, with a noticeable fluctuation in countries
17
with a low Human Development Index (HDI). There are cases in which the per capita
generation does not exceed 0.250 kg/inhab/day, yet, in countries where tourism is an
important economic factor, the per capita generation reaches 2.400 kg/inhab/day. With
regards to municipal waste, the per capita generation varies between 0.370 kg/inhab/
day to 2.650 kg/inhab/day with a regional average of 0.910 kg/inhab/day. Likewise,
large cities are the largest generators of municipal waste per capita with close to 1.100
kg/inhab/day while the small and poor settlements in Latin America generate an average
of less than 0.500 kg/inhab/day.
These facts show that economic growth and the level of consumption have a great
influence in solid waste generation, and consequently, demand a more efficient
management of urban sanitation services, mainly regarding sanitary final disposal.
The LAC countries are in different stages of development in the solid waste sector.
At national levels, health and environmental ministries have been evolving to replace
the governing of the sector and the regulation of services to a certain point.
At a local level, municipalities maintain responsibility for services, but with differing
operational modalities: direct public sector administration, outsourcing and the granting
of concessions. The private sector has been becoming ever more prominent, not only
in providing urban cleaning services but also in investment in solid waste sector
development.
Several deficiencies are observed in guiding the sector, and therefore, in its planning
and programming at medium and long term. Municipalities, specifically the smaller ones,
lack management and financial capability, which does not allow for the demands of an
adequate solid waste management.
With regard to the legal aspects applicable to the sector, great gaps can be observed in
the judicial development and in different instruments for their compliance. Even though
there is an abundance of environmental laws, they are scattered in several legal bodies.
This produces an overlapping effect and inconsistencies, which makes it difficult to
implement follow-up mechanisms, control and sanctions. Therefore, the effectiveness
of current legal tools are minimized, even when several countries are developing
specific laws and regulations for municipal, as well as hazardous waste, as is the case
in Bolivia, Ecuador, Mexico and Peru, among others.
The costs for urban sanitation services in the Region fluctuate between US$15 and
US$105 per ton, with an average of US$29 per ton for collected, adequately disposed
of and treated waste. The breakdown of these costs corresponds to sweeping,
collection and urban sanitation in main streets, transfer, treatment and final disposal.
18
1. The general situation of solid waste management in Latin America and the Caribbean
The cost breakdown indicates that the highest cost corresponds to sweeping and
waste collection and transportation, representing between 60% and 70% of the
total cost.
Investments in the sector are minimal compared to other public services such as
electricity, potable water and basic wastewater, and concentrate in acquiring equipment
and, lastly, in infrastructure works for final disposal.
In the majority of Latin American countries, financial support for this service is received
through the collection of a municipal rate. This general rate is not exclusively assigned
to the urban sanitation service, but it is part of other services such as public lighting,
real estate taxes and others. The monthly average rates for residential waste in LAC
reaches US$2.5 per user, a value that does not cover the cost for urban sanitation
services, which reflects a deficit of close to half the real cost of those services. In the
English speaking Caribbean countries, urban sanitation services are strongly subsidized
by the central government, through a consolidated fund formed by different
environmental taxes.
The formal segregation and recovery of recyclable materials is not carried out on a
large scale in LAC. On average, the Evaluation showed that only 2.2% of the materials
are recovered from garbage, of which 1.9% is for inorganic recycling and 0.3% to organic
waste recycling, mainly made up of food and garden waste. Informal recycling is widely
promoted in Latin America and its magnitude is difficult to identify due to the fact that
the activities are subtle. Informal segregation has increased in countries that have gone
through a rapid and deep economic crisis as a result of the increase in poverty and
unemployment, coupled by the lack of initiatives to integrate this form of subemployment into the solid waste sector.
The inadequate management of solid waste has serious consequences in the
environment and the health of the population, mainly those who are in contact with
wastes. This is the case of the personnel who work in this sector. The majority do not
have the minimum prevention and occupational safety measures. The situation is more
critical for individuals working and living from the recovery of materials from waste,
who work under unsanitary and subhuman conditions, among which there is a significant
number of women and children. Although the direct casualty has not been determined,
several diseases are related to wastes when the conditions conducive to the
development of several disease agents are present.
The direct and indirect environmental and social costs that represent the production,
handling and inadequate disposal of waste to the community are growing and are
significant. The environmental impacts are mainly revealed in the contamination of
surface and underground waters for public supply and the obstruction of drainage
canals due to the uncontrolled dumping of solid wastes in bodies of water.
19
Other important impacts that affect human health are the emission of air contaminants
due to open air burning; the incineration of waste without adequate control equipment;
the transmission of pathogen microorganisms through water; by food; the breeding of
bovine and porcine livestock with contaminated organic waste; as well as vectors that
transmit diseases. These are in addition to aesthetic and nuisance impacts due to noise
and bad odours.
Figure 2 - Environmental degradation caused by a refuse dump
In several countries in LAC, the participation of small companies and private micro
companies in solid waste collection has been increasing more and more, mainly because
this means a more economic alternative for the municipalities and/or sanitation municipal
companies. The advantages of these companies resides in the intensive use of labour
force, the use of very low cost technologies that use animal, human or mechanic
(tricycles) traction and the promotion of greater community participation to facilitate
the material collection and separation operation at the generation source.
The community has a limited participation in solid waste management in LAC.
Community participation occurs mainly when there is support from NGOs and a strong
educational component. Such participation is key to put into practice activities that
take into consideration the principle of the three “R’s,” reduction, reuse and recycling,
and at the same time is supported by a strong national political base that guides the
solid waste sector.
Technological and research development in relation to solid waste is reduced in the
majority of LAC countries. The contribution in research and technological development
from institutes and universities for the solid waste area is scarce. The training of human
resources in the solid waste area is usually carried out in some universities in the
Region as part of the courses related to sanitation engineering and environmental
sciences. This is complemented with a great variety of courses, workshops and seminars
focused on solid waste management.
20
1. The general situation of solid waste management in Latin America and the Caribbean
Initiatives such as primary environmental care, healthy municipalities and communities,
health-promoting schools and other health promotion strategies are basic to coordinate
initiatives with the capacity to maximize participative management that includes the
community, local government, NGOs and the private sector with the purpose of
establishing healthy policies, create healthy environments, promoting healthy life styles,
personal capacity building through education and empowerment, especially in school
and Ecoclub environments on solid waste management topics. These initiatives offer
great potential for establishing long lasting activities and allowing the use of shared
experiences through community networks and alliances with different institutions that
share a common interest.
The management aspects of the sector, regulations and operation of solid waste
management services, institutional and functional organization, financial self-sustainability
and the participation of the private sector and the community, should be carefully
evaluated in each of the countries to determine the appropriate steps, within the real
possibilities of the countries, to achieve the proposed national and municipal goals.
Figure 3 - Correct landfill operation resulting from public administration commitment
The solid waste sectoral analysis will continue being a key instrument in this aspect by
providing a comprehensive vision of the sector, therefore, allowing more efficient
approaches and alternatives for their development.
Taking into consideration that solid waste management is a local activity, national and
provincial governments should provide more support to municipalities, especially those
which have scarce managerial capability and limited resources, in which the lack of
information is more significant.
21
Likewise, international cooperation has a broad field of action, especially in institutional
capacity building and in the identification and support of sectoral investments. The
commitment and will of the governments and financial organizations, and technical
cooperation to guide their efforts towards the achievement of the Millennium
Development Goals 2 open new opportunities to promote and coordinate national and
international activities to improve solid waste management in the Region.
1.3
Solid waste sector trends
The above summary of solid waste management in Latin America and the Caribbean,
based on Solid Waste Evaluation together with other studies and experiences in this
field, makes it possible to identify general sector trends. The issues dealt with below
can present variations between one country and another and between one city and
another depending on the greater or lesser degree of both commitment by mayors
and community participation.
Public awareness of the importance of urban cleaning services and
municipal solid waste management
In almost all LAC countries there has been an increase in community awareness of the
need for improved solid waste management. The principal causes of this increase are:
!
the growing occurrence of environmental problems that affect people’s daily life
and the dissemination of information about them through the media;
!
the perceived relationship between solid waste management and the wellbeing and
health of citizens;
!
the increasing cost of services, especially where universal coverage is sought in the
urban zones of a municipality, which demands a more professional management by
the municipal administration;
!
the widespread exposure in the media of problems in developed countries caused
by defective handling of hazardous industrial waste or its inappropriate final disposal
and the resultant damaging effects on the health of the population.
Circumstantial differences in service provision between small municipalities
and large or medium-sized cities
A gradual improvement in solid waste management can be found in large cities, not
only in collection services but more so in final disposal. Municipalities with a population
of over 200,000 have more financial resources and capabilities to deal with the
difficulties involved in maintaining sustainable solid waste management.
2.
22
For more information consult http://www.un.org/millenniumgoals.
1. The general situation of solid waste management in Latin America and the Caribbean
In small urban centres, the category into which most Latin American population centres
fall (in Brazil, for example, 80% of municipalities have less than 30,000 inhabitants),
urban cleaning services are limited to collection, for the most part regular, in zones
where inhabitants can influence public policy (commercial and high income residential
zones) and final disposal takes place in one or more open air dumps without any
sanitary or environmental control.
Larger municipalities generally have a department of urban cleaning, but smaller ones
often only have one person running these services and for essential material resources
depend on departments with other functions.
The importance of political will
Sound solid waste management in Latin American cities depends to a large extent on
the mayor’s commitment to this issue. If the mayor does not consider it to be a priority
sector, budget resources will not be allocated to it, service coverage will not be universal
and service quality will not be satisfactory.
It is evident that with easier access to information and its dissemination through the
internet, those responsible for municipal services have to pay more attention to the
waste issue and are less able to ignore the problem. Only when pressured by society
and environmental control bodies do municipal administrations eventually become more
aware of the problem and begin to allocate more resources to the sector, thus
improving coverage and service quality.
The legal framework
Some large municipalities are establishing norms for solid waste management through
municipal regulations or mayoral decrees and some countries are endeavouring to
develop a national solid waste policy, but these initiatives are sometimes hindered by
political and economic interests that delay their implementation.
Although the legal framework is important, it is not the only requirement for the
achievement of good quality solid waste management. In order for legislation and norms
to translate into an improved solid waste management service a formal commitment by
the mayor to their application is necessary. The training of municipal personnel in the
preparation of tender specifications and contracts is a critical element for an efficient
initiation and operation of contractual relationships with private counterparts, NGOs,
cooperatives, etc.
Carbon credits and the clean development mechanism
The Clean Development Mechanism (CDM) allows developing countries, a classification
into which all Latin American countries fall, to obtain resources through the reduction
of greenhouse gas emissions from their industrial or urban activities.
23
Many mayors regard the timing of the arrival of carbon credits as opportune for providing
financial support for municipal endeavours to improve solid waste management services.
The resources obtained from the sale of Emission Reduction Certificates (ERC) will
not guarantee the operation of urban cleaning services, but with the dissemination of
information on how this mechanism functions, municipal administrations will know how
to maximize its economic advantages to fulfil municipal needs. Nevertheless it must be
remembered that such benefits from the Kyoto Protocol Clean Development Mechanism
are in effect only up to 2012.
Composting
Composting is a procedure that is increasingly applied in developed countries due to
the prohibition of organic matter dumping in landfills, and is now reappearing in
developing countries. This system, which can be operated manually in small towns or
be mechanized where large amounts of waste have to be processed, offers the great
advantage of reducing the generation of leachate instead of producing biogas in landfills,
and in addition prolongs the latter’s useful life.
A complementary advantage of a composting system is that it can contribute to the
viability of establishing and operating a medium or large size plant by generating income
through the sale of Emission Reduction Certificates. This is so because there is an
already existing methodology, tested by the Intergovernmental Panel on Climate Change
(IPCC), that has determined that composting does not merely reduce but avoids the
emission of greenhouse gases as organic matter in aerobic decomposition only gives
off carbonic gas and water and not methane, which is the harmful gas that would be
generated in a landfill if the organic matter was deposited there.
Difficulties involved in the establishment of new landfills
PAHO’s diagnosis confirms that one of the weak points of solid waste management
systems in Latin American cities is final waste disposal. As mayors become increasingly
aware of the seriousness of this problem, refuse dumps are beginning to be closed or
converted.
In such cases the municipality must decide whether to establish a landfill in the same
place, where people are already accustomed to refuse disposal, or to begin one from
scratch in another place. The latter option has presented such serious problems that
the construction of several new landfills has had to be suspended in response to the
reaction of the local community, not to mention the difficulties involved in obtaining
environmental licenses for new sites.
Municipal administrations or contracted companies offer compensation to local residents
but this is not always accepted. In many cases these problems result in municipalities
continuing to operate rubbish dumps and abandoning the establishment of new
installations for the final disposal of waste collected in the city.
24
1. The general situation of solid waste management in Latin America and the Caribbean
Communities have also reacted negatively to the establishment of new transfer stations
on the grounds that in general landfills and other urban cleaning installations are poorly
managed. It is necessary to convince local residents that a well managed landfill can
exist relatively close to houses. This is a long process and satisfactory results will
depend on the provision of numerous examples until residents become convinced
that it is possible.
Informal segregators and formal selective collection systems
Due to the growing unemployment that is found in almost all Latin American cities,
especially the larger ones, more and more people resort to the streets in search of
some means of survival. The last hope is recyclable waste that can be found amongst
the refuse.
On the one hand this activity has positive aspects: waste can be a source of income
for these people who do not have any other way of surviving and their work removes
a significant amount of material from the urban cleaning circuit, and therefore reduces
the costs of collection, transfer and final disposal, as well as extending the useful life
of landfills. On the other hand, the segregation of materials is often done in a disorderly
way, with bags of domestic waste being opened, materials that can be commercialized
separated and the waste that the segregator is not interested in is left scattered on
the street, which produces serious problems and much more work for the sweeping
services.
In addition municipalities that are implementing formal selective collection systems are
facing difficulties in that before the truck passes to collect the recyclable waste, the
street segregators have already taken it.
Even where the recycling system is institutionalized with the participation of segregator
organizations, other independent segregators compete in the streets with the formal
system. This phenomenon is happening in almost all large and medium-sized cities in
Latin America and the prognosis is that it will increase.
In many South American cities segregators working in rubbish dumps or landfills react
forcefully when the municipality attempts to implement the closure of the site and
begins a new landfill where their activity will not be allowed. This resistance on the part
of segregators is due to the danger of them losing their only source of income, while
the public authority is not able to create hundreds of jobs overnight or provide programs
that generate income to replace that gained from segregation activity in landfills and
the streets. This situation will continue while unemployment remains one of the principal
scourges of Latin American countries.
25
Contract types
Municipal administrations face two big challenges in relation to solid waste management
in Latin American cities: to provide a universal service and to improve its quality.
As municipal budgets are finite, mayors are beginning to look for more effective and
less expensive service provision models and are increasingly contracting work. As a
result, most large and medium-sized cities outsource collection, transfer and final
disposal operations thus transferring to the private sector the burden of investment
and operational costs.
The municipality for its part takes on the monthly payment of bills for services rendered
and the coordination and supervision of such services. In recent times some large
cities have contracted services with long term concessions, especially for the
establishment and operation of large sanitary landfills that require significant investment
and therefore a longer period to see a return on it. In general this has proved to be a
satisfactory solution, provided that the specifications are reasonable and the tender
process respects the limits required by law and administrative probity.
Economic sustainability of the sector
In general, a municipality’s income from rates or specific tariffs is nowhere near enough
to cover the costs of urban cleaning services. The incidence of payment arrears is high
and there is not much that can be done to reduce it as an interruption of collection
services would only reduce the cleanliness of the city as households that do not
receive this service would find another, no doubt inappropriate, way of disposing of
their rubbish.
This constitutes one of the main impediments to good quality service management as
municipal administrations have to allocate monies from their budgets for urban cleaning
services without a corresponding income from rate or tariff collection, a state of affairs
that is detrimental to other municipal services.
Money raised together with national governmental or multilateral bodies for investment
in equipment such as collection trucks or in the construction of installations such as
landfills, usually does not solve this problem. The resources needed for the maintenance
of sound and sustainable urban cleaning operations have to be allocated from the
municipal budget and this represents the biggest challenge faced by administrators,
but success is dependent on the mayor’s level of commitment and political will to
prioritize the issue.
The trends of change
Many municipalities are training their technical personnel and seeking resources from
provincial or national bodies with a view to improving service quality. This is due not
26
1. The general situation of solid waste management in Latin America and the Caribbean
only to the increased awareness of both mayors and the general public about the
significance of this issue, but also to the improved performance of environmental
control bodies and national ministries that oversee municipalities’ compliance with their
legal obligations. As a result, municipal administrations are signing agreements that
establish periods within which service provision has to reach specified levels of quality
and coverage. There is now an unprecedented level of attention and debate on municipal
solid waste management and a seemingly inexorable search by municipalities for models
that are sustainable from both a socioeconomic and environmental perspective, with
the help, even if sporadic, of provincial and national governments.
27
2
28
Integrated solid waste management
2. Integrated solid waste management
Latin American and Caribbean cities present great regional and local imbalances, which
call for the establishment of new concepts, frameworks and practices in regard to
solid waste management. Typical situations are:
!
high technology industrial processes aimed at competitive insertion in global markets
side by side with obsolete industrial processes that produce significant
environmental damage;
!
consumption pockets having a pattern associated with high levels of refuse
production equivalent to that of developed countries together with large sectors
of the population who do not have access to consumer goods;
!
the availability of waste processing technologies together with a lack of the financial
and human resources necessary to maintain them and the presence of large groups
of segregators in streets and rubbish dumps.
Traditional practices, generally insulated, address the problems of solid waste in a partial
way, dealing only with the management of the system, treatment plants and final
disposal. It is of fundamental importance to also take into consideration the generation
of waste, the sustainability of systems and the role of citizens as generators,
consumers, recyclers and managers, in order to establish a shared concept in which all
win and positive socio-environmental outcomes are produced.
The concept of integrated solid waste management considers the entire cycle including
production, consumption, discarding and final disposal. In practice this concept ranges
from the minimization of waste generation in the production process, including
packaging, to the maximization of its reuse through the implementation of more
appropriate collection systems for each situation and the employment of treatment,
recovery and recycling processes and technologies. In this way only waste with no
utility is left for final disposal.
It is important to emphasize the significant differences between traditional and
integrated approaches to this subject: in the latter waste is always regarded as a
raw material for the production of new products through reuse, recycling or
recovery. Waste therefore has a commercial value that can be added to the
production chain thus creating new work opportunities and generating income for
various sectors of society.
The optimization of these circuits reduces to a minimum the amount of waste for
final disposal. The reduction of waste to be collected, transported and disposed
of in landfills – which as a consequence will occupy smaller areas or will have a
longer useful life – contributes to the economic and environmental sustainability
of systems.
This is the approach recommended by Agenda 21: the transformation of the production
and consumption matrix on the basis of the 3R’s – reduce, reuse and recycle – to which
has now been added a new R for recover, as a result of which they are now called the
29
4R’s. This model has been used as a tool to solve problems arising from the increasing
amounts of solid waste generated by the industrial society.
“Environmentally sound waste management must go beyond the mere
safe disposal or recovery of generated waste and seek to address the
root cause of the problem by attempting to change unsustainable
patterns of production and consumption. This implies the application
of the integrated life cycle management concept, which presents a
unique opportunity to reconcile development with environmental
protection.” (Agenda 21, chapter 21)
Putting these criteria and the concept of integrated solid waste management into practice
in Latin American and Caribbean cities requires the development of local participation
processes.
Participation processes allow the different stakeholders to identify opportunities that
can lead to solutions for the problems presented by solid waste, through the
development of an Integrated Solid Waste Management Plan (ISWMP).
Usually it is recommended that these plans are developed at a municipal or local level.
However it is possible for a group of municipalities to develop them and share some
solutions especially for the final disposal of waste. Plans can also be formulated at a
regional, provincial, or in the case of smaller countries, even national level. On whatever
scale they are made, ISWMPs must be complemented by national and regional policies
on this issue.
Some elements are essential for the development of integrated solid waste management
(ISWM) processes:
!
the participation of all public, private and community stakeholders in the conception
and planning of processes and solutions, and in the implementation of an urban
cleaning system;
!
the integration of all elements of the solid waste cycle in the 4R’s processes;
!
the integration of technical, environmental, social, juridical, institutional and political
aspects in order to guarantee system sustainability;
!
the articulation of proposed solid waste systems with overall urban planning and
other urban systems, particularly environmental sanitation, including water provision,
sewerage systems, rainwater drainage and vector control.
Integrated management depends on the functioning of specific sub-systems that involve
installations, machines, labour and technology, not only provided by the municipality
but also by other agents participating in the management, amongst which are:
!
citizens themselves, responsible for the separation and differentiated pre-collection
storage of recyclable materials and other domestic waste;
30
2. Integrated solid waste management
!
large generators, responsible for their own waste;
!
segregators organized in cooperatives, responsible for separating recyclable materials
discarded by citizens and selling them to the relevant companies;
!
health institutions with an internal management of infectious waste that either
sterilizes it or appropriately separates it by type for differentiated collection;
!
the municipality, that through its agents, institutions and contracted companies, and
by means of contracts, agreements and cooperation accords, plays the principal
role in the integrated management of the entire system.
In addition to the technical and financial aspects of conventional urban cleaning systems
and final disposal systems, integrated solid waste management prioritizes the social,
environmental and political-institutional dimensions and system sustainability. In order
to guarantee sustainability from a multi-disciplinary and trans-disciplinary perspective,
specific approaches must be promoted in each related field:
Social – community participation and quality control; environmental information
dissemination and education as instruments for the transformation of personal and
collective production and consumption patterns; and the social inclusion of segregators
who have to be organized, valued and associated in the solid waste production chain,
thus generating income and jobs.
Environmental – the development of clean technology for application to solid waste;
a rational use of natural resources taking into account waste minimization; reusable
material recovery; and appropriate treatment and final disposal.
Economic-financial – an analysis of system costs and the possibility of minimizing them
in order to make systems economically viable; the recovery of operational costs through
differentiated charge mechanisms according to generator profile and payment capacity.
Political-institutional – the integration of public authorities and other stakeholders
and institutions with a clear delimitation of responsibilities; the formulation of specific
policies for solid waste management; the implementation of juridical instruments and
ISWMPs, including the possibility of consortium solutions.
Technical-operational – the establishment of a specific department and the
appointment of responsible personnel; the definition of training programs; the
determination of the appropriate technology for each situation; the provision of
sufficient capacity in machines and labour to provide universal coverage in public urban
cleaning services, irrespective of the socioeconomic level and ethnic origin of the
population.
31
3
32
Institutional models and payment
for services
3. Institutional models and payment for services
3.1
Concept
A city’s urban cleaning system should be institutionalized on the basis of an integrated
management model that, to the maximum degree possible, has the capacity to:
!
foster the economical sustentability of operations;
!
protect the environment;
!
protect inhabitants’ quality of life;
!
contribute to the solution of socioeconomic problems related with the issue.
The municipal solid waste management model not only has to allow for the participation
of the community but also specifically facilitate it in order to generate public awareness
of the different activities involved in the system and its implementation costs, and
induce an acknowledgment by citizens of their role as consumers and therefore as
generators of solid waste.
Such participation would directly result in a reduction of solid waste generation, cleaner
streets, the appropriate preparation and storage of waste for collection and
consequently a cheaper operation.
It is important that citizens know that they are the ones who are paying for the system
through taxes, rates or tariffs. In summary, community participation is a key element in
the sustainability of the system while the municipality is responsible for establishing
an integrated management that necessarily includes awareness raising programs for
citizens who will then perceive that the political will to prioritize municipal solid waste
management exists.
This priority must be considered in the definition of municipal fiscal policy, which has
to be technically and socially just, and in the subsequent budget allocation to the
system that should include provision for environmental education and the development
of programs that generate income opportunities and employment.
Policy making is based on the participation of social leaders, private companies, and
public institutions active in the city and having significant environmental responsibilities.
Policy instrumentation will be structured through the approval of urban cleaning
regulations whereby the city legitimizes the adopted management model and social
obligations, and defines infractions and their respective fines. Such regulations must
clearly reflect the objectives of the public authority and raise public awareness in
regard to appropriate urban solid waste management and environmental problems.
33
3.2
Forms of administration
In general the municipality is, directly or indirectly, responsible for organizing and
providing essential local services and is therefore responsible for urban cleaning
services.
A public service is an activity undertaken by a public body with a view
to satisfying a public interest need.
What characterizes a public service, and distinguishes it from other
economic activities, is that it is essential for the community and
therefore its provision represents an obligation for the public
authority and its management is subject to the legal principles
specifically related with the efficient provision of service to the
community.
Public services are all material activities assigned by law to the State
for it to exercise, directly or through delegates with the objective of
effectively satisfying collective needs, under a partially or totally
public regime.
Urban cleaning systems can be administered in different ways:
Direct municipal management
In this case the provision of urban cleaning services is the responsibility of a municipal
department or body.
This model is generally used in smaller cities that do not have a volume of service
provision that is attractive to the private sector.
Except where they have been resolved in particular cases, the chronic problems inherent
to this model are: insufficient budget, inevitable bureaucracy, low degree of training,
political interference and frequent crises in the service. The negative results of this
group of difficulties are: a dissatisfied public, sanitary and environmental problems,
and indeterminate service costs.
Autonomous authority
This modality involves the creation of a public company specifically for the administration
of urban cleaning.
This model is more flexible than direct municipal administration and is more compatible
with the dynamic of daily urban cleaning tasks. It also facilitates greater management
autonomy, the creation of a specialized labour force and better conditions for budgetary
planning.
34
3. Institutional models and payment for services
Positive examples of urban cleaning administration by municipal public companies
can be found in some cities in Ecuador, Colombia and Costa Rica with populations of
no more than 500,000. In these cases the companies have several responsibilities
including planning, supervision and the charging of tariffs for services provided. In
addition, they have the necessary flexibility to adopt appropriate alternatives for the
provision of some components of the service, including sweeping, treatment, final
disposal and the recovery of energy from waste by generating biogas and in some
cases selling carbon credits 3.
This model is only appropriate for large cities as it requires the creation, organization
and equipping of a new specialized structure in the municipality.
Outsourcing
In this model a private sector company is contracted to undertake an activity, with a
predefined mechanism of payment based on the specific services to be provided and
technical-administrative convenience. Outsourcing is based on the concept of public
administration undertaking the functions of planning, coordination and overseeing while
the private company is responsible for operations.
It should be emphasized that service outsourcing can be employed on different scales,
from contracting well structured companies, specialized in certain types of operation
such as landfill management, to contracting micro-companies or independent workers
who undertake waste collection with carts pulled by animals or the manual operation
of small-sized landfills, for example.
Outsourcing, if well planned at every stage – from specifications in the bidding phase
to the overseeing of operations – can make a large contribution to the municipal
administration’s ability to improve the quality of services provided to the public, especially
in regard to the speed of response to operational requirements (for example the
purchase of spare parts for collector vehicles).
In many LAC cities outsourcing is employed for urban cleaning services with sweeping
and/or collection often undertaken by small civil society organizations. Some functions
are undertaken by NGOs, workers cooperatives or small companies through contracts
established by municipalities. All these cases of delegating state functions to civil society
authenticate outsourcing as an efficient practice.
Concessions
In this modality the concession holder plans, organizes, implements and coordinates
the service, and can even outsource operations and collect payments directly from
users/beneficiaries of the service.
3.
Integrated Solid Waste Management Workshop organized by IDRC in Sao Paulo, Brazil, 2005.
35
This management model is adopted in special situations where the public authority
does not have the necessary technological or budgetary resources to implement
interventions or finance the significant investments that are indispensable in dealing
with problems related to municipal solid waste management in general or a particular
aspect of it.
In general, concession contracts are long term to allow for a return on investments in
the system through tariffs charged to users. However, significant difficulties lie in the
limited guarantees that concession holders receive in regard to the collection of payment
for their services and the problems that municipalities have in preparing tender
specifications, calculating costs and overseeing services.
This type of modality has proved ineffective for collection services, but has been
widely employed with relative successs in landfill management, although it functions
less well when applied in small cities.
Free market
This model can be applied for example to large-scale solid waste generators when
municipal regulations have defined the maximum quantities permitted for collection by
the common domestic collection system and have established that large-scale generators
have an obligation to contract, at their own expense, authorized companies for the
collection of excess waste.
It can also be applied to the collection of construction rubble and other civil construction
waste in order to alleviate the burden on the public system.
Consortium
A consortium results from an agreement between municipalities with the objective of
achieving established common goals. All of each municipality’s human and financial
resources available for a certain initiative, program or project are combined in a
consortium to facilitate its implementation.
Any of these alternatives, or any combination of them, has to be selected on the basis
of both low cost and environmentally sound technique and with a view to establishing
a self-sustainable system that is resistant to changes of administration.
In the case of public services that are delegated to third-parties through concessions,
the issuing authority keeps the ownership of the service and the right to oversee it,
which implies a need for technical and administrative training in order to undertake the
activities pertaining to the process, including technical decisions, definition of reference
framework, formulation of tender specifications and contracts, and the overseeing
and control of service provision.
36
3. Institutional models and payment for services
Table 1
Forms of urban cleaning service administration
Description
Administration
Direct municipal management
Urban cleaning activities run by a municipal
department or body.
Autonomous authority
Urban cleaning administration by a public company
specifically created for that purpose.
Outsourcing
The contracting of a private company to undertake
certain activities.
Concession
Employed when the public authority lacks sufficient
resources to finance the necessary investment in
the system.
Free market
Applied in the cases of large-scale generators
where regulations define maximum limits for
municipal collection, leaving the generator
responsible for contracting a collection company
at their own expense.
Consortium
An association of municipalities for common
measures and projects, especially in solid waste
final disposal.
A city’s urban, demographic and economic characteristics as well as the socio-cultural
particularities of its inhabitants must be considered in defining the form of
administration, while at the same time taking into account the following factors:
!
cost of service administration, management and supervision;
!
autonomy and flexibility in planning and decision-making;
!
autonomy in the application and reallocation of budgetary resources;
!
investment capacity for technological development, IT systems and quality control;
!
investment capacity for human resources and the generation of income and
employment;
!
responsiveness to social and political demands;
!
responsiveness to changing economic circumstances;
!
responsiveness to operational emergencies;
!
responsiveness to growth in demand for services.
As has already been said, direct administration of the entire urban cleaning system
is common in small cities. In such cases management is usually undertaken by a
municipal body or department that shares resources with other sectors of public
administration.
37
This type of administration that shares resources with other bodies of the municipality
usually has a relatively low cost in comparison with a body or institution exclusively
devoted to urban cleaning management. However, the other factors listed above are
difficult to achieve and the service tends to have a lower priority than other services
sharing the same resources and having a greater potential for political visibility.
In determining the form of urban cleaning services administration in
tourist cities seasonal fluctuations in demand for services has to be
particularly taken into consideration.
In cases where refuse collection and street cleaning services are outsourced by
contracting specialized companies, the municipality only undertakes the administration
of contracts and the monitoring of service quality and therefore the municipal
administrative nucleus can be small.
For their part, the companies charge the municipality enough to cover both operational
costs and capital expenditure, liberating the municipality of the need to invest resources
in the purchase of machines and equipment.
In such a model there can be problems when unforeseen eventualities arise, such as
ones relating to social and political demands, changing economic circumstances and
operational emergencies, as the predetermined form of remuneration established in
the contract may not cover them. It is therefore advisable that the municipality establishes
contract devices or alternative plans to deal with such eventualities.
A model that is worth highlighting is the one employed by the Rio de Janeiro City Urban
Cleaning Company (COMLURB), in the context of large Brazilian cities, and by the Public
Cleaning Companies of Cuenca, Ecuador, and Pereira, Colombia, in the context of
medium-sized cities in the Andean region. All of them are autonomous urban cleaning
companies and are therefore able to define their own budget allocations, establish
human resource policy and most importantly, determine plans, strategies and the logistics
of their operations. They can also outsource operational, management and
administrative services, and define the technical terms of contracts. These companies
can develop or subsidize research and technologies related to urban cleaning in general
as well as specific areas of it. The existence of such agencies exclusively devoted to
urban cleaning demonstrates the commitment of the municipality to keeping the city
clean and caring for the urban environment.
Whatever model is adopted, activities should always be regulated by
the public authority.
38
3. Institutional models and payment for services
In all cases, and whatever the administration modality, direct or autonomous, the
municipality has to harmoniously combine two elements:
3. 3
!
just and sufficient payment for services;
!
ensured collection of charges for urban cleaning.
Payment for services
The singularities of tax legislation in each Latin American and Caribbean country makes
it difficult to compile a complete generalized summary of the issue of payment for
urban cleaning services.
This chapter therefore concentrates on a basic outline of the subject, which in some
cases may need to be adapted to the particularities of each country’s legislation.
The term “tariff” refers to the price charged for a public service
provided in an optional form, that is to say that the tariff is
proportional to the amount and quality of the service used, which
must be well defined and specifically calculated.
The term “rate” on the other hand, refers to a tax on the availability of
a public service provided by the public authority, whether the taxpayer uses it or not. The value of the rate must reflect divisibility
amongst tax-payers in accordance with potential usage by each one.
In regard to the collection of payments for service provision, an urban cleaning system
can simply be divided into three components: domestic waste collection, street cleaning
and final disposal. In the case of domestic waste collection, for example, the Municipality
can charge residents a specific rate, usually called “Waste Collection Rate (WCR)”. In
cases of concession, the company responsible for providing such services may also
be responsible for collecting payments for them. Certain specific services where usage
can be measured and users are clearly identifiable can be priced and therefore be
charged for exclusively through a tariff.
Urban cleaning systems are financed by almost all of the population but not in a direct
way. Financial resources raised by the waste collection rate cannot be allocated
exclusively to the system due to municipal tax regulations. Similarly, a municipality cannot
charge residents of a street for the sweeping and cleaning services of that street in
particular as it is an indivisible service. It is therefore necessary that municipal policy
ensures a sufficiently large budget allocation to cover the cost of the system and
essential investment in it.
39
In some Latin American cities there is an incipient trend towards payment through
tariffs, i.e. where payment levels are related to the volume of waste generated. This is
being applied to particular geographical areas and follows the “pay as you throw”
principle.
There are few legal remedies for the problem of non payment, or delayed payment, of
rates or tariffs. Waste collection is not a service that can be suspended when bills are
not paid, as electricity or drinking water provision can be, because rubbish put in the
street by the non-payer has to be collected anyway for public health reasons.
In the absence of other available strategies, and even though it is a legally dubious
measure, in some cases an authority may resort to inscribing the property of the nonpayer in the municipal register of public debt. However this measure does not have
much punitive value as it represents only a long term threat to the non-payer in the
form of the eventual confiscation of his or her property.
There is no consensus about the most appropriate basis on which a municipal rate for
financing urban cleaning services should be calculated. There have been attempts to
relate the determination of this rate to the consumption of drinking water or electricity,
or to the frontage width of the plot, etc. In some countries only a reform of the tax
system would provide municipalities with the necessary instruments to reimburse them
in a socially just way for the urban cleaning services that they provide to citizens.
Once these issues are resolved, it has to be taken into account that financial resources
raised by cleaning and solid waste management rates become part of the Municipal
Treasury. There are no guarantees that they will be used in the urban cleaning sector,
this being dependent on the political will of the administration or public budget control
mechanisms. It should also be noted that the updating or correction of the rate depends
on authorization by the municipal council, which in general is not inclined to increase
the tax burden imposed on citizens, especially so in view of the socioeconomic
conditions of most Latin American and Caribbean populations.
It is therefore necessary to reverse the tendency to attribute a low priority to urban
cleaning services that results in them receiving fewer resources than are necessary. If
it is not possible to adequately finance the system, the quality of services deteriorates
and a vicious circle is established. The municipal solid waste management will be defective
due to insufficient resources and the population may not accept the payment of rates
because it is not receiving good quality service.
The municipality then has to choose one of the following options:
!
to face for a certain period the political cost involved in increasing taxes, if this is
necessary, until the situation balances itself with an improvement in the quality of
services provided;
40
3. Institutional models and payment for services
!
to subsidize the cost of the service during an initial period until service quality
reaches an adequate level, at which point the subsidy can be gradually reduced
as its value is gradually incorporated in the rate specifically charged to finance
the service.
In regard to investment, both for the purchase of equipment and the installation of
treatment and final disposal units, municipalities almost invariably need to resort to
sources of finance that do not always offer appropriate terms and involve prerequisites
that are not easy to adapt to.
A feasible solution for municipalities that do not have resources for investment is, as
has already been mentioned, outsourcing through contracts with private companies
that, with their own resources (labour and machinery), undertake collection, street
cleaning, treatment and final disposal services.
In such cases a concession can also be an appropriate alternative especially when the
necessary investment is higher and requires a more prolonged period to allow for a
return on it. Here a tariff is determined as the means by which the concession company
makes a return on its investment.
It is worth digressing to mention industrial waste management. In this case, a sustainable
balance must be established between generators and the private operators of centres
for treatment and final disposal. The investment needed for these units is very high
and the acquisition of licenses from environmental control bodies involves a long and
complicated process. However, when an industry is producing a certain product the
cost of an appropriate final disposal of waste generated in the production process
should be reflected in the sale price of that product.
Payment for urban cleaning systems is calculated by applying the following basic
equation:
Payments = Expenses
Expenses = Municipal Treasury resources + amount collected from WCR
+ amount collected from tariffs and various other incomes
Payments should cover the costs of the system which include
expenditure on labour, transport, maintenance, replacement of
vehicles and other equipment; backup, supervision and support
services; capital expenditure, research, technological development
and administration.
41
Irrespective of the management model adopted, Municipal Treasury resources plus the
money from tariffs should be equivalent to the budget for expenditure and capital
costs for all the operations involved in the cleaning of a city.
The payment for waste collection services to large generators (restaurants, hotels,
supermarkets, etc.) as well as for other services to which a tariff can be applied (i.e.
that can be measured) such as special collections, medical waste collection and the
removal of construction rubble or discarded items, can be charged by collecting
companies authorized by the municipality.
It should be emphasized that all operations not financed by adequate tariffs and an
efficient tax collection system, will have to be sustained by resources from the Municipal
Treasury, in which case the budget must allow for a specific allocation to the urban
cleaning sector, otherwise the Municipality would have to reallocate resources designated
for other areas.
It should be noted that an efficient way of reducing urban cleaning costs is to motivate
the population to decrease the amount of waste generated and implement specific
programs for the segregation of recyclable waste at source and its selective collection,
or create waste recycling subsidies.
The charging of a realistic and socially just rate that citizens can
afford and that effectively covers the cost of services and applies the
“he who can pays more” principle implies political measures that are
dependant on the will and determination of the mayor.
3.3.1
Guidelines for the calculation of a waste collection rate
For the system to be economically sustainable, the basic unit of the waste collection
rate (WCR) should be the quotient of the total budget for domestic solid waste collection
services and the number of households in the city.
The establishment of reliable administration and supervision mechanisms for all services
relating to urban cleaning is essential in order to correctly ascertain the real costs
involved in service provision and therefore the appropriate base for calculating the
amount of finance needed to operate the system in an efficient and sustainable way.
The basic WCR value can be adapted to the particularities of individual neighbourhoods
in the city, taking into consideration factors such as social stratum (with a view to
socially just pricing) and operational characteristics.
42
3. Institutional models and payment for services
Social stratum is determined on the basis of the average purchasing power of the
inhabitants of different zones of the city. In general a distributive criterion is applied,
so that higher income sectors subsidize services provided to the less well off.
Operational characteristics reflect the amount of labour and materials used in the
collection process depending on property usage (commercial, residential, etc.), location,
demographic density, topographic conditions, type of road surface, etc.
In recent years a more conservationist vision is increasingly influential in the
determination of pricing polices for urban cleaning. This approach involves a greater
community commitment to segregating waste at source (home, shop, market, etc.) in
order to facilitate collection, handling and particularly recycling. The promotion of this
model is important but depends on a wide motivational and educational campaign in
the community. The establishment of a charging mechanism based on the amount of
rubbish generated, so that those who generate more rubbish pay more, produces an
economic benefit for the population as a whole.
The budget also has to cover the costs of transfer, transport, treatment and final
disposal, as well as costs relating to administration, management, monitoring systems,
capital expenditure, education and technological development that are linked to
collection.
43
4
44
Legislation and environmental licenses
4. Legislation and environmental licenses
4.1
Introduction
Integrated municipal urban cleaning system management is based on the fundamental
conceptual premise of community participation and a systematic political exercise
involving all institutions linked to the pertinent spheres of government.
The community participates in this management in two ways:
!
contributing to the financing of services and monitoring them;
!
cooperating with cleaning by reducing the amount of waste; reusing, segregating,
classifying and recycling materials; appropriately preparing and storing waste for
collection, and by not throwing rubbish in the streets.
Community cooperation should be considered as the principal agent for transforming
the efficiency of services and consequently generating beneficial operational and
budgetary results.
Citizens can be encouraged to reduce the amount of waste that they produce in order
to diminish the costs of the operation. This approach could be called the principle of
service reliability and citizen cooperation for integrated solid waste management.
A combination of citizen cooperation and measures to increase the reliability of urban
cleaning services constitutes a powerful pairing that can solve the principal problems
relating to urban cleaning systems. Measures geared to guaranteeing good quality
operations and a well structured program of environmental education need legal
instruments that support them.
4.2
Legislation
The legislation required to set up an urban cleaning system falls into three general
categories:
!
the first, of a political and economic order, establishes the legal forms for
institutionalizing the administration of a system and the methods of payment and
charging for services;
!
the second, establishes operational codes, orientates, regulates and determines
procedures and the obligations of tax-payers and urban cleaning agents, and defines
administrative processes and punitive measures;
!
the third is the legal structure that regulates general environmental issues on a
national basis and in particular deals with licenses for the implementation of activities
that represent a risk to public health or the environment.
In Latin American and Caribbean countries there is wide ranging legislation in the form of
laws, decrees, ordinances, rulings and regulations that manifest an increasing concern
45
for environmental protection. In regard to urban cleaning initiatives mostly emanate from
municipal councils under their organic law and through local legal instruments.
For example, the Brazilian Federal Constitution determines that a municipality constitutes
a political entity, as prescribed by the 1st and 18th articles, which establish that the
Brazilian Federation comprises the Union, the states and the municipalities. Municipalities
can legislate, provide services, establish and collect municipal taxes and choose their
mayors and councillors.
As established by article 23, sub-sections VI and VII, municipalities are also responsible
for the protection of the environment, combating contamination and preserving forests,
fauna and flora. Article 30 sub-section I allows them to legislate for local matters in the
public interest and therefore to implement municipal environmental policy. Sub-section
II of the same article, authorizes them to supplement federal and state legislation where
appropriate, and sub-section VIII grants them exclusive authority to legislate on land
planning and land usage in their territory.
Article 225 of the Federal Constitution imposes on public authorities (Union, State and
Municipal) and the community a duty to defend and preserve the environment for
present and future generations thus establishing that a municipality has an obligation
of environmental protection. The municipality can therefore pass environmental
protection legislation and enforce it.
In most Latin American and Caribbean countries, a municipality can, under its organic
law, regulate the granting of licenses by the relevant municipal body for the exploitation
of water and mineral resources, and introduce other public authority instruments aimed
at protecting the environment, including the making of agreements to improve
environmental management.
Furthermore, when the governing plan for a city is formulated, in the section on
environmental policy an environmental management system can be established through
which environmental policy is implemented (Municipal Council for the Environment,
Environment Conservation Fund and Municipal Environment Department).
The environmental management system will include amongst its functions, the design
of environmental protection projects, either directly or through agreements; the
implementation of environmental impact assessment processes; the analysis of projects,
works or activities that actually or potentially produce environmental degradation; and
the requiring where necessary of environmental impact studies or environmental
recuperation guarantees prior to the granting of a license.
Taking into account the urban scale (determined by the number of inhabitants) and the
city’s socioeconomic and cultural circumstances, under their organic law municipalities
must decide on the best alternative for the institutionalization of the urban cleaning
system, the form of management, the charging of rates and tariffs and associations
with other bodies that can contribute or cooperate, irrespective of their institutional
status in the country.
Specifically, municipal urban cleaning regulations should serve as the spine of the city’s
urban cleaning system by establishing the essential principles that govern the conduct
of both municipal authority and citizens.
46
4. Legislation and environmental licenses
In recent times an innovative vision, known as ecosystem management, has come to
the fore in environmental assessment: the incorporation of the river basin concept in
the definition of the area of influence or impact of a project, which requires legal
instruments to cover the extrapolation of municipal responsibilities. This concept is
particularly significant in the case of defective management of solid waste dumps
located near the higher courses of rivers that form part of a water basin used for
water supplies to cities downstream.
Waste disposal in water courses represents an environmental risk that renders
populations vulnerable, especially in the event of natural disasters and particularly so
in the case of flooding.
4.3
Environmental licenses
It is necessary to establish a system for the granting of environmental licenses that
defines responsibilities, establishes criteria for environmental impact assessments and
identifies activities that require a prior environmental impact study, such as the
installation of a sanitary landfill.
Under the legislation of many Latin American countries it is the Environment Ministry
that is responsible for issuing licenses, as for example in Colombia, Chile, Paraguay,
Peru and Brazil.
In Brazil, a federal law establishes National Environmental Policy mechanisms, including
the granting of licenses and the revision of “actually” or “potentially” contaminating
activities. The same law requires that the construction, instalment, enlargement and
operation of establishments or the undertaking of activities that use environmental
resources and are considered as actually or potentially contaminating or degrading to
the environment, are dependent on the prior granting of a license by the competent
provincial body integrated in the National Environmental System, SISNAMA, without
prejudice to other required licenses.
Another legal instrument, echoing the text of the National Environmental Policy law,
establishes that the public authority, in exercise of its regulatory function, must grant
the respective licenses before the establishment of an installation and its operation
can begin. In many cases the renewal of a license is necessary to authorize the recommencement of an operation.
With a view to facilitating the granting of licences for new sanitary landfills and refuse
dump recuperation in small and medium-sized municipalities, specific legislation can be
passed that simplifies the processes involved in obtaining environmental licenses and
adapts them to the economic capacity of the Municipal Treasury.
47
4.4
Regulations applicable to solid waste
In other Latin American and Caribbean countries there are legal instruments applicable
to solid waste management that:
!
prohibit the entrance into the country of waste material for final disposal or
incineration;
!
establish a system for the granting of environmental licenses, regulate all related
aspects and establish criteria for determining which jurisdictions issue them;
!
create security zones around airports that restrict the establishment within them of
operations that attract birds;
!
define the responsibilities of and criteria for environmental impact assessments
and identify activities that require an environmental impact study;
!
establish criteria for the definition of requirements to obtain licences for works
involving sanitary issues;
!
determine appropriate procedures for the handling of damaged, contaminated,
uncategorized or abandoned material that is deemed to be a potential source of
environmental risk, until the relevant environmental body takes responsibility for it;
!
regulate environmentally sound initial disposal and management of used batteries,
including their collection, reuse, recycling, treatment and final disposal;
!
establish criteria for the granting of licences for industrial activities and for the
specific controls that existent waste, or the generation of waste, should be
subject to;
!
regulate the final disposal of discarded car, truck and bus batteries, tyres, used
oils, etc.
!
establish the definition and classification of solid waste from healthcare institutions,
ports, airports, railway stations and bus terminals and the minimum procedures for
its management;
!
determine a colour code system for different types of waste that must be used for
container identification and in educational campaigns on waste segregation;
!
define appropriate treatment and final disposal for medical waste.
Finally, there are aspects of solid waste management that can be subject to technical
regulations, such as:
!
the classification of solid waste by its potential risk to the environment and public
health, so that each type of waste can be appropriately handled and disposed of;
!
the definition of the minimum conditions required in the planning, establishment
and operation of non-hazardous waste landfills in order to appropriately protect
48
4. Legislation and environmental licenses
superficial and underground water resources, its operators and neighbouring
residents;
!
the definition of criteria for the planning, establishment and operation of hazardous
waste landfills;
!
the definition of criteria for the presentation of projects to establish municipal
solid waste controlled landfills;
!
the definition of criteria for the presentation of projects to establish municipal
solid waste sanitary landfills.
49
5
50
Solid waste: origin, definition
and characteristics
5. Solid waste: origin, definition and characteristics
5.1
Definition of rubbish and solid waste
The general public tends to think that “rubbish is everything that is not wanted any
more and is discarded; things that are useless, worn out and without any value.”
Technically, some regulatory entities define rubbish as: “the leftovers from human activity
that are considered useless, undesirable or disposable by the generators and that may be
solid or semi-solid” (substances or products with a humidity content of less than 85%).
The authors of studies on solid waste tend to use the terms “refuse” and “solid waste”
without distinction. In this manual solid waste and refuse comprises all solid or semisolid unwanted material that must be collected because the person that discards it
considers it to be of no use and gets rid of it by putting it in any receptacle intended
for that purpose.
It should be emphasized however, that in regard to rubbish the term “of no use” is
relative, as what is of no use for the person who discards it, can be transformed into
raw material for a new product or process. The concept of the reuse of waste therefore
prompts a reconsideration of the traditional concept of solid waste. Only material that
is not reusable by anybody can be truly considered to be rubbish.
5.2
Solid waste classification
Solid waste can be classified in different ways. The more usual classifications take
into account the waste’s potential risk for environmental contamination or its nature
and origin.
5.2.1
Potential environmental contamination risks
Solid waste can be classified as:
CLASS I
HAZARDOUS SOLID WASTE
Solid waste that is intrinsically inflammable, corrosive, reactive, toxic or pathogenic and
therefore represents a risk to public health in the form of increased mortality or
morbidity, or produces adverse environmental impacts when inappropriately handled
or disposed of.
CLASS II
NON-INERT SOLID WASTE
Combustible, biodegradable or soluble waste that can represent health or environmental
risks but does not fall within Class I, hazardous waste, or Class III, inert waste.
51
CLASS III
INERT SOLID WASTE
Waste with intrinsic characteristics that do not represent a risk to health or the
environment and that when sampled in a representative way in accordance with the
relevant norms and subjected to static or dynamic contact with distillate or deionized
water at room temperature (dissolution tests), does not have any of its dissolved
components in concentrations higher than those in drinking water patterns, except in
regard to aspect, colour, turbidity and taste.
5.2.2
Nature and origin
Origin is the principal element in categorizing solid waste. According to this criterion,
solid waste can be grouped in five categories:
!
Residential or domestic waste
!
Commercial waste
!
Street waste
!
Special domestic waste:
!
!
rubble
!
batteries
!
fluorescent tubes
!
tyres
Special origin waste:
!
industrial waste
!
radioactive waste
!
port, airport, railway station and bus terminal waste
!
agricultural waste
!
medical waste
RESIDENTIAL OR DOMESTIC WASTE
Waste generated by daily activities in houses, apartments, condominiums and other
types of residential building.
COMMERCIAL WASTE
Waste generated by commercial establishments, the characteristics of which depend
on the particular activities pursued by such establishments.
52
5. Solid waste: origin, definition and characteristics
In urban cleaning terms, “domestic waste” is made up of “residential waste” and “smallscale commercial waste” which, together with waste from street cleaning, represents
the majority of solid waste produced in cities.
Commercial waste and construction rubble can both be divided into two sub-categories:
“small generator” and “large generator”.
Municipal urban cleaning regulations can precisely define these two sub-groups. The
parameters could be:
Small commercial waste generators are establishments that generate up to 120
litres of waste per day.
Large commercial waste generators are establishments that generate more than
120 litres of waste per day.
Similarly, small generators of construction rubble are individuals or companies that
generate up to 1,000 kg or 50 bags of 30 litres per day, and large rubble generators are
those that generate a greater volume each day. Clearly these sub-categories cannot be
adopted without also establishing a minimum interval between any two collections of
rubble from the same generator and/or cumulative limits (by volume or weight) for
that generator over a certain period.
In general, the quantity of waste that defines the limit between small and large solid
waste generators should correspond to the average amount of solid waste generated
daily by a household with five residents.
In an urban cleaning system the definition of the sub-groups “small” and “large”
generators is important because a tariff can be applied to the collection of waste
produced by large generators, thus producing an additional source of income that
contributes to the economic viability of the system.
Alternatively it is important to identify large generators so that the waste generated by
them can be collected and transported by a private company authorized by the
municipality. This practice reduces by between 10% and 20% the cost of domestic
waste collection by the municipality.
STREET WASTE
Waste that is found in the streets produced by nature, such as leaves, branches,
dust, soil and sand, and waste discarded by people in a disorganized and improper
way, such as rubble, articles considered to be of no more use, paper, packaging
and food remains.
53
Street waste is directly related with the aesthetic appearance of a city and special
attention should therefore be paid to planning street cleaning services in tourist
cities.
SPECIAL DOMESTIC WASTE
This category consists of construction rubble, batteries, fluorescent tubes and tyres.
It is important to emphasize that construction rubble, also known as civil construction
waste, only comes under this category due to the large amounts in which it is generated
and the importance that its recovery and recycling is acquiring globally.
Rubble
The civil construction industry uses more natural resources and generates more waste
than any other. In many countries commonly used construction techniques for new
buildings involve a waste of materials. While in developed countries the average waste
produced in the construction of new buildings is less than 100kg per m², in Brazil, for
example, the corresponding figure is approximately 300kg per m².
Such material represents 50% of the total weight of municipal solid waste that is collected
in cities of the region with more than 500,000 inhabitants.
Civil construction waste is a mixture of inert materials such as concrete, mortar, wood,
plastic, cardboard, glass, metal, ceramics and soil.
Table 2
Average composition of construction
rubble in Brazil
Components
Mortar
63.0
Concrete and concrete blocks
29.0
Others
7.0
Organic waste
1.0
Total
Source: USP – University of Sao Paulo.
54
Percentage (%)
100.0
5. Solid waste: origin, definition and characteristics
Batteries
The basic principle of a battery is the conversion of chemical energy into electrical
energy using metals. They can have different shapes (cylindrical, rectangular, button
cell) and sizes and contain one or more of the following metals: lead (Pb), cadmium
(Cd), mercury (Hg), nickel (Ni), silver (Ag), lithium (Li), zinc (Zn), manganese (Mn) and their
compounds.
The substances in batteries that contain these metals are corrosive, reactive and toxic,
and are classified as “Class I - Hazardous Waste”.
Substances that contain cadmium, lead, mercury, silver and nickel have a negative
impact on the environment and particularly on human health. Other metals found in
batteries such as zinc, manganese and lithium can also cause environmental problems,
see table 3.
Table 3
Contaminant potential of chemical elements used in batteries
Element
Pb (lead)*
Effects on human health
!
abdominal pains (colic, spasm and rigidity)
!
kidney malfunction
!
anaemia, pulmonary problems
!
peripheral neuritis (paralysis)
!
encephalopathy (somnolence, manias, delirium,
convulsions and coma)
!
gingivitis, salivation, diarrhoea (with blood in the faeces)
!
abdominal pains (especially epigastria, vomiting,
metallic taste in the mouth)
Hg (mercury)
!
congestion, lack of appetite, indigestion
!
dermatitis and arterial hypertension
!
stomatitis (inflammation of the mouth mucosa), pharynx and
oesophagus ulceration, kidney and digestive tract lesions
!
insomnia, headaches, collapse, delirium, convulsions
!
brain and neurological lesions that produce psychological
problems
Cd (cadmium)*
!
digestive problems (nausea, vomiting, diarrhoea)
!
kidney malfunction
!
pulmonary problems
!
poisoning (when ingested)
!
pneumonitis (when inhaled)
!
cancer
* Even in small amounts
55
Table 3 (cont.)
Effects on human health
Element
Ag (silver)
Li (lithium)
Mn (manganese)
Zn (zinc)
!
digestive disturbances and mouth impregnation
!
argyria (chronic intoxication producing bluish skin colour)
!
death
!
inhalation – causes damage even with immediate attention
!
ingestion – minimal residual damage without treatment
!
neurological system malfunctions
!
neurological disturbances
!
stammering and insomnia
!
pulmonary disturbances
!
can produce residual damage without immediate treatment
!
contact with eyes – causes serious lesion even with
immediate attention
Ni (nickel)
!
cancer
!
dermatitis
!
general intoxication
Batteries made with non-toxic substances are now available on the market and these
can be disposed of without significant problems together with domestic refuse.
Fluorescent tubes
Fluorescent tubes, both the common cylindrical tubes and the compact fluorescent
bulbs, contain mercury steam and release mercury when they are broken, burned or
buried in sanitary landfills. Consequently they are classified as Class I hazardous
waste because mercury is a toxic substance that attacks the human nervous system
and when inhaled or ingested can provoke an enormous variety of physiological
problems.
When mercury is released into the environment and enters bodies of water
“bioaccumulation” takes place, a progressive increase in mercury concentrations in the
tissue of for example fish, which then become less healthy or even dangerous to
consume. When pregnant women eat such fish mercury is transferred to the foetus,
which is particularly sensitive to its toxicity. An accumulation of mercury can also occur
in the tissues of other wild species such as aquatic birds and animals.
56
5. Solid waste: origin, definition and characteristics
Tyres
The inappropriate disposal of tyres generates many environmental problems. If left in
the open air, tyres accumulate rainwater and serve as a breeding place for mosquitoes
thus fostering their proliferation. If they are disposed of in conventional landfills, they
will cause hollows in the mass of waste and increase landfill instability. If incinerated,
the rubber generates huge amounts of particles and toxic gases requiring a very efficient
and expensive gas treatment system. For all the above reasons, the disposal of tyres
has become a serious environmental problem that still does not have a truly effective
solution.
SPECIAL ORIGIN WASTE
Waste that due to its particular characteristics requires special handling, preparation,
storage, transport and final disposal. The main types of special origin waste are:
Industrial waste
Waste generated by industrial activity. Its composition varies greatly according to the
type of product that is being made. Consequently it is necessary to examine each
case individually in order to categorize it as Class I (hazardous), Class II (non-inert) or
Class III (inert).
Radioactive waste
Waste that emits radiation in excess of limits stipulated by environmental law.
Due to its specific nature and dangerous characteristics its handling, storage and
final disposal are the responsibility of national public bodies and are subject to
very rigorous controls. In Brazil, for example, the handling, storage and final disposal
of radioactive waste is undertaken by the National Nuclear Energy Commission
(CNEN, in Portuguese).
Port, airport, railway station and bus terminal waste
This category comprises waste generated in terminals as well as in boats, airplanes,
trains and buses. Waste from ports, airports and terminals results from consumption
by passengers in transit and its hazardous nature lies in the risk of transmission
of diseases already eradicated from a country when the incoming transports come
from an area where such diseases are endemic. Transmission can also take place
through potentially contaminated loads, such as animals, meat and plants.
57
Agricultural waste
This category mostly comprises the remains of containers and packaging impregnated
with dangerous pesticides and chemical fertilizers used in agriculture. The handling of
this type of waste should therefore follow the same practices and use the same
containers and process as those used for the handling of Class I industrial waste. Due
to a lack of controls and low fines for inappropriate handling of this type of waste, it
is often mixed with common waste and disposed of in municipal dumps or even worse,
thrown into bodies of water or is burnt in remote rural establishments thus generating
toxic gases.
Medical waste
This category consists of all the waste generated by healthcare institutions. The
classification of medical waste according to Brazilian standards (NBR 12.808 of the
Brazilian Association of Technical Standards, ABNT) is presented as an example in
table 4.
Table 4
Classification of medical waste
Type
Name
Characteristics
Class A – Infectious waste
58
A.1
Biological
Cultures, inoculae, a mix of micro organisms and an
inoculated culture medium coming from clinical or research laboratories, vaccine that is unusable or past
its use-by date, filters used to prevent inhalation of
gases in areas contaminated by infectious agents and
any refuse contaminated by the above materials.
A.2
Blood and blood
derivatives
Blood and blood derivatives past their use-by date,
HIV- positive blood, blood used for analysis, serum,
plasma and other derivatives.
A.3
Surgical, anatomical- Tissue, organs, foetuses, anatomical parts, blood and
pathological and
other organic liquids resulting from surgery and autopexudates
sies, and waste contaminated by the above materials.
A.4
Sharp and
puncturing
Needles, ampoules, pipettes, scalpel blades and glass.
A.5
Contaminated
animals
Skeletons or parts of animals that have been inoculated, exposed to pathogenic micro-organisms or are
carriers of infectious diseases, as well as waste that
has been in contact with them.
A.6
Patient care
Secretions and other organic liquids from patients,
as well as waste contaminated by them, including remains of food.
5. Solid waste: origin, definition and characteristics
Table 4 (cont.)
Type
Name
Characteristics
Class B – Special waste
B.1
Radioactive
waste
Radioactive material or material contaminated with
radionuclide, originating in clinical analysis laboratories, nuclear medicine services and radiotherapy.
B.2
Pharmaceutical
waste
Medicine that is past its use-by date, contaminated,
interdicted or of no further use.
B.3
Hazardous
chemical waste
Toxic, corrosive, inflammable, explosive, reactive
genotoxic or mutagenic waste.
Class C – Common waste
C
5.3
Waste that does not fall into classes A or B and that,
due to its similarity with domestic waste, does not
present any additional risk to public health.
Common waste
Characteristics of solid waste
Solid waste characteristics can vary according to the social, economic, cultural,
geographical and climatic factors that distinguish one community from another and
even one city from another.
Table 5 shows the variation in waste composition in some particular countries from
which it can be deduced that the percentage of organic matter tends to diminish in
more developed or industrialized countries, probably due to the large amount of semiprepared food available in the market.
Table 5
Gravimetric composition of waste in some countries (%)
Component
Brazil
Germany
The Netherlands
USA
65.00
61.20
50.30
35.60
Glass
3.00
10.40
14.50
8.20
Metal
4.00
3.80
6.70
8.70
Plastic
3.00
5.80
6.00
6.50
25.00
18.80
22.50
41.00
Organic matter
Paper
Waste can be analyzed according to its physical, chemical and biological characteristics.
5.3.1
Physical characteristics
Solid waste can be categorized according to the following physical characteristics: per
capita generation, gravimetric composition, apparent specific weight, humidity content
and compressibility.
59
PER CAPITA GENERATION
The relation between the amount of solid waste produced in a given region per day
and the number of inhabitants in that region. In the absence of precise data, per capita
generation can be estimated through table 6. However, the ideal is to carry out field
research and, based on statistical data, determine the daily waste generation per
inhabitant in relation to the population’s socioeconomic profile.
Tabla 6
Frequently used categories for determining per capita solid waste generation
Size of
the city
Urban population
(inhabitants)
Generation per capita
(kg/inhab/day)
Small
Up to 30,000
0.50
Medium-sized
from 30,000 a 500,000
from 0.50 a 0.80
Large
from 500,000 a 5,000,000
from 0.80 a 1.00
Megalopolis
over 5,000,000
over 1.00
Like table 6, figure 4 shows the correlation between the per capita generation of solid
waste and the population of cities. Although representative of averages determined
by several studies, these parameters should be considered with certain reservations
as particular local conditions may produce distortions in individual cases.
Figure 4 - Variation in per capita solid waste generation in relation to population size
60
5. Solid waste: origin, definition and characteristics
GRAVIMETRIC COMPOSITION
Gravimetric composition indicates the percentage of the total weight of an analyzed
waste sample that each component represents. The most commonly used categories
in the determination of the gravimetric composition of municipal solid waste can be
found in table 7.
However, many technicians tend to simplify the categories, for example considering
only paper/cardboard; plastic; glass; metal; organic matter and “other”. This type of
simplified category list, although useful for determining the dimensions of a composting
plant or other urban cleaning system installations, is not ideal in a precise economic
study for recycling or selective collection as, for example, the market for rigid plastics
is very different from the market for malleable plastic, as are the markets for ferrous
and non-ferrous metals.
Table 7
Most common components in gravimetric composition
Organic matter
Ferrous metals
Rubber
Paper
Non-ferrous metals
Leather
Cardboard
Aluminium
Cloths
Rigid plastic
Transparent glass
Bones
Malleable plastic
Coloured glass
Ceramics
PET
Wood
Fine aggregate
The decision about which components to include in a gravimetric composition study is
made on the basis of the type of study to be carried out and must involve great care
to avoid distortions.
APPARENT SPECIFIC WEIGHT
The apparent specific weight is the weight of loose waste in relation to the volume
that it freely occupies without any form of compacting and is expressed in kg/m³. It is
fundamental for determining the dimensions of necessary equipment and installations.
If precise data is not available, the following general specific weight values can be
used: 230 kg/m³ for domestic waste, 180 kg/m³ for medical waste and 1300 kg/m³ for
construction rubble.
However, it is necessary to carefully evaluate the specific situation before adopting
these values as variations exist in peoples customs and practices across the different
regions and countries of Latin America and the Caribbean.
61
HUMIDITY CONTENT
The humidity content is the amount of water contained by solid waste, measured as a
percentage of its weight. This parameter can vary by between 40% and 60 % depending
on the season and amounts of rainfall.
COMPRESSIBILITY
Compressibility is the degree of compacting that is possible, that is, the reduction of
volume that can be achieved in a mass of solid waste when it is compacted. Subjected
to a pressure of 4kg/cm², on average the volume of waste can be reduced to between
a third (1/3) and a quarter (1/4) of its original volume.
When the compacting pressure is withdrawn the mass of solid waste tends to expand
but it does not return to its original volume. This phenomenon, called expansion, must
be heeded when operating a landfill.
5.3.2
Chemical characteristics
CALORIFIC VALUE
This chemical characteristic indicates the potential heat generating capacity of a material
when incinerated. The average calorific value of domestic solid waste is approximately
3,000 kcal/kg.
POTENTIAL OF HYDROGEN (pH)
The potential of hydrogen indicates the acidity or alkalinity of waste which is generally
found to be between 5 and 7.
CHEMICAL COMPOSITION
The chemical composition indicates the amount of ashes, organic matter, carbon,
nitrogen, potassium, calcium, phosphorus, total mineral residue, soluble mineral residue
and fats contained in solid waste.
62
5. Solid waste: origin, definition and characteristics
CARBON/NITROGEN RATIO (C/N)
The Carbon/Nitrogen ratio indicates the degree of decomposition of solid waste organic
matter in treatment and final disposal processes. In general for domestic waste that
ratio is around 35/1.
5.3.3
Biological characteristics
Solid waste biological characteristics are determined by the microbial and pathogenic
agent populations and, together with the chemical characteristics, inform the selection
of appropriate treatment and final disposal methods.
Knowledge of the biological characteristics of solid waste has been extensively
utilized to develop odour inhibitors and substances used to delay or accelerate
the decomposition of organic matter, which are generally applied inside collection
vehicles to avoid or minimize problems caused to people along the routes of the
vehicles.
Similarly, final disposal and degraded site recuperation processes are being developed
based on the biological characteristics of waste.
5.4
Influence of solid waste characteristics
on urban cleaning system planning
Table 8 illustrates the influence of solid waste characteristics on urban cleaning system
planning and on the design of certain units that form part of the system.
Table 8
Influence of waste characteristics on urban cleaning
Importance
Characteristics
This data is fundamental for estimating the amount of
Per capita
generation
waste to be collected and disposed of. It is important
for
determining
vehicle
and
machine
capacity
requirements, tariffs charged for collection and the
necessary capacity of all the units that comprise the urban
cleaning system.
63
Table 8 (cont.)
Importance
Characteristics
Indicates the potential for the commercialization of recyGravimetric
composition
clable components, the use of organic matter to produce
compost and the application of other processes to the
solid waste.
Apparent
specific weight
Fundamental to correctly quantifying the required capacity
of the collection fleet, mobile and fixed containers and
other collecting equipment.
Directly influences the decomposition rate of matter in the
composting process. Directly influences the calorific value
and apparent specific weight of solid waste, thereby indi-
Humidity content
rectly influencing the determination of required incinerator
and composting plant capacity. Directly influences the calculation of percolate production and the required capacity
of the percolate collection system.
Very important for determining the required capacity of
Compressibility
collection vehicles, transfer stations with waste compaction facilities and fixed compaction containers.
Influences the determination of the required capacity of
Calorific value
installations for all thermo treatment processes (incineration, pyrolysis, etc.).
Indicates the degree of corrosiveness of collected waste
and is used to establish the type of protection against cor-
pH
rosion that it is necessary to apply to vehicles, machines
and metal containers and boxes. An important indicator in
the solid waste decomposition process in treatment and
final disposal units.
Important for determining the potential risk posed by solid
Chemical
composition
waste to human health and the environment. Contributes
to the determination of the most appropriate form of treatment for collected waste.
C/N ratio
Fundamental to the evaluation of composting process evolution and determining the quality of the compost produced.
Important in determining the sanitary risk posed by solid
Biological
characteristics
waste. Fundamental for the identification of odour inhibitors and substances to accelerate or delay the decomposition of organic matter in solid waste.
64
5. Solid waste: origin, definition and characteristics
5.5
Factors that influence solid waste characteristics
Clearly during rainy periods the humidity content in solid waste increases and during
the celebrations around the end of the year, and throughout the summer, the percentage
of aluminium (beer and cold drinks cans) in the waste increases. Consequently it is
necessary to take into account seasonal factors that can influence particularly the
physical characteristics of solid waste in order to avoid wrong conclusions in determining
the overall characteristics of waste.
Bank holidays and school holidays have an influence on the quantity of solid waste
generated in tourist cities.
Table 9 shows the principal factors that have a strong influence on solid waste
characteristics.
Table 9
Principal factors that influence solid waste characteristics
Factor
Effect
Climatic/seasonal
Rain
Autumn
Summer
!
increase in humidity content
!
increase in leaf content
!
increase in drinks container content (cans,
glass and rigid plastic bottles)
Special periods
Christmas /
!
cardboard, malleable plastic and metal)
New Year
School holidays
Other festivals
increase in packaging content (paper/
!
increase in organic matter content
!
population decrease in non-tourist areas
!
population increase in tourist areas
!
increase in drinks container content (cans,
glass and rigid plastic bottles)
Demographic
Urban population
size
!
the larger the urban population the greater the
per capita solid waste generation
65
Table 9 (cont.)
Factor
Effect
Socioeconomic
Purchasing power
!
the higher the purchasing power of the
population, the higher the proportion of
recyclable material and the lower the
proportion of organic matter
Purchasing power
!
greater consumption of luxury goods
immediately after payday (end and beginning
(monthly)
of month)
Purchasing power
!
(weekly)
Technological
greater consumption of luxury goods at
weekends
!
development
reduction in apparent specific weight of waste
due to the introduction of increasingly lighter
products
Commercial
!
increase in the amount of packaging
promotions
5.6
Processes for determining principal physical characteristics
Amongst the various types of solid waste characteristics the physical ones are the
most important to identify for proficient urban cleaning services management.
Not all municipalities can afford to set up laboratories to determine the chemical or
biological characteristics of solid waste, or have the financial resources to contract
private laboratories. The physical characteristics however can be easily determined
through processes undertaken in the field and only require: 200 litre metal containers,
a 150 kg capacity weighing machine, an oven and tools and implements commonly
used in urban cleaning.
The practical procedures presented below are employed to determine municipal
solid waste specific weight, gravimetric composition, humidity content and per capita
generation.
SAMPLE PREPARATION
!
collect initial samples with a volume of 2 to 3m³ from un-compacted solid waste
(loose refuse); the samples must be taken from different collection sectors to
obtain results that are as realistic as possible;
66
5. Solid waste: origin, definition and characteristics
!
deposit the initial samples on a sheet of canvas extended on flat land and mix them
until obtaining one homogeneous pile, using shovels and hoes to rip plastic bags
and break cardboard boxes, crates and other materials used to package the waste;
!
divide the pile of homogenized waste into four equal parts and select two of them
(always opposite quarters, not adjacent ones). Mix these two parts homogenizing
the content (the remaining two quarters should be sent for final disposal in the landfill);
!
repeat the previous procedure until the volume of each of the quarters is just
over 1m³:
!
separate one quarter at random and use it to completely fill five previously weighed
200 litre metal containers;
!
after filling the containers, break up the rest of the selected quarter with machetes
in a place that is protected from the elements (sun, rain, wind or high temperature);
fill a two litre container with the broken up material and close the container as
hermetically as possible.
APPARENT SPECIFIC WEIGHT
DETERMINATION
!
weigh each of the filled 200 litre containers and determine the net weight of the
waste subtracting the weight of the container;
!
add up the net weights;
!
determine the apparent specific weight (expressed in kg/m³) by dividing the total
net weight of the waste in the five containers (in kg) by the total volume of the 5
containers, i.e. 1m³.
GRAVIMETRIC COMPOSITION
DETERMINATION
!
define the list of components to identify depending on the objectives;
!
spread the contents of one of the containers on a canvas sheet extended on
flat land;
!
separate the waste according to the defined list of components;
!
classify as “other” all material found that does not fall into any of the categories on
the predefined list of components;
!
weigh each component separately;
!
divide the total weight of the sample by the weight of each component and calculate
the percentage of each component in relation to the whole in order to determine
the gravimetric composition.
67
HUMIDITY CONTENT
DETERMINATION
!
weigh the two litre sample;
!
put the sample in an oven at 105ºC for 24 hours or at 75º C for 48 hours;
!
weigh the dry material repeatedly until the weight remains constant;
!
subtract the dry material weight from the humid sample weight thus determining the
percentage of humidity.
CALCULATION OF
PER CAPITA GENERATION
The per capita generation of solid waste can be determined by means of field
studies on households pre-selected on the basis of appropriate statistical data so
that they are representative of the overall socioeconomic profile of the population,
or by means of procedures undertaken at the final disposal site that produce
relevant data.
The following is a simplified calculation methodology for use in cities without a
weighbridge to weigh solid waste on arrival at the final disposal site.
!
measure the volume of waste taken to the landfill during one working week;
!
convert the total volume (in m³) of waste that has arrived at the landfill into total
weight (in kg), using the specific weight value determined by applying the technique
described in a previous section;
!
estimate the percentage of the population served by the collection service;
!
based on the above percentage and the total number of inhabitants in the city
calculate the number of inhabitants served by the collection service;
!
calculate the per capita generation rate by dividing the total weight of waste (in kg)
by the number of inhabitants served and then dividing this result by seven to obtain
the daily rate.
The following observations are significant:
!
sample collection and the measurement of waste being taken to a landfill must
never be undertaken on a Sunday or Monday as, due to collection patterns, these
are atypical days for the purposes of determining waste generation;
68
5. Solid waste: origin, definition and characteristics
!
in tourist cities samples should never be taken during school holidays or bank
holidays, unless a determination of seasonal influence on the city’s waste generation
is required;
!
never measure humidity content on a rainy day;
!
where possible measurements should always be taken between the 10th and the
20th of a month to avoid distortions nearer the end of a month.
69
6
70
Solid waste quantity projections
6. Solid waste quantity projections
For an accurate solid waste generation projection, it is necessary to have demographic
data on the resident and seasonal populations, especially in tourist cities where tourists
can sometimes generate more solid waste than permanent residents.
It is important to have data on seasonal fluctuations in population numbers and to
take this into account when making projections for solid waste generation in tourist
cities.
A careful analysis should be made of up to date demographic data in order to make
reliable population projections (see table 10) and calculate solid waste production
over time.
The following example shows procedures to be followed.
Let us suppose that a projection is required for an urban cleaning system in a nontourist city with a current urban population of 50,000 that is growing at an annual
rate of 3% and where the per capita waste generation has been measured as 530g/
inhab/day.
With a projection horizon of 20 years population values would be as in table 10:
Table 10
Demographic projection
Year
Urban population
(inhabitants)
Year
Urban population
(inhabitants)
Current
50,000
11
69,211
1
51,500
12
71,287
2
53,045
13
73,426
3
54,636
14
75,629
4
56,275
15
77,898
5
57,963
16
80,235
6
59,702
17
82,642
7
61,493
18
85,121
8
63,338
19
87,675
9
65,238
20
90,305
10
67,195
It is known that the greater the economic development of a city (in general related
to population size), the larger the per capita solid waste generation. Therefore, in
71
such a case the evolution of the per capita production would be estimated as in
table 11:
Table 11
Evolution of per capita solid waste generation
Period
Per capita (g/inhab/day)
Year 1 to 7
530
Year 8 to 14
540
Year 15 to 21
550
Thus the projected amount of solid waste produced daily over 20 years is as in
table 12:
Table 12
Projected amount of solid waste generation
72
Year
Demographic projection
(inhabitants)
Current
50,000
0.53
26.5
1
51,500
0.53
27.3
2
53,045
0.53
28.1
3
54,636
0.53
29.0
4
56,275
0.53
29.8
5
57,963
0.53
30.7
6
59,702
0.53
31.6
7
61,493
0.54
33.2
8
63,338
0.54
34.2
9
65,238
0.54
35.2
10
67,195
0.54
36.3
11
69,211
0.54
37.4
12
71,287
0.54
38.5
13
73,426
0.54
39.7
14
75,629
0.55
41.6
15
77,898
0.55
42.8
16
80,235
0.55
44.1
17
82,642
0.55
45.5
18
85,121
0.55
46.8
19
87,675
0.55
48.2
20
90,305
0.55
49.7
Per capita
(g/inhab./day)
Amount of
waste (t)
6. Solid waste quantity projections
When an Integrated Solid Waste Management Plan is formulated, it is common to consider
a five year projection horizon for planning waste collection and the cleaning of streets
and other public spaces. A five year horizon is used because changes in a city’s
urbanization are significant over a period of time greater than that, especially in mediumsized and large cities in Latin America and the Caribbean. At the end of the five years
an assessment of the situation is made and if necessary planning is updated.
For projections relating to solid waste treatment and final disposal a 15 year term is
more common.
73
7
74
Solid waste preparation and storage
7. Solid waste preparation and storage
7.1
Concept
Pre-collection solid waste preparation and storage should be done in an appropriately
sanitary way taking into account the type and quantity of waste
7.2
The importance of appropriate preparation and storage
The quality of solid waste collection and transportation operations depends on an
appropriate preparation and storage of waste and its presence in the place, on the day
and at the time established by the urban cleaning body responsible for collection.
Citizens participation in this operation is therefore of great importance.
Appropriate preparation and storage is important for:
!
avoiding accidents;
!
avoiding vector proliferation;
!
minimizing visual and odour impacts;
!
reducing waste heterogeneity (in the case of selective collection);
!
facilitating collection.
In many cities open air domestic waste accumulation points appear spontaneously causing
scattered refuse in the streets, damage to the environment and a risk to public health.
Figure 5 – Open air solid waste accumulation point
Incorrectly prepared and stored solid waste attracts animals.
In urban zones of low quality dwellings and low demographic density there are generally
more animals, such as dogs, horses and pigs, that roam freely in the streets and
frequently tear rubbish bags and knock down containers to access the remains of
food, which results in waste being scattered over a large area. In addition such domestic
waste attracts rats, mice, flies, cockroaches and other disease vectors that feed and
breed in the refuse.
75
To limit damage caused by the activities of such animals it is recommended that:
!
the municipality implements regular operations to remove animals that are free in
the streets;
!
refuse collection is more frequent and regular in such zones;
!
inhabitants of such zones are instructed to put refuse out in the street at a time as
close as possible to the collection time;
!
a more appropriate type of container is provided for the solid waste, with special
anchoring devices that enhance their stability;
!
the relevant public body takes action to contain the proliferation of rats and mice.
In Latin American and Caribbean cities diverse containers are used for putting out and
storing domestic waste for collection:
!
metal or plastic bins;
!
plastic bags, supermarket type or specifically for refuse;
!
wood or cardboard boxes;
!
used oil and fuel drums, sometimes cut in half;
!
large metal or plastic containers, stationary or on wheels.
There are also creative initiatives for storing this type of waste. An example can be
found in cities in the north and northeast of Brazil, where alternative containers are
skilfully made with old tyres. This is a way of using discarded tyres but the containers
are heavy and not very practical, however they are acceptable in the context of the
socioeconomic conditions that prevail for most inhabitants there.
7.3
Characteristics of pre-collection storage containers
The choice of container type should be based on:
!
refuse characteristics;
!
quantity of refuse generated;
!
frequency of collection;
!
type of building;
!
price of container.
Receptacles for domestic waste pre-collection storage should have the following
characteristics:
!
a maximum loaded weight of 30 kg if the collection is manual;
Larger containers should be standardized so that they can be handled by mechanical
devices incorporated in the collector vehicles in order to reduce manual labour.
76
7. Solid waste preparation and storage
!
devices that facilitate its movement between its place in the building and the place
of collection;
!
closable in order to avoid waste spillage or exposure;
Flexible packaging (plastic bags) should be closable. Rigid and semi-rigid receptacles
(plastic and metal bins, containers) should have lids and be stable enough that they are
not easily knocked over.
!
safe in that injury is not caused to users or collectors by sharp edged or pointed
waste, including when separately packaged;
!
economical and affordable for the general public;
!
not producing excessive noise when handled;
!
easy to empty without leaving waste at the bottom.
From a planning perspective another characteristic has to be taken into account:
whether the receptacles are returnable or non-returnable.
In the latter case collection will be more efficient, after collection there will be no
receptacles left on the street and residents will not need to clean receptacles.
For these reasons, it can be concluded that plastic bags are the most convenient
receptacles for storing domestic waste prior to manual collection because:
!
they are easy to close by tying;
!
they are light, non-returnable (so collection is more efficient) and allow for silent
collection, an important factor particularly for nocturnal collections;
!
their price is affordable and they can be standardized.
In Latin American and Caribbean cities where the income level of most inhabitants is
low, the use of supermarket plastic bags (used for transporting purchased products to
the home) can be acceptable for the pre-collection storage of domestic waste as they
do not involve any extra cost.
From an environmental perspective there are usually reservations about the use of
plastic bags for domestic waste storage, especially in connection with waste incineration
processes. However, polythene bags do not contaminate the atmosphere when
appropriately incinerated. Another issue is that most plastic bags are non-biodegradable,
but as the use of sanitary landfills is a practically definitive waste disposal method,
there are not many objections to their use.
77
In regard to the safe handling of plastic bags containing waste, appropriate procedures
to reduce the risk of injury to collectors must always be observed, it being fundamental
for example, that they wear appropriate protection gloves. Plastic bags with a capacity
of more than 100 litres are not safe as collectors tend to hold them against their
bodies while carrying them to the truck and pieces of glass and other sharp objects in
the waste can injure them.
For multi-family housings (apartment blocks) and office blocks standardized wheelie
bins with lids are more appropriate as they allow for semi-automatic collection, which
is more efficient and safer. These containers are easy to handle as they have wheels,
are light, relatively silent, and economical due to their durability (especially if not exposed
permanently to sunlight) and have a pleasing appearance. There are wheelie bins of
120, 240 and 360 litre capacity on the market.
Figure 6 – Standardized wheelie bins
7.4
Domestic waste pre-collection preparation and storage
The most appropriate containers for pre-collection domestic waste storage are plastic
bags, wheelie bins and metal containers.
78
7. Solid waste preparation and storage
Plastic bags
Waste can be stored in non-returnable plastic bags to be collected by collection vehicles.
Such plastic bags should have the following characteristics:
!
resistance so that they do not break when handled;
!
a capacity of 20, 30, 50 or 100 litres;
!
a tape to close the top;
!
a colour standardized by the relevant body
In general these characteristics are regulated by technical standards.
Plastic wheelie bins
These are containers made of high density polyethylene (HDPE) with a capacity of 120,
240 or 360 litres (two wheeled bins) and 760 or 1,100 litres (four wheeled containers),
comprising a body, a lid and wheels. They are made of partly recycled material plus
additives to protect them from the action of ultraviolet rays.
They are used for the storage and transport of domestic waste, but can also be used
for certain public waste (for example when they are used to store the waste from
street sweeping).
Domestic waste produced by large generators – the
collection and transport of which should be undertaken
if possible by private companies authorized by the
municipality – can be stored in containers similar to the
one in figure 7, different only in their colour from those
for residential waste.
Figure 7 – Plastic wheelie bin
Metal containers
These receptacles, with a capacity that ranges
between 750 and 1,500 litres, generally have
four small wheels and can be emptied by
means of tipping devices installed in
compaction trucks.
Figure 8 – Metal container
79
Figure 9 – Mechanized metal container tipping
7.5
Pre-collection storage of street waste
Rubbish bins
There are several types of container that can be installed in the street for passers-by
to deposit rubbish, in order to maintain the city in a hygienic and clean condition.
For many years this type of container was metallic and was of a shape and colour
determined by municipal administrations. The high costs of the production, maintenance
and replacement of these metal bins were an obstacle to them being more widely
used.
Currently plastic rubbish bins are increasingly used as they are lighter, more durable,
easier to install and cheaper.
Such rubbish bins have a capacity of 50 litres and consist of a body in which rubbish is
deposited, a lid and a metal tray to stub out cigarettes before throwing them into the
bin. They are made of partly recycled material plus additives to protect them from the
action of ultraviolet rays.
These containers should be installed in parks, squares, public gardens, streets, avenues
and other public spaces that people pass through.
This type of bin can be used for other purposes. For example, a growing environmental
awareness in society is resulting in the separation of used batteries that, due to an
ever intensifying use of portable electrical and electronic gadgets, are becoming
increasingly numerous. In this context the use of plastic rubbish bins with a 50 litre
capacity, a standardized colour and a special hole in the front part of the lid represents
a good option for storing discarded batteries.
80
7. Solid waste preparation and storage
Figure 10 – Rubbish bin
Figure 11 – Battery bin
Plastic bags
Plastic bags similar to those used for residential waste can be used for the pre-collection
storage of public waste.
The difference is that bags for public waste, particularly that collected by sweeping,
can be bigger.
Construction rubble requires the use of thicker plastic bags with less volumetric capacity
due to the higher specific weight of the material to be stored.
Wheelie bins /stationary containers
As with plastic bags, plastic containers for public waste are exactly like those used for
storing residential waste. However metal containers are different.
Metal containers used for public waste pre-collection storage are stationary receptacles
generally with a volumetric capacity of 5 or 7 m³ that can be emptied by compactor
trucks (depending on the nature of the waste) or by dumpster carrier trucks equipped
with a multifunctional crane to load and unload the containers.
This type of container is interchangeable and the vehicle that collects a full container
brings an empty one to replace it. This system is also known as “brooks” or “dumpster”.
Figure 12 - – Dumpster carrier truck with multifunction crane transporting stationary container
81
7.6
Pre-collection storage of waste in low
demographic density and low-income areas
In informal settlement dwellings and low-income housing estate households there is
usually little space for storing waste. Consequently as waste is produced it is taken
out of the houses and put on the street, which results in the above mentioned
environmental and sanitary problems.
In such circumstances standardized plastic containers (with wheels and lid) can be
located at previously determined points with as frequent collections as possible.
If it is not possible to provide plastic containers, one alternative is to provide brooks
type dumpsters. However experience demonstrates that this type of container does
not produce satisfactory results as, amongst other problems, waste becomes scattered
around it, animals forage in it, there can be fires due to acts of vandalism and a bad
odour is produced.
Such problems result from a series of factors, one of which is the design of the
containers that in general do not have a lid, and when they do have one, users tend to
ignore it. For all the above reasons, when this type of storage is adopted containers
must be changed at appropriately frequent and rigorously observed intervals in order
to maintain the cleanliness of the area, awareness raising campaigns should be instigated
in the community and an efficient supervision system should be set up.
Figure 13 – Brooks dumpster outside a low income community settlement
Compaction containers represent a more appropriate solution than brooks dumpsters
for pre-collection storage of domestic solid waste in such special areas. They are
stationary closed metal containers with an incorporated waste compaction device,
and are handled by special vehicles. Their use depends on the amount of waste
generated by a community and the technical, operational and economic capacities of
the municipality.
82
7. Solid waste preparation and storage
Figure 14 – Compaction container system
It is advisable to establish a team of workers to operate a system for maintaining clean
and hygienic conditions in the most problematic poor communities.
In some cities, Rio de Janeiro for example, contracts are established with residents
associations in low income communities whereby they undertake the operation of
domestic waste collection and cleaning services for internal streets. One of the
conditions of this type of contract is that local labour is employed so that local jobs
are generated and the community’s awareness of these issues increases as it becomes
directly responsible for the cleaning of the settlement. The body responsible for
urban cleaning pays for the services undertaken, provides technical support and
supervises the quality of the operation. The associations hire their own employees
and are responsible for the management of the work. Satisfactory results from this
type of program have led to its implementation in almost all of Rio de Janeiro’s informal
settlements.
7.7
Pre-collection storage of waste produced by large generators
Where a specific regulation specifies that commercial and industrial establishments
generating more than 120 litres of solid waste per day are categorized as “large generators”,
containers for the pre-collection storage of such waste should be standardized.
The limit of 120 litres was established to correspond with the capacity of the smallest
plastic container with lid and wheels that is available on the market.
It is practical for containers used by large generators to be different in colour and size
from those used for normal collections in order to facilitate supervision (for example,
blue containers for large generators and orange containers for normal collections).
For collections from large generators and public establishments, in general two main
types of large container with a capacity of more than 360 litres are used:
83
!
metal or plastic (high density polyethylene) containers on wheels that are taken to
collection vehicles and mechanically emptied into them. In general these containers
have a capacity of 760, 1,150 or 1,500 litres.
!
stationary containers without wheels, generally metal, that are interchangeable or
are emptied into collection trucks. Containers of up to 5m³ are emptied into collection
trucks by means of steel cables powered by hydraulic devices.
Interchangeable containers are moved by dumpster carrier trucks with multifunctional
cranes or by roll-on /roll-off type trucks. These metal containers have a capacity of 3
to 30 m³. The very large containers (20 to 30 m³) are moved by roll-on/roll-off truck
equipment either with steel cables pulled by a winch or by hydraulic cylinders, and can
be equipped with electric devices for compaction, in which cases they are informally
referred to as “compactainers”.
Figure 15 – Double dumpster carrier truck
with interchangeable containers
Figure 16 Roll-on /roll-off truck
7.8
Special domestic waste pre-collection storage
Construction rubble
Due to its high apparent specific weight, construction rubble is normally stored in
stationary metal containers of 4 or 5m³, similar to those used for storing public waste.
Due to the large volumes of rubble, and therefore the size of containers needed to
store it, a significant problem is caused for the circulation of passers-by and vehicles
as well as for parking vehicles. In addition construction rubble uses a lot of space in
sanitary landfills, space that could be used to deposit non-recyclable types of waste.
Within the concept of sustainable development established by Agenda 21, the
reduction of waste and the reuse of it and its by-products are fundamental to the
new approaches that society must adopt. The biggest challenges presented by
construction rubble are:
84
7. Solid waste preparation and storage
!
to reduce the amount of rubble generated thus reducing the use of limited space
available for disposal;
!
to reuse generated rubble in the productive cycle thus reducing the consumption
of energy and natural resources.
Batteries
Partially discharged batteries must be stored in such a way that their electrodes do not
come into contact with the electrodes of other batteries or with metal objects such
as the internal sides of a metal drum. Partially discharged nickel-cadmium batteries must
be individually pre-wrapped in plastic bags.
Containers with stored batteries must be sealed to avoid the release of hydrogen,
which is explosive in contact with the air, and must be kept on platforms or pallets in
order to keep them dry. Storage containers should be located in places with good
ventilation and protection from the elements. The large numbers and variety of devices
that use batteries, together with their small size and the general public’s lack of
knowledge about the dangers that they pose, have resulted in them often ending up
together with the general domestic waste in sanitary landfills where they contaminate
the environment.
Due to their toxicity and the difficulties involved in stopping them being discarded in
domestic refuse, responsibility for the storage, collection, transport and final disposal
of batteries should be taken on by producers, importers, commercial outlets and
technical assistance networks.
Any legal measures implemented for the regulation of such a system must set a specific
timeframe for these stakeholders to establish operational mechanisms for the
collection, transport and storage of discarded batteries.
Legislation should also establish a timeframe within which producers and importers of
batteries must implement reuse, recycling, treatment and final disposal systems.
Fluorescent tubes
Fluorescent tubes also require specific legislation to regulate the way in which they
are discarded, stored and handled, and their treatment and final disposal. Such legislation
should reflect the “polluter pays” principle.
85
Procedures for handling fluorescent tubes that contain mercury must respect the
following requirements:
!
intact tubes should be stored in boxes, if possible plastic ones, in a reserved area
to avoid them being broken;
!
all boxes should be labelled;
!
tubes should not be broken or physically modified;
!
once a sufficient number of tubes has been accumulated they should be sent for
recycling, accompanied by the following information:
!
!
source (name and address of company or institution), details of the
transport company and the recycling company;
!
number of tubes sent;
!
date dispatched;
!
a record of these invoices must be kept for at least three years;
if a tube breaks, the pieces of glass must be removed and the area must be
washed;
!
broken tubes should be stored in sealed containers and labelled in the following
way: “Broken fluorescent tubes containing mercury”.
Tyres
Due to problems associated with the inappropriate disposal of tyres, and following
the example of the system for dealing with batteries, producers and importers of
tyres should be obliged to collect and dispose of discarded tyres in an environmentally
sound way.
One of the principal problems with the storage of tyres for collection or recycling is
that they accumulate water when left out in the open and thus facilitate the proliferation
of disease vectors.
Tyre storage should respect the following guidelines:
!
tyres should not be accumulated but should be sent for disposal at the time that
they are discarded;
!
if it is necessary to keep them, this should be done in covered areas protected
from the elements;
!
they should never be burned.
Discarded tyres have been used as fuel in furnaces for the production of cement and
also to produce asphalt.
86
7. Solid waste preparation and storage
7.9
Special origin waste pre-collection storage
Industrial waste
Industrial waste is usually stored in:
!
200 litre metal drums for non-corrosive solid waste;
!
200 or 300 litre plastic drums for corrosive solid waste or semi-solid waste in general;
!
flexible containers, i.e. bags, usually of woven polypropylene, with a large storage
capacity almost always of more than 1m³;
!
standardized plastic containers of 120, 240, 360, 750, 1,100 and 1,600 litres for
waste that allows for the use of returnable containers;
!
medium-sized cardboard boxes of up to 50 litre capacity for waste to be incinerated.
Radioactive waste
The handling and storing of radioactive waste must comply with the stipulations of the
national body responsible for the control and supervision of this type of waste, which
include the following requirements:
!
personnel handling this type of waste must use the obligatory minimum individual
protection equipment;
!
containers must be radiation proof (lead, concrete, etc.).
Port and airport waste
From a sanitary perspective ports and airports are places where not only people and
goods disembark but also diseases. It is therefore necessary to establish permanent
sanitary vigilance and handle waste in a particularly hygienic manner.
In normal conditions, handling and storage of waste follows the same procedures and
uses the same receptacles as those for domestic waste. However in cases of quarantine
alert, or other situations of risk identified by the body responsible for sanitary vigilance,
special methods must be applied to the handling of personal waste and goods coming
from countries with epidemics.
Medical waste
The handling of medical waste (see table 4) must follow specific regulations that stipulate
procedures for waste segregation at source, storage and management.
87
The principal procedure is the segregation at source of infectious and common waste.
Infectious waste represents between 10 and 15 % of all waste but carries a high
contamination risk while common waste does not require any special treatment.
A lack of care when handling infectious waste is the principal cause of infections in
hospitals. An example that illustrates this is the case of municipal hospitals in Rio de
Janeiro where, after the introduction of clear infectious waste segregation procedures,
the rate of hospitalization due to such infections diminished by 80%.
Pre-collection storage of common waste follows the same procedures as for domestic
waste.
Infectious waste must in general be put in well identified strong impermeable plastic
bags at the moment of its generation.
Special waste should be stored in receptacles that guarantee its physical integrity.
They should be strong, rigid plastic containers with hermetic lids and a clear identification
of the type of waste that they contain.
Puncturing and sharp waste (needles, glass, etc.) must be separately discarded at
source in rigid containers with hermetic lids and a clear identification of the type of
waste that they contain.
Plastic bags should comply with established colour code specifications. In Brazil the
criteria are the following:
!
transparent – common waste, recyclable
!
opaque colours – common waste, non-recyclable
!
cream – infectious or special waste (except radioactive waste)
Figure 17 – Plastic bags for medical waste
88
7. Solid waste preparation and storage
Subsequently the plastic bags must be placed in containers that can be easily moved to
a temporary storage facility. These containers must be white for infectious waste and
any other colour for common waste.
Figure 18 – Infectious waste containers
Temporary storage facilities must have tiled floors and walls and rounded corners to
facilitate the washing of floors and walls.
Figure 19 – Temporary storage facility for infectious waste
containers
Personnel handling infectious waste (except radioactive and hazardous chemical waste,
which are not the responsibility of urban cleaning systems) should use the following
individual protection equipment (IPE):
!
plastic apron;
!
plastic gloves;
!
PVC boots (for floor and wall washing) or closed shoes;
!
goggles;
!
mask.
89
8
90
Solid waste collection and transport
8. Solid waste collection and transport
8.1
Domestic waste collection and transport
8.1.1
Concept
Collection is the removal of waste stored by the generator for dispatch by appropriate
transport to a transfer station, treatment unit or final disposal site.
The collection and transportation of domestic waste generated in households and
small-sized public, commercial or service establishments is generally undertaken by
the municipal body responsible for urban cleaning. Municipalities may provide these
services through their own resources, concessions to companies, outsourcing to
companies, or mixed systems such as rented vehicles and municipal labour.
It is recommended that solid waste from large generators (establishments that produce
more than 120 litres of waste a day) is collected by private companies, registered and
authorized by the municipality, without any cost to the public system.
Hotels and restaurants are examples of large solid waste generators in tourist cities.
Common domestic waste collection can be defined as the collection of refuse produced
in residential, public and commercial buildings, provided that the latter do not represent
large generators.
8.1.2
Collection regularity
Domestic waste collection services to each building should be regular, always on the
same days of the week and at the same times. When services are regular, citizens will
become accustomed to taking waste containers or bags out to the pavement in front
of their building a short time before the collection vehicle passes.
Consequently domestic waste is not left exposed in the street for more time than is
necessary, thus avoiding the presence of unsightly waste in the street and its scattering
by animals or people.
In tourist cities special attention should be paid to the amount of time that waste
remains in the street, due to the importance of aesthetics, unpleasant odour emissions
and the danger of attracting disease vectors and animals.
Regular collection is therefore one of the principal requirements for a good quality
service.
91
In cities that have the means to weigh collected waste, the regularity of collections can
be mathematically verified by comparing the weight of waste over two or three
consecutive weeks. The weight of waste collected on the same day of each week (for
example the weight of the waste collected on a Monday compared with that of the
waste collected the following Monday) should not vary by more than 10%. Similarly, the
distance travelled by collection vehicles should be more or less constant on the same
day of different weeks as the itinerary of each particular day of the week is always the
same (with the same number of journeys to the waste destination point).
Collection irregularities are clearly indicated by accumulations of waste in the streets
and by the amounts of complaints received. The ideal for a domestic solid waste
collection system is therefore to establish fixed collection times and inform the entire
community of them through individual communications to the responsible person in
each building and even the posting of notices in the streets. The community will come
to trust the reliability of the collection service and will then cooperate by not discarding
waste in inappropriate places, by storing waste for collection in appropriate receptacles
and by putting it out in the appropriate place on the day and at the time stipulated, all
of which will contribute to increased environmental hygiene and public health, and the
cleanliness and improved appearance of the street.
8.1.3
Collection frequency
For climatic reasons, in most Latin American and Caribbean cities the interval between
domestic waste generation and its final disposal should be of no more than one week
in order to avoid bad odours and the proliferation of flies, rodents and other animals
attracted by the waste.
This situation is exacerbated in cities that use transfer stations (see chapter 9) as
waste is stored there for one or two days before being transported to the landfill
where it is finally covered with earth at the end of the day it arrives. If domestic waste
collection frequency is three times a week, the waste produced for example on a
Saturday may not be collected until the following Tuesday (three days later). If it is then
stored in the transfer station for two days and one more day is required for its burial
in the landfill, the total number of days between generation and final disposal can be
as many as six. Consequently, the minimum collection frequency recommended for
warm weather countries is three times a week.
Twice weekly collections, which are very common in suburban areas of Latin American
and Caribbean cities, should therefore be avoided. Budgetary restrictions represent
one of the main obstacles that municipal administrations face in their attempts to provide
sufficiently frequent services.
The capacity of households to store solid waste also has to be taken into consideration.
In informal settlements and other low income communities, houses do not have the
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8. Solid waste collection and transport
capacity (due to limited space) to store waste for more than one day. The same problem
is faced in city centres where commercial and service provision establishments not
only have insufficient storage space but also produce a considerable amount of waste.
In all such cases daily waste collection is preferable.
8.1.4
Collection times
To significantly reduce costs and optimize the use of collection vehicle fleets, if possible,
collection should always be done in two shifts.
To obtain maximum performance the ideal usage of the collection fleet would be:
Collection days
First shift
Second shift
Monday, Wednesday and Friday
¼ of the routes
¼ of the routes
Tuesday, Thursday and Saturday
¼ of the routes
¼ of the routes
If for example, 24 collection routes are established, with a collection frequency of
three times a week, the number of collection vehicles required would be 24÷4= 6 (with
an additional reserve representing at least 10% of the operational fleet, in this example
one extra vehicle).
It is recommended that the day is divided into two 12 hours periods with one eight
hour working shift in each period. The first shift for example, could begin at 07.00 hrs
and the second at 19.00 hrs, so that there would be an interval for maintenance and
repair services between the two shifts.
In many Latin American and Caribbean cities the ideal of two waste collection shifts
per day is not possible due to the type of urbanization that exists in some
neighbourhoods where, for example, access streets are precarious and street lighting
is scarce, which can make a nocturnal collection shift impossible. The issue of urban
violence should also be considered here.
In streets and public areas where sweeping services are not frequent the cleanliness
of the collection operation is very important, that is, it is necessary to collect the
refuse put out for collection without leaving any refuse scattered in the street.
Whenever possible, sweeping should be done after a collection to remove any refuse
that may have been left scattered in the area.
93
In central and commercial zones collection should take place at night when the circulation
of people and vehicles has diminished. In tourist cities collections should avoid the
hours of peak tourist activity in relevant locations.
The determination of collection times should also take into account the parking of
private vehicles in streets.
In purely residential neighbourhoods it is preferable that collection takes place during
the day but avoiding the times when there is more traffic on the principal roads.
During night time collections all necessary measures should be taken to reduce
noise. The collection team should be instructed not to raise their voices. The team
leader’s stop/start commands should be given through a switch at the back of the
truck connected to a light in the drivers cab. The truck’s engine should always be
well tuned and its silencer in good condition. In the case of a collection truck with
compaction facility the motor should not be revved up to accelerate the cycle of
compaction but should at all times have its automatic acceleration device functioning.
In the future more modern and silent vehicles may be needed, electric ones perhaps,
to respond to an ever more demanding general public, particularly in large urban
centres.
8.1.5
Restructuring domestic collection routes
Some of the factors that indicate a need for the restructuring of collection routes are:
increases or decreases in the population, changes in the characteristics of
neighbourhoods and an irregular collection service. Several elements should be taken
into account, such as:
Collection teams
In Latin American and Caribbean cities teams have from two to five members per
truck. Municipal teams tend to have more members than those of private companies
that provide collection services, reflecting the tendency for higher productivity with
private labour.
A team is the group of workers assigned to a collection vehicle to
perform solid waste collection activities.
Equilibrium between routes
The tasks assigned to each collection team have to represent the same amount of
work, so that the physical effort required of the different teams is equivalent.
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8. Solid waste collection and transport
In zones with high concentrations of waste collectors carry a lot of weight but
walk relatively short distances, whereas in zones with low concentrations of waste
they carry less weight but walk further. In both cases, the amount of calories
consumed can be approximately the same. The physical notion involved is that of
“work”:
work = force x distance
The restructuring method described here is one of the more simple ones and consists
of the division of the area to be restructured into “sub-areas” with a similar demographic
density and waste concentration (measured in kg/m). Each of these sub-areas can
then represent the same amount of work and working time. It should also be taken
into account that different workers have different physical constitutions and teams
should be balanced in this respect.
Collection route starting points
Routes should be laid out in such a way that teams begin at the point farthest from the
destination of the waste so that as they work they are diminishing the remaining distance
to be covered. The location of the fleet garage is another factor to be heeded in
planning.
Verification of the amount of domestic waste generated
It is important to verify the amount of solid waste that is generated in households,
public establishments and commercial premises, as this data is essential for an effective
restructuring of regular waste collection routes.
Although it is possible to calculate the per capita domestic waste generation rate through
the simplified method explained in chapter 5, ideally a more precise technical evaluation
of this parameter should be made, given the great variations between the different
zones of a city. Such variations could distort the dimensions of collection routes which
would then require considerable adjustment during the implementation phase of a
new collection program.
Data collection must include statistical data from high, medium and low income
neighbourhoods. Using data projection based on the latest available census, daily per
capita waste generation can be calculated.
As has already been mentioned, a certain technical rigour should be applied to the
determination of this rate as it can vary between 0.35kg and 1.00kg per person per day
in different areas of the city, depending on the socioeconomic stratum of the
inhabitants. In most small and medium-sized Latin American and Caribbean cities the
average per capita generation is between 0.50 and 0.80 kg/inhab/day (see chapter 5,
table 6 – Frequently used categories for determining per capita solid waste generation).
95
Where for example the daily per capita solid waste generation is 0.70kg and the
population is 200,000, the weight of waste generated daily for collection will be:
200,000 inhabitants x 0.70kg/inhab/day = 140,000kg/day
This data is essential for calculating the required number of vehicles in the domestic
waste collection fleet.
The calculation of per capita waste generation can be done at the same time as studies
to determine solid waste characteristics.
In practice, the restructuring of collection routes can be more complex and involve
other variables that the planner has to take into account.
When the restructuring plans are ready the new routes can be used for two weeks,
after which problematic details can be adjusted.
Lack of a weighbridge to weigh waste
If there is no weighbridge to weigh truck loads of solid waste at its destination, an
alternative should be sought such as gaining access to the weighbridge of a company
or public body.
Should this prove impossible, a simplified approximate method, called cubing, can be
used to restructure collection routes on the basis of the volume of collected waste.
To calculate the amount of waste by cubing a standard receptacle of known capacity,
for example 100 litres, is used, and is repeatedly filled and emptied until all collected
waste has passed through it.
The number of times that the receptacle is emptied into the collection truck is counted
to determine how many times it is filled during a collection from one street block.
This method consists of:
!
doing the cubing per block on the days of the week with more waste production, in
general Mondays and Tuesdays;
!
writing down on a map the number of receptacles per street block; see example in
figure 20;
!
progressively adding up the number of receptacles per street block, following the
itinerary of the route, until the truck is full, repeating this process for each trip in
each shift. In this way the total number of receptacles per trip and the number of
trips per shift, per vehicle can be determined;
!
on pronounced slopes collections should be made beginning at the top and working
downwards to save the energy of the team and the fuel of the truck;
!
test the new routes in practice, recording times, so that necessary adjustments can
be made.
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8. Solid waste collection and transport
Figure 20 - Example
A street block is each one of the sides of a block in the city.
Collection route layouts
Collection routes should be laid out in such a way that unproductive stretches are
minimized, that is those along which there is no waste to collect.
Routes should be designed through successive experimentation with a view to finding
the optimum one that at the same time responds to conditions such as the direction
of one-way streets, the avoidance of left turns in two-way streets and duplicated or
unproductive stretches. Collection route layouts tend to be arrived at through the
“heuristic” method, taking into account the direction of traffic, pronounced slopes
and ease of access and manoeuvre for the vehicles.
See figure 21 for an example of a rational collection route (heuristic method)
Figure 21 - Heuristic method collection route layout
97
Collection route restructuring method
This method consists of:
!
dividing the city in sub-areas;
!
surveying and systematizing the characteristics of each route;
!
analyzing the collected data;
!
restructuring routes based on:
!
the elimination (or minimization) of overtime;
!
the new weight of waste for collection per shift;
!
the concentration of waste in each area.
A city where the collection routes need to be restructured has to be divided into subareas of similar demographic density, for example, sub-areas I, II and III. Let us suppose
that in sub-area II there are currently eight collection routes, covered in two shifts
three times a week by two compaction vehicles. The data for the current program can
be seen in table 13.
Sub-area II
I – Commercial sub-area
Sub-area I
II – Predominantly residential sub-area
III – Hills sub-area
Sub-area III
Figure 22
Table 13
Current routes – Mondays and Tuesdays
Routes
Length of
route
m (1)
Weight
of waste
Kg (2)
Average
time of
work
hrs* (3)
Workers per
team
(4)
Kg/hr
(2)/(3)
Kg/m**
(2)/(1)
01
14,250
16,400
8.20
4
2,000
1.15
4,100
02
13,180
14,200
7.72
4
1,839
1.08
3,550
03
14,600
17,300
8.75
4
1,977
1.18
4,325
04
16,410
19,500
8.99
4
2,169
1.19
4,875
05
15,120
18,100
9.78
4
1,851
1.20
4,525
06
18,040
17,400
8.65
4
2,012
0.96
4,350
07
13,870
15,600
9.36
4
1,667
1.12
3,900
Kg/Worker
(2)/(4)
08
15,660
18,300
10.01
4
1,828
1.17
4,575
Averages
15,141
17,100
8.93
4
1,915
1.13
4,275
Totals
-
153,900
-
-
-
-
* hours calculated in decimals
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Rates
-
** kg/m = waste concentration
8. Solid waste collection and transport
With a normal work shift of 8 hours, it can be seen that the time used to complete the
routes is too much and therefore requires overtime (based on the supposition that
the collection is done regularly).
If the objective is to finish the collection in eight hours and thus avoid overtime, the
weight to be collected per working shift can be calculated assuming no change in the
productivity of collectors.
W = kg/h x Ts
Where Ts is the duration of the work shift (8hours in this case). Therefore:
W01 = 2,000 x 8 = 16,000kg
W05 = 1,851 x 8 = 14,808kg
W02 = 1,839 x 8 = 14,712kg
W06 = 2,012 x 8 = 16,096kg
W03 = 1,977 x 8 = 15,816kg
W07 = 1,667 x 8 = 13,336kg
W04 = 2,169 x 8 = 17,352kg
W08 = 1,828 x 8 = 14,624kg
Total weight 112,744kg
Average weight 15,343kg
As the weight that can be collected in an eight hour work shift is 15,343kg, uncollected
waste would amount to:
153,900kg – 112,744kg = 31,156kg
As the average collection weight for new routes would be approximately 15,343kg/
route, it will be necessary to initiate:
31,156kg ÷ 15,343kg = 2.03 new routes
That is, in practice two routes more, one on Mondays, Wednesdays and Fridays and the
other on Tuesdays, Thursdays and Saturdays.
As in future the area will be covered by 10 routes, the average weight per route will be:
153,900kg ÷ 10 routes = 15,390kg/future route
Future routes should be marked on the map taking into account the concentration of
waste in each area (expressed in kg/m).
To achieve this, the length of each route is multiplied by the waste concentration until
obtaining an approximate weight of 15,390kg/route, applying the formula:
LxC=W
Where:
L = length of route (m)
C = waste concentration (kg/m)
W = average weight of future routes (kg)
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In the example, the average weight of the future routes will be approximately 15,390kg.
The number of vehicles will be: number of routes ÷ 4 = 2.5
So, three vehicles can be used during the first shift and two during the second. The
type and capacity of the vehicles depend on the number of journeys that are necessary
to the final disposal site. For example, if on Mondays and Tuesdays two journeys are
necessary, the average load per journey would be 15,390kg ÷ 2 = 7,695kg.
When it is raining the weight of waste increases by 20%. Fluctuations in the number of
tourists also have to be taken into account as they cause increases or decreases in
waste production.
8.1.6
Collection vehicles
There are two types of specialized vehicle in general use for domestic waste collection
and transport:
!
compactors – rear loader or side loader;
!
without compaction – with the box closed by sliding doors.
Particularly in smaller cities with limited budgetary resources conventional open dump
trucks are frequently used as well as other equipment described later.
A good domestic waste collection vehicle should have the following characteristics:
!
that it does not spill waste or leachate on the street;
!
a compaction rate of at least 3:1, that is 3m³ are reduced by compaction to 1m³;
!
a waist high loading height of no more than 1.20m from the floor;
!
the possibility of emptying at least two receptacles at the same time;
!
rear loading (preferably);
!
adequate space for transporting the team;
!
fast unloading of waste at its destination;
!
a loading compartment capacity of at least 1.5m³;
!
good manoeuvrability and potency for steep inclines;
!
lifting devices to empty different types of containers;
!
even load distribution on the truck’s chassis;
!
adequate carrying capacity to minimize the number of journeys to the waste
destination while at the same time being appropriate for the characteristics of the
operational area.
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8. Solid waste collection and transport
Figure 23 - Containers being emptied into a compaction truck
Solid waste collection operations involve dangers for the collection personnel. Every
time the vehicle stops the team is exposed to the risk of injury through other vehicles
colliding with the rear of the collection truck.
The risk of being run over is high and efficient preventative measures must always
be taken.
In compactor vehicles it is essential to always take precautions with the compaction
mechanism. In addition adequate space should always be available on the truck for the
collection team.
Therefore, the most recommendable technical solution is to use compactor collection
vehicles wherever possible. However, due to the characteristics of a particular urban
area, sometimes this is not an option for operational or economic reasons.
In such cases the most cost efficient type of vehicle and equipment should be selected.
The vehicle that is chosen should be the one with more of the above listed
characteristics while taking into account the particular conditions of the service
provision area (the condition of the streets, topography, manoeuvring conditions, etc.).
Some vehicles and equipment in general use for domestic waste collection are described
below.
101
Closed box collection trucks
A solid waste collection vehicle without compaction, appropriate for working in small
communities with a low demographic density. It can also be used in areas with
pronounced inclines. The box volume can vary from 4 to 12m³ corresponding to a
truck total gross weight (TGW) of from 7 to 12 tons.
Total gross weight (TGW) = chassis weight + box weight + load weight.
Unloading is by hydraulic box tipping. This truck represents a low cost option in terms
of both purchase and maintenance but has quite a low productivity. It requires great
physical effort from the collection team who have to lift the waste up to the edge of
the box, which is more than two metres high, much higher than the compactor collector
loading compartment height of approximately one metre.
Figure 24 - Closed box truck
Compactor collection trucks
Solid waste compactor collection trucks, which are usually rear loaders but can be side
loaders, are made of steel and have a capacity of 6, 10, 12, 15 or 19m³ corresponding
to a truck TGWs of 9, 12, 14, 16 and 23 tons respectively. They may have hydraulic
devices for the automatic and independent unloading of standardized containers.
This type of vehicle is used for domestic, public and commercial waste collection,
especially in zones where there are high concentrations of solid waste from large
generators or a high demographic density. Its use can be limited by unfavourable road
conditions such as irregular layouts, unpaved and potholed surfaces, or roads unsuitable
for heavy vehicles.
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8. Solid waste collection and transport
Figure 25 - Side loader compactor collection truck – 6m³
Figure 26 - Rear loader compactor collection truck – 10 to 15m³
Figure 27 - Rear loader compactor collection truck – 19m³
Dumpster carrier trucks for 5m³ stationary containers
Domestic waste collection systems that employ 5m³ stationary containers replaced by
dumpster carrier trucks with multifunctional crane are appropriate for zones with low
quality houses or difficult access. Containers are located at strategic points close to
103
the communities they serve but with easy access for the dumpster carrier trucks that
replace loaded containers with empty ones.
There are two types of dumpster carrier truck with differing operational capacity:
!
single - that transport only one 5m³ stationary container at a time;
!
double - that can transport two 5m³ stationary containers at the same time.
Stationary compactor (compaction container) collection trucks
For the collection of large volumes of domestic waste special stationary metal containers
incorporating a compaction device can be used. These containers are called stationary
compactors, in general have capacity for 7 to 20m³ of loose waste and are transported
on special vehicles. The 7m³ capacity stationary compactors can be transported by
dumpster carrier trucks with multifunctional crane, while those with greater capacity
are transported by roll-on / roll-off trucks.
In big cities this system is slowly replacing the system of open stationary containers
transported by dumpster carrier trucks with multifunctional crane because, being more
hermetic and having a greater waste storage capacity, compaction containers offer
aesthetic, sanitary and economic advantages.
Figure 28 - Compactor container
Traditional dump truck type collection vehicles
These open box vehicles without a compaction device and not specifically designed
for domestic solid waste collection are frequently used in small communities with a
low demographic density and in areas of rough topography where it is difficult to
manoeuvre bigger compactor trucks. As with closed box collection trucks, unloading is
by tipping the box, the volume of which can vary from 4 to 12 m³ in trucks that
correspondingly vary from 7 to 12 tons TGW.
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8. Solid waste collection and transport
This type of vehicle is attractive for small municipalities due to its operational flexibility.
It can be used for various different activities, not only waste collection, and is therefore
appropriate for small cities where, due to the low level of waste production, a
specialized vehicle would be unused for significant periods of time. Another advantage
is its low purchase and maintenance costs.
The main disadvantage for domestic waste collection is that the box is open and it is
therefore difficult to keep the load inside it (particularly lighter waste) and avoid it
being scattered by the wind along the route. In order to minimize this problem, canvas
or plastic sheeting can be used but in practice the efficiency of this is questionable as
it significantly reduces the productivity of the collection team. Productivity is also
negatively affected by the loading height of the box and this too should be considered.
Special solid waste storage systems serviced by dump trucks equipped with a hydraulic
crane are now available on the market. Amongst them is the “Molok” system that can
be considered as an option in special situations, including in informal settlements, due
to its operational, aesthetic and sanitary advantages when compared with other more
conventional systems. However it is necessary to carry out a viability study before
implementing this system as it requires significant initial investment for purchasing the
containers, plastic bags, etc. Figure 29 shows this system in operation.
Figure 29 - Dump truck with crane moving a special “Molok” container
8.1.7
Tools and implements used by collectors
It is important that collection teams collect domestic waste without leaving any of
it scattered around. For this purpose medium-sized sweeper brooms and shovels
should be used.
105
A medium sized sweeper broom has a wooden base with 22 holes into which natural
fibres or recycled plastic bristles are fixed. These days the latter are increasingly
being used.
8.2 Public solid waste collection and transport
8.2.1 Concept
Public solid waste collection includes the collection and transport of waste gathered
as a result of routine and emergency street cleaning activities, such as sweeping,
weeding, pruning and special waste collection (for example waste and mud deposited
in the street by flooding).
The method, vehicles and equipment to be used in collection depend on the specific
nature of each individual cleaning operation, the type of waste generated and the
form of storage.
There are three basic categories that determine the collection method for public waste:
!
loose waste accumulated on the ground;
!
waste packed in plastic bags;
!
waste stored in wheelie bins or dumpsters.
Differences in specific weight and other physical characteristics of waste demand
different solutions for loading (manual or mechanical) and transport to a transfer station
or final disposal unit.
8.2.2 Collection of waste gathered by sweeping
Waste collected by street sweeping can be transported by the sweepers while
performing the service, for which purpose hand carts made of steel tubing with a
metal container (sweeper cart), wheelie bins or, on pronounced inclines, wheelbarrows
may be used.
Figure 30 - Sweeper cart, wheelbarrow and wheelie bin
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8. Solid waste collection and transport
In all cases it is recommendable that waste, which mostly comprises light material that
can be easily scattered by the wind, is stored in plastic bags for collection.
They can then be collected by compactor trucks (rear loaders or side loaders), which
are especially appropriate in large cities due to the high productivity of this type of
vehicle and the large volume of waste to be collected. The collection of this type of
waste at the same time as domestic solid waste represents an important device for
rationalizing collection and transport costs. Vehicles without compaction devices can
also be used: closed box trucks, traditional dump trucks or dumpster carrier trucks
that can handle stationary containers.
Because sweeping is undertaken in the more urbanized zones of the city it is important
to carefully plan the collection of this type of waste so that it remains on the street
for the minimum possible time, bearing in mind that a slower collection process could
adversely affect the municipal administration’s image of efficiency. As sweeping has
to be done in each zone as a programmed routine on pre-established days and at
specified times, it is completely feasible to integrate it with collection.
To determine the quantity of waste collected by street sweeping, it is necessary to do
a field survey in order to identify the average generation per sweeping route and, on
that basis, calculate the production of each sector. The generation of waste collected
by sweeping is influenced by various factors such as the predominant usage of the
street or public space, the level of environmental education of passers by, the type
and state of the surfacing on the street and pavement, as well as the characteristics of
any trees.
Depending on the type of trees, the generation of street waste can increase
considerably due to seasonal factors, that is, the falling of leaves and fruit onto
pavements and streets.
8.2.3
Collection of waste from weeding and vegetation cutting
Weeding and vegetation cutting activities generate vegetation waste that usually
accumulates in piles along the section of a street where the work has taken place.
From there it is carried by hand to the box of the collection truck (generally a
conventional dump truck).
An operational alternative that is sometimes adopted is to locate an open stationary
container near to the area where the work is taking place so that waste can be deposited
in it as the work advances. Such containers are subsequently removed by dumpster
carrier trucks with multifunctional crane.
When the dimensions of collection and transport services are being determined the
low specific weight of this type of waste should be taken into account as it results in
the load capacity of the collection truck being under used. The integration of this
waste’s collection with the collection of soil and sands that have accumulated on the
streets is an option for utilizing the truck’s full load capacity.
107
The identification of nearby locations appropriate for the disposal of this waste, eroded
areas for example, can also reduce the cost of transport, but appropriate sanitary and
environmental care should always be taken in disposing of it.
The necessary dimensions of the collection fleet are assessed by experienced operators
during a pre-operational visit to the site on which weeding and land clearing services
will be undertaken.
8.2.4
Tree pruning waste collection
Tree pruning is often linked with the municipal urban cleaning sector. Due to the nature
of this activity it usually requires the support of a truck to transport tools, implements
and labour. It is therefore often natural that the same truck is used to collect the
waste generated as work progresses.
This type of waste includes loose leaves, small branches and thick trunks, and its
physical characteristics mean that when it is loaded into the box of the truck many
spaces are left unoccupied. Due to this low specific weight, the collection and transport
operation is relatively expensive and involves low productivity.
As with the disposal of weeding and land clearing waste, disposal sites that are near to
the generation site can be sought for pruning waste. The load can be prepared for
collection at the generation site using standard pruning tools (machetes, saws and
chain saws) to make the material more homogeneous and to prepare part of the waste
for reuse (the thicker trunks, for example).
Recently new technological alternatives have been incorporated in pruning
operations to address the low productivity and high cost of collection and transport
in cities that produce large amounts of such waste. A branch grinder can be an
important component of an economical and environmentally sound operational
solution to this problem. This is a robust and compact machine, available in towable
models, that can reduce by up to ten times the volume of a pruning waste load.
Another advantage of this system is that the ground waste is easy to dispose of in
appropriate nearby locations as the final product has a low granulometry and can
be used as coverage for natural soil, minimizing erosion risks and incorporating
organic matter.
Pruning operations tend to use a fixed box truck with a special elevation platform to
raise the worker for the cutting of higher tree branches.
108
8. Solid waste collection and transport
8.2.5
Collection of rubble and other construction waste
This type of service can be provided directly by the public administration or by
authorized private companies. In the latter case previous authorization is needed so
that the identity of service providers is known and their activities can be overseen on
an ongoing basis in order to prevent the clandestine disposal of waste in inappropriate
places.
Basically there are two types of situation that require rubble collection services:
!
where rubble has been clandestinely disposed of in the street, on wastelands or on
the banks of bodies of water;
!
where generators of this type of waste request or contract services.
In the first case it is clearly the responsibility of the public administration to collect
construction rubble that has been indiscriminately disposed of in the city, a responsibility
that requires the urban cleaning body to maintain the necessary infrastructure for this
purpose. Where requests for collection are made by generators it is recommended
that this service is provided by the municipal urban cleaning system only to small volume
generators (there should be a specific municipal regulation on this subject). Where
construction works produce larger amounts of rubble the “polluter pays” principle
should be applied.
Whoever provides the service it should be scheduled, with the cooperation of the
generator, for the day and time most appropriate for waste collection taking into account factors such as the traffic flow and parking conditions in the street closest to
the place of generation. Service provision should be organized not only to coordinate
requests that have been granted and to incorporate field survey data, but also to
ensure a rational route that minimizes unproductive journeys and maximizes operational productivity.
Construction rubble collection is in general undertaken by conventional dump trucks
or 5m³ stationary containers transported by dumpster carrier trucks with multifunctional crane.
8.2.6
Special collections
This type of service is necessary in certain situations, which regrettably are common in
Latin American and Caribbean cities, where inappropriate waste accumulation sites or
clandestine rubbish dumps arise, generally located on wasteland or unoccupied plots.
The expression “rubbish attracts more rubbish” summarizes the underlying causes of
this type of accumulation: small volumes of pruning waste for example are left in a
particular place, this may then be added to by other people disposing of construction
rubble there. Subsequently local residents add plastic bags of residential waste and in
a short time there is a large accumulation of waste that causes serious sanitary and
environmental impacts.
109
In general the existence of waste accumulation sites and clandestine refuse dumps
results from operational defects in the regular domestic waste collection and street
cleaning system together with deficiencies in the supervision of municipal activities.
The lack of attention to these issues by those responsible for urban cleaning means
that the causes of this serious problem are not addressed but only its consequences,
and thus new cases repeatedly arise necessitating more and more special collection
services.
Due to the large amount of waste that accumulates on such sites, collection
operations may require mechanical loading equipment (mechanical loader), rather
than a manual operation, and large vehicles for collection and transport to the final
disposal site.
8.2.7
Vehicles and equipment used for collection
Dumpster carrier trucks with multifunctional crane for handling 7 ton containers
A truck (minimum total gross weight 13.5 tons) with a mounted minimum 7 ton capacity
hydraulic crane for lifting and transporting open metal containers loaded with solid
waste. These trucks can be single carriers to transport one container at a time or
double carriers to transport two containers at a time.
To be productive they have to operate over short distances between container
locations and the unloading site.
Figure 31 - Dumpster carrier truck with multifunctional crane
110
8. Solid waste collection and transport
Short dump truck
A two axle vehicle for the collection of public waste, construction rubble and earth
with a box of 5 to 8m³ capacity with a respective truck TGW of from 12 to 16 tons.
Figure 32 - Short dump truck
Long dump truck
A three axle vehicle for the collection of public waste, construction rubble and earth.
The box generally has a 12m³ capacity and the truck a TGW of 23 tons.
This truck is usually loaded by a mechanical loader to reduce human effort and increase
productivity.
Figure 33 - Long dump truck
Roll-on / roll-off container carrier truck
A collection truck with devices for lifting 10 to 30m³ stationary containers without a
compaction device (figure 16). Each vehicle should handle six containers for its
productivity to justify its use.
These three axle trucks should have a TGW of 23 tons.
111
Semi-trailer
A semi-trailer dumper with capacity of 25m³ pulled by a 4x2 truck with a 45 ton pulling
capacity. It can be used to transport rubble or in support of large earth or mud collection
operations. It is loaded by mechanical loader and is unloaded at the final destination by
box tipping.
A semi-trailer is a trailer the front part of which has to be supported on a towing
vehicle called a semi-trailer truck.
A canvas or plastic sheet should cover the top of the box to avoid waste being scattered
in the road by the wind while the vehicle is moving.
Figure 34 - Semi-trailer
Mechanical loader
A wheeled tractor loader used to pile up earth, rubble, mud and waste, and to load
dump trucks, dumper boxes and semi-trailers in street cleaning operations and at waste
accumulation sites.
For street operations machines with a scoop capacity of 1,5m³ are normally used,
while for loading semi-trailers it is advisable to use machines with a 3m³ scoop to
increase productivity and because of the higher loading level.
Figure 35 - Mechanical loader
112
8. Solid waste collection and transport
8.3
Waste collection in tourist cities
The amount of waste to be collected varies according to tourist season related
population fluctuations as well as the usual all year round fluctuations.
As the usual fluctuations (weekly and monthly) have little effect on the size of the
fleet that is needed, this section will deal with the necessary procedures for maintaining
the quality of domestic waste collection in tourist cities during the season of population
influx.
The basic measures to take are:
!
the introduction of overtime for collection workers, within the limits imposed by
employment legislation;
!
an increase in the number of collection shifts;
!
the utilization of the reserve fleet in operations;
!
the contracting of extra vehicles from private companies or individuals.
Whenever possible the contracting of extra vehicles should be planned in advance to
avoid overpricing.
It is important to note that these measures should be taken in sequence in order to
limit the increase in collection costs to a minimum.
Other important factors to take into account are:
Traffic
In tourist cities the traffic is usually congested during holiday periods, which impedes
the movement of collection vehicles and increases the time taken to cover collection
routes. Waste collection schedules should therefore be set for times when traffic is
less heavy.
Beaches
In coastal cities where tourists tend to concentrate around the beaches, collection
routes that cover streets bordering the sea should be revised and restructured in
order to adapt them to seasonal requirements, not only in regard to the increased
amount of waste but also the frequency and times of collection.
A reduction in the frequency of collections should never be considered, even though
it may be attractive for economic reasons, as the longer the interval between
collections the greater the danger of waste accumulation sites appearing in the streets,
which are detrimental to the city’s sanitary and environmental condition and discourage
tourists.
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8.4 Solid waste collection in informal settlements
There are informal settlements in many Latin American and Caribbean cities due to the
poor socioeconomic conditions experienced by a significant sector of the population
in the region.
A lack of basic urban infrastructure in these communities causes significant obstacles
for the provision of domestic waste collection services:
!
difficult access for conventional collection trucks;
!
inadequate or nonexistent preparation and pre-collection storage of waste;
!
the tendency of inhabitants to discard waste immediately after generation as there
is minimal space inside the houses.
These factors have to be taken into account in planning alternative waste collection
systems in these communities with a view to improving a situation that presents serious
risks to public health and the environment.
One solution to the problem of access through narrow internal streets, often with a
pronounced incline, is the use of special vehicles that are narrow, have good
manoeuvrability and the capacity to deal with steep slopes.
Mini-tractors or agricultural tractors with 4x2 or 4x4 drive towing 2,5m³ capacity trailers
with metal or wooden boxes are feasible alternatives.
(4x2) – two axle vehicle with rear wheel drive.
(4x4) – two axle vehicle with four wheel drive.
Figure 36 - Micro tractor
Figure 37 - Micro tractor and dump trailer
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8. Solid waste collection and transport
As these vehicles are not appropriate for long journeys, the collected waste is
transported to a temporary storage place where it is kept for subsequent transport
to a final disposal site. It is normally recommended that stationary containers are
used for this temporary storage and they are then either transported by special
collection vehicles (dumpster carrier trucks) or emptied into large compactor trucks.
When installing open containers in informal settlements it is necessary to take the
precautions already mentioned in chapter 7 in order to avoid a prejudicial proliferation
of insects and animals. If appropriately clean conditions and supervision are not
maintained there is a risk of people setting fire to the waste.
The problem of pre-collection waste storage in these areas can be dealt with by siting
containers along the micro tractor collection route, preferably plastic containers with
lid and wheels.
The frequency of collections should be carefully considered and ideally there should
be only short intervals between them, daily collection being the best option.
It has to be pointed out that in many of these communities it is not even possible to
use the mini-tractors for collection due to a lack of passable access. In such cases
collection should be manual, with the waste being carried to some point that is accessible
for some type of vehicle.
In several cities the contracting of community collectors has produced good results. In
these cases, the municipality contracts the community centre, for example, which then
selects the people who will work in the collection team (as well as carrying out weeding
and channel cleaning tasks, etc.).
It is worth noting that contracting community collectors involves the principle of
community participation as it encourages other residents to participate in the
maintenance of the place where they are living as they may feel an obligation to keep
public areas clean when it is one of their neighbours who is doing this work.
8.5 Collection of medical waste
8.5.1 Acknowledgement of the problem
Hygienic conditions in health service establishments (hospitals, clinics, medical centres,
veterinary clinics, etc.) are fundamental for the prevention of infections. Regular cleaning
with germicide solutions keeps floors, walls, roofs and furniture free of dust, body
fluids and any waste from medical activities. Appropriate internal transport and storage
together with subsequent collection and external transport of waste complete the
measures aimed at reducing infections.
115
In hospitals medical waste generation rates are related to the number of beds. Table
14 shows waste generation per bed in some countries and in Rio de Janeiro city.
Table 14
Medical solid waste generation rates
Place
Average generation kg/bed/day
Chile
0.97 – 1.21
Venezuela
3.10
Argentina
1.85 – 3.65
Peru
2.93
Paraguay
3.80
Brazil
2.63
Rio de Janeiro
3.98
Medical waste is classified as common, infectious or special (see table 4).
Hospital areas are classified in three categories:
!
critical areas: where there is a greater risk of infection such as operating theatres,
delivery rooms, infectious disease isolation rooms, laboratories, etc.
!
semi-critical areas: where the risk of contamination is less, such as the rooms occupied
by patients with non-infectious diseases, nurses’ rooms, laundries, refectories and
kitchen areas etc.
!
non-critical areas: where in theory there is no risk of infection, such as administration
rooms, storerooms, etc.
8.5.2
Segregation
There are regulations that must be followed for the segregation of infectious and
common waste in health service establishments:
!
at the time of its generation all infectious waste should be put in a receptacle close
to the place where it is produced;
!
infectious waste must be stored in accordance with stipulated technical standards,
in well closed plastic bags (generally coloured cream);
!
puncturing and sharp waste (needles, glass, etc.) should be stored in special
receptacles specifically for this purpose;
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8. Solid waste collection and transport
!
waste from clinical analysis, blood transfusion therapy and microbiological research
should be sterilized in the place of generation;
!
infectious waste consisting of human body parts, organs and tissues should be
separately put in cream plastic bags that are then appropriately closed.
8.5.3
Separate collection of common,
infectious and special waste
Infectious and special waste should be separated from common waste before collection.
Radioactive waste should be dealt with in accordance with each country’s specific
regulations issued by the respective governing body.
Infectious waste and the rest of the special waste should be stored in cream plastic
bags which are put into standardized containers that are mechanically emptied into
special vehicles for medical waste collection. This waste represents at the most 30%
of the total medical waste generated.
If there is no separation of infectious and special waste all of the waste should be
packaged, stored, collected and disposed of as though it is infectious or special waste.
Current norms recommend that in most cases medical waste is collected daily, even on
Sundays.
8.5.4
Vehicles for collection and transport
As plastic bags with infectious or non-separated waste can break and release
contaminated liquids or air, collection vehicles should not have compaction systems
and, as an additional precautionary measure, must be hermetic and have liquid capturing
devices. Depending on their size they should have mechanical devices for both empting
the containers and unloading the vehicle.
Common waste generated in these establishments should be collected by the normal
collection service.
The types of vehicle usually recommended for medical waste collection are presented
below.
Van
A light van with the driver and passenger cab independent from the load compartment
and a load capacity of 500 kilos. The load compartment should be lined with fibre glass
in order to avoid the accumulation of infectious waste at the edges and in cracks and
to facilitate washing and cleaning.
Light vans with hermetic load compartments and a capacity for approximately 2m³ of
waste, are suitable for the collection of puncturing and sharp objects from chemists,
analysis laboratories, dental clinics and other similar establishments. In some cases it
117
may be economical for these vans to unload waste that they have collected in the
loading areas of bigger medical waste collection vehicles, which will then transport it
to the final disposal site.
Figure 38 - Van for medical waste collection
Truck for infectious waste collection
A two axle collection truck with a capacity of 6 to 8m³, without a compaction device.
A tipping system may be incorporated for the emptying of plastic or metal containers
with a capacity of up to 700 litres. The box is made of steel with continuous welded
seams to avoid liquid leakage and has a compartment for capturing liquid originating
from the load with a device for unloading it in an appropriate place. The rear door of
the load box must close with an efficient seal. The unloading of waste is done
through the tipping of the load box after the rear door has been fully opened. The
hydraulic powered system is coupled with the gearbox and is pneumatically operated
from inside the cab. Amongst the chassis recommended are: VW 8150, MB 914 and
Ford Cargo 81.
Figure 39 - Truck for infectious waste collection
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8. Solid waste collection and transport
8.5.5
Aspects of collection planning
When planning the collection of this type of waste a determination should be made,
together with the generators and the responsible health authority, of the amount of
waste generated in each establishment and the possibilities for treating it at source,
while at the same time establishing appropriate methods for its pre-collection
preparation and internal storage.
The steps to follow include:
!
locate on a map all health establishments: hospitals, out-patient departments,
chemists, medical centres, emergency services and clinics;
!
based on collected data, determine the necessary type, size and number of collection
vehicles, the frequency of collections and collection routes;
!
select van type collection vehicles with leak-proof load compartments and liquid
retention trays;
!
train the service operation teams, including in measures for their own protection
and work safety practices.
The basic guidelines for rationalizing costs and establishing an appropriate service
management policy are the following:
!
facilitate treatment;
!
prevent contamination;
!
intensify safety measures;
!
avoid work accidents;
!
maintain an organized and pleasant work environment;
!
acknowledge employees’ work;
!
reduce absenteeism.
To achieve good quality medical waste management it is important to
instigate educational processes that prepare people for change.
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9
120
Solid waste transfer
9. Solid waste transfer
9.1 Concept
At the same time as large and medium-sized cities have experienced intense urban
expansion there has been an increase in both environmental pressures and the
resistance of residents to accepting the installation close to their homes of facilities
related with solid waste final disposal. In addition urban land is too expensive to be
used for sanitary landfills, for which large areas are required. Consequently final disposal
sites are being established further and further away from centres of large-scale waste
generation. This increased distance between collection areas and sanitary landfills
creates the following problems:
!
delays in completing collection routes thus prolonging the time that waste is exposed
on the street;
!
increased unproductive time that collection teams spend waiting for the return of
the truck from unloading at the landfill;
!
increased transport costs;
!
reduced productivity of collection trucks, which are specialized and therefore
expensive vehicles.
To solve these problems some municipalities are establishing transfer stations.
Waste unloaded in transfer stations is transported to the sanitary landfill by a larger
vehicle that involves lower transport cost per unit.
Vehicles used for transporting waste from transfer stations to final disposal sites
usually have three times more load capacity than collection trucks.
In general transfer stations begin to be considered when the distance between
the location of large-scale collection activities and the sanitary landfill is greater
than 25km. In large cities where traffic conditions make travel very slow, transfer
stations are sometimes used even when the distance to the sanitary landfill is
shorter.
Transfer stations are units sited close to areas of large-scale waste
generation so that collection trucks can unload there and return
rapidly to continue their collection route.
The establishment of a transfer station should be preceded by a feasibility study that
evaluates the economic and operational advantages that it could provide to the collection
system.
121
Modes of transport from transfer stations can be:
Train – suitable for long distances or for cities where traffic on roads to the final
disposal site is too congested. This requires a complementary system of trucks to
transport waste from the unloading site to the sanitary landfill.
Boat – suitable for long distances and an excellent option in cities that have navigable
rivers or bays. Ideally waste should be transported in closed containers to avoid
scattering.
A complementary system of trucks is required to transport waste from the unloading
site to the sanitary landfill.
Truck – the most used system, recommended for transporting over medium distances
and in places where the traffic on roads to the final disposal site is not too congested.
9.2
Types of transfer station
9.2.1
Direct transfer station
This is a commonly used type of transfer station. It has a drop between the unloading
platform and the loading area, so that a collection truck on the higher level unloads
directly into the transfer truck below.
As there is no space for waste storage in these stations, a larger fleet of transfer
vehicles is required to avoid collection trucks having to wait too long to unload.
Figure 40 – Direct transfer station
9.2.2
Station with storage facilities
In most cities all collection trucks begin their routes at the same time and so it is
probable that the vehicles become full and arrive at the transfer station within the
same timeframe. The simultaneous arrival of vehicles makes it indispensable that the
station has an appropriate place for the storage of waste to deal with unloading “peaks”.
Waste storage also facilitates the operation of the system with fewer vehicles. Amongst
the more commonly used models for transfer stations with storage facilities are:
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9. Solid waste transfer
Station with silo storage and compaction
The main objective of these stations is to increase the specific mass of waste in order
to reduce transport costs. The traditional model has a storage silo and a drop between
loading and unloading platforms. A hydraulic system installed in the silo compacts waste
inside the transfer vehicles.
When this equipment is used weight specifications for the transfer trucks must be
observed so that loads do not surpass the legal limits.
Figure 41 - Transfer station with storage and compaction
Station with silo storage without compaction
Some units have storage silos to receive waste brought by collection trucks. Hydraulic
digger type machines load waste from the silos into transfer vehicles. This model is
more appropriate for stations that receive a maximum of 1,000 tons per day as in
larger units it would imply excessive construction costs.
Station with floor storage without compaction
Another model commonly used is that of floor storage stations. These stations have
covered paved floors with closed sides to avoid the exposure of waste to the elements
and improve the aesthetics of the establishment. The loading of transfer vehicles is
done by hydraulic diggers or mechanical loaders. This model facilitates the fast unloading
of collection trucks and loading of transfer vehicles, and can be used in small or large
stations.
Figure 42 – Station with storage without compaction
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9.2.3
Alternative transfer systems
The transfer station concept, although originally developed to respond to the needs
of large cities, can be incorporated on a smaller scale in special situations in small
communities where access is not possible for conventional collection vehicles. For
example, an alternative collection system using carts pulled by animals to cover
streets that are not accessible to collection trucks, may involve the unloading of
collected solid waste in a stationary container (or equivalent receptacle) at a site
where larger vehicles do have access and can collect the waste and transport it to
its final destination.
9.3
Vehicles and machines for transfer stations
To transport waste unloaded in transfer stations large interchangeable tipper containers
can be used, manoeuvred by vehicles equipped with cranes to lift them onto and off
platforms, or semi-trailers with or without compaction.
The models most used in transfer stations are: semi-trailer tippers and semi-trailers
with movable floor.
Semi-trailer tippers
A semi-trailer tipper towed by a 4x2 semi-trailer truck with a 45 ton pulling capacity. It is
loaded from a transfer ramp or by a mechanical loader or hydraulic digger, and unloaded
by tipping. The model most commonly used has a capacity of 45m³.
Figure 43 – A 45m³ semi-trailer tipper
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9. Solid waste transfer
Semi-trailer with movable floor
A semi-trailer with a capacity of 70m³, towed by a 4x2 semi-trailer truck with a 45 ton
pulling capacity. It is loaded from a transfer ramp or by a mechanical loader or hydraulic
digger, and unloaded by the alternating movement of the movable floor’s strips.
Figure 44 - A 70m³ semi-trailer with movable floor
In all open semi-trailers the load should be covered with plastic sheeting or a net to
avoid waste falling in the roads.
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10
126
Street cleaning
10. Street cleaning
10.1
The importance of street cleanliness
Up to the mid-19th century there was not only refuse in city streets but also the
remains of food and large amounts of animal and human excrement. The filthy conditions
in Europe during the Middle Ages are well documented, as are the plagues and epidemics
that they produced.
However, in several cities of the world for many centuries there have been laws and
municipal regulations prohibiting the discarding of waste and objects in the streets.
As a result of developments in medicine and sanitary engineering during the 19th century,
it was recognized for the first time that human waste not collected, treated and
appropriately disposed of is a significant source of disease and can provoke fast
spreading epidemics. The relationship between waste dumped in the street, the rats,
flies and cockroaches attracted by it and the transmission of diseases through those
vectors was also discovered. It was then that effective measures began to be taken
for the collection of domestic waste rather than allowing it to be thrown onto streets
or wasteland.
Flies and rats that proliferate in rubbish can transmit many diseases. They are called
disease “vectors”.
Most animal excrement (except for dog excrement) was eliminated from the streets
with the advent of motorized transport that replaced animal driven carts.
The surfacing of streets and the dissemination of hygiene and public health principles
in schools also contributed to the reduction of waste in the streets.
Keeping streets clean is important for the community and the collective interest must
be given priority over individual interests in order to respect the wishes of most citizens.
The principal motives for keeping streets clean are:
Sanitary
!
to prevent diseases caused by vector proliferation in waste accumulations on the
street or on wasteland;
!
to avoid damage to health caused by dust coming into contact with eyes, ears, nose
and throat.
Safety
!
to avoid damage to vehicles from branches and sharp objects;
!
to promote road safety by eliminating dust and earth that can cause skidding and
dry leaves and grass that can cause fires;
!
to avoid rain water drainage systems becoming clogged up.
127
Aesthetic
!
a clean city inspires pride in its inhabitants, improves the appearance of a place,
helps to attract new residents and tourists, increases the value of property and
stimulates business.
The aesthetic aspect of street cleanliness forms a significant part of arguments for
the implementation of policies and measures to improve the image of cities, particularly
so in tourist cities. Whatever the historical significance, landscape beauty or cultural
richness of a city, in the context of tourism it is hard for a visitor to leave with a
positive impression when a place is aesthetically ugly due to a lack of cleanliness.
While it is true that a tourist demands cleanliness of a city, it should also be noted that
he himself is in many cases contributing to its dirtiness.
In general the tourist does not establish an attachment with the place he is visiting, he
is a mere visitor, a consumer of space. Consequently his consideration for the place is
less intense than that of residents. In general people take more care of their own
houses than of spaces that do not belong to them.
In view of these attitudes, it is important that tourist city municipalities implement urban
cleaning education campaigns specifically addressed to visitors, with a view to maintaining
urban aesthetics and therefore contributing to an improvement in the city’s sanitary
conditions.
10.2
Waste found in the street
Waste commonly found in the streets:
!
material from road surface break-up;
!
rubber from tyres and residues from brake pads and linings;
!
sand and earth carried by vehicles or coming from wasteland and slopes;
!
tree branches and leaves, weeds and other vegetation;
!
paper, plastic, newspapers, packaging;
!
domestic waste (in general in small amounts, principally on wasteland and areas
close to informal settlements);
128
!
dog and other animal excrement (also in small amounts);
!
particles from atmospheric contamination.
10. Street cleaning
Figure 45 - A street considered as
“dirty”, with pieces of paper and plastic
in the gutters
Figure 46 - A street considered as “clean”, with no
visible refuse
The types of refuse that most offend citizens’ sense of hygiene and cleanliness are
papers, bits of plastic, packaging and the remains of food discarded in the street. A
gutter with some earth and material from road surface break-up is not perceived as
“dirty” by the general public while paper and plastic items are associated with “rubbish”
(i.e. types of waste that produce bad odours, have an ugly appearance and attract
undesirable animals).
More developed cities are giving increasing importance to a combination of cleaning
services and street conservation measures (maintaining street surfaces and pavements
in good condition, etc.) when defining quality standards for urban cleaning services
that are compatible with client-citizens’ ever more demanding criteria.
10.3
Street cleaning services
Street cleaning services in general include activities such as sweeping, weeding and
scraping; grass and vegetation cutting; drain cleaning; street market cleaning and waste
removal.
They can also cover other activities such as beach cleaning, the unblocking of drains,
pest control, disinfection, tree pruning, kerb painting and street washing.
129
10.3.1 Sweeping services
Characteristics of city streets
In surfaced streets most debris is found in the gutters (at the most 60 cm from the
kerb) due to the air displacement produced by passing vehicles that “pushes” dirt
towards the kerb.
In the streets themselves there is practically no dirt unless there is almost no traffic.
Rainwater also carries debris towards the kerb, in the direction of the drains, due to
the transverse curvature of the street. The gutters are in reality “channels” designed to
conduct rainwater.
Figure 47 - Cross section of a street
In non-surfaced streets dirt and litter behave in a different way and it is necessary to
clean the entire width of the street.
It is essential to take these characteristics into account when determining street cleaning
methodology.
Restructuring manual sweeping routes
Review of the existing sweeping plan
The organization of existing sweeping routes should be examined. The review of the
plan should register the street sections that are swept on each route, the length of
each one (expressed in metres of pavement and gutter) and the teams assigned to it
(sweepers).
Service quality
As there is no process for determining precisely the degree, quality and standard of
cleanliness that each street requires, those responsible for urban cleaning have to use
their own criteria. They will determine the methodology and frequency of cleaning and
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10. Street cleaning
will evaluate the approval or disapproval of the public according to the number and
content of complaints and suggestions received.
It is possible to gauge public opinion about cleaning services by carrying out opinion
surveys, investigating previous complaints and consulting press files.
Productivity tests
As each city has its own characteristics, habits and culture, it is advisable to evaluate
workers’ productivity in the field, that is, how many metres of gutter and pavement
can be swept per worker per shift.
This index is of fundamental importance for the restructuring of sweeping routes and
is usually measured in samples of typical residential, commercial and tourist streets,
and principal thoroughfares.
To carry out the tests, workers of medium performance are chosen and for a period
of approximately fifteen days the distance that each one sweeps in each type of
street is measured thus determining the average distance covered per shift.
Identification of sites that influence public opinion
Citizen participation is indispensable for public cleaning services to maintain an
appropriate level of cleanliness. Reference sites should therefore be established where
comparative studies can be made of resource mobilization and the quality of services
provide by the responsible body.
One of the first measures to take in order to improve services is the identification of
sites that influence public opinion, that is, certain streets that, if they are kept clean,
form and consolidate a favourable public opinion on the part of both residents and
tourists in regard to the cleanliness of the city, which then encourages the public to
cooperate in maintaining clean and hygienic conditions in the streets. These sites should
be photographed periodically to facilitate a comparative checking.
Tourist areas, principal streets and avenues, commercial centres and access roads to
the city are sites that influence public opinion.
Determination of sweeping frequency
The minimum sweeping frequency necessary to maintain the required level of cleanliness
in streets has to be determined.
This information is significant as, for example, if a street needs to be swept every day
double the number of workers will be needed than if it is swept every other day.
New sweeping plan layout
Once the existing plan has been examined and productivity indexes (metres of gutters
and pavements swept per worker per shift in each type of street), sites that influence
public opinion and minimum sweeping frequency for the different areas have been
determined, the new plan can be laid out on a map to a scale appropriate for the
relevant area.
131
Once the new plan is operational, the level of cleanliness achieved should be checked
through photos, and the reaction of the public should be evaluated through opinion
surveys and the registration of complaints, on the basis of which necessary adjustments
can be made.
Up to three workers can be assigned to each route but it is recommended that only one
is assigned to each route in order to clarify responsibilities and facilitate supervision.
Implements, tools and clothing
The principal tools and implements for manual sweeping are:
!
sweeper broom (vegetable fibre or plastic);
!
small broom and shovel, used to collect waste and finish sweeping;
!
key for opening drains;
!
hoe for cleaning drains and extracting waste from them.
(1)
(3)
(2)
(4)
(5)
(6)
(7)
(8)
Figure 48 - Modern broom (1), sweeper broom (2), brush (3), small broom (4), key for drains (5),
hoe for cleaning drains (6), shovel (7) and special waste collection pan (8)
Figure 49 - Manual sweeping
132
10. Street cleaning
Clothing can be the same as for most urban cleaning service workers: trousers, t-shirt,
high closing shoes and cap.
For safety reasons the use of reflecting strips on the uniform is recommended,
particularly for nocturnal work.
Sweeper tasks
In general each sweeper should:
!
collect domestic waste discarded in the street (not packaged for collection);
!
sweep the pavement and gutter along the assigned route;
!
empty rubbish bins;
!
weed the gutters and areas around trees and posts (once every 15 days);
!
clean rainwater drains on the route.
Types of sweeping
In spite of the cost, mechanical sweeping is recommended for some situations. A large
mechanical sweeper can sweep an average of 30 km of gutter per shift. As the average
productivity of the manual system is 2km of gutter per worker per shift, a mechanical
sweeper can replace 15 human sweepers.
However the monthly cost of renting a large mechanical sweeper in Latin American and
Caribbean countries can be equivalent to the wages of at least 18 sweepers and taking
into account the importance of job creation for citizens who have received little
education, manual sweeping is in general more appropriate.
Nevertheless there are exceptions, where roads with high volumes of fast moving
traffic, tunnels and bridges represent dangerous situations for manual sweeping. In
such cases it is advisable to consider the possibility of mechanical sweeping.
In tourist areas and city centres small mechanical sweepers can be used as they have a
positive impact on public opinion by demonstrating the efforts made and the resources
invested by the municipality in the urban cleaning sector.
The main mechanical sweepers used are mini-sweepers, mechanical sweepers with
vacuum system; mechanical sweepers without vacuum system; large mechanical
sweepers and mini-vacuums.
133
MINI-SWEEPER
A self-propelled sweeper and vacuum machine with two front brushes and water
sprinkler nozzles to avoid raising dust.
These machines are used for the mechanical sweeping of pavements, squares,
pedestrian ways, etc. In general they provoke curiosity and create public awareness of
the municipality’s efforts to improve and modernize the urban cleaning system.
Figure 50 - Mini-sweeper
MECHANICAL SWEEPER
WITHOUT VACUUM SYSTEM
A medium-sized self-propelled sweeper machine, without vacuum, with a 2.3m³
receptacle, two frontal brushes, one central brush and water sprinkler nozzles to avoid
raising dust.
These machines are used for the mechanical sweeping of roads with fast moving traffic
and represent a good option wherever human sweepers would be in danger of being
run over.
Figure 51 - Mechanical sweeper without vacuum
134
10. Street cleaning
MECHANICAL SWEEPER
WITH VACUUM SYSTEM
A 14ton TGW sweeper machine with a capacity of 6m³ and a vacuum system driven by
an auxiliary engine. It has lateral and central brushes, both driven by hydraulic motors,
and water sprinkler nozzles to avoid raising dust.
LARGE MECHANICAL
SWEEPER
A self-propelled sweeper and vacuum machine with two lateral brushes, one central
brush and water sprinkler nozzles to avoid raising dust.
This machine is used for sweeping tunnels, bridges and large streets with high traffic
volumes. When its waste receptacle is full it can be emptied directly into a dump truck
that operates together with it, thus avoiding having to move the sweeper itself to
empty its load in a transfer station.
Figure 52 - Large mechanical sweeper
MINI-VACUUM
Small vacuum machine that sucks debris through a flexible tube manoeuvred by the
operator. This machine is used for cleaning cycle ways, pavements and parks.
135
Figure 53 - Mini-vacuum
10.3.2 Weeding and scraping services
Where sweeping is not regularly undertaken or rain carries debris onto surfaced streets,
earth can accumulate in gutters and weeds begin to grow.
In such cases weeding and scraping services are necessary to remove earth from the
gutters and re-establish good drainage conditions and the appropriate appearance
of the street.
Figure 54 - Weeding
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10. Street cleaning
In general these services are carried out using very sharp 3½ pound hoes and the
waste is collected using shovels or four pronged pitchforks. When the earth is very
compact hoes or picks are used to scrap it. A scraper is used to deal with mud.
Wheelbarrows, plastic bags, wheelie bins or stationary containers can be used for
waste collection operations.
Rakes can be used to complete weeding and brushes to finish the cleaning. It is
important that drains are cleaned at the same time as weeding and scraping operations
are undertaken, as they tend to become clogged when gutters are covered with
earth and weeds.
When there is a large amount of earth, usually after intense rain in streets close to
slopes, small or big mechanical loaders are used for scraping, depending on the amount
of material and on the type of access and space for manoeuvring.
Figure 55 - Hoe, pick and scraper
Figure 56 - Rake
Types of weeding
Weeding operations can be manual or chemical. The main advantages and disadvantages
of each method are listed below:
Manual
!
uses unqualified labour;
!
is a simple and well known method;
!
involves fewer environmental risks, the main one being erosion processes due to
the inappropriate removal of vegetation;
!
machines and tools are easy to obtain and operate;
!
the operation uses more time;
!
requires large numbers of workers.
137
Chemical
!
the operation uses less time and requires fewer workers;
!
facilitates the removal of vegetation, which quickly dies;
!
when done well, with appropriate techniques and products, it involves few
environmental risks;
!
requires qualified labour;
!
its use is restricted to specific situations and is always an auxiliary to manual weeding;
!
represents a risk to the environment when used without fulfilling technical
requirements;
!
the use of machines and tools involves diverse operating, cleaning and maintenance
techniques.
Planning of weeding operations
The first planning task is to determine the type of weeding: manual or chemical. This
decision depends on the characteristics of each particular area and the more common
method employed is manual weeding.
Chemical weeding uses herbicides and should always be undertaken in compliance
with the producer’s specifications and the relevant legal and environmental restrictions,
and exclusively under the guidance of a specialized professional.
It should only be used as an auxiliary and complementary method side by side with
manual weeding, and when it is adopted regulatory restrictions and requirements should
be rigorously observed as should the instructions on the product labels.
10.3.3 Cutting services
Cutting services are necessary when grass or vegetation is too long and can be carried
out manually or mechanically.
Manual cutting uses tools such as scythes and slicers that can also be used for cutting
tree branches. For the manual cutting of grass a broad scythe is used.
Figure 57 - Scythe, slicer and broad scythe
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10. Street cleaning
Rakes can be used to complete the operation. The manual cutting of grass and other
vegetation with sickles or scythes does not produce good quality results or represent
good productivity (only 100m² per worker per day).
Figure 58 - Manual cutting
Mechanical cutting employs machines such as portable cutters, lateral cutters, tractor
cutters, tractor mounted side-arm cutters and cutters towed by an agricultural tractor.
Portable mechanical cutters that operators carry on their backs and cutters mounted
on small, medium and large tractors are currently available and produce a good quality
result with good productivity.
Portable cutters are suitable for rough land and places that are difficult for larger cutters
to access. One of these machines can cut approximately 800m² per day.
The cutters attached to tractors are appropriate for relatively flat land and can cut
between 2.000 and 3.000m² per day. For cutting operations on the borders of roads
cutters with articulated arms laterally mounted on agricultural tractors can be used.
Figure 59 - Portable cutter (backpack type)
139
Figure 60 - Cutter attached to a tractor
Cut vegetation and the refuse that inevitably appears should ideally be gathered on
the day of the cutting operation using standard or long rakes. Waste can be put in
bags and cut vegetation organized into piles to await collection, which should not be
delayed for more than two days to avoid them catching fire or becoming scattered.
Four to ten pronged pitchforks and long rakes should be used for gathering and
removal operations.
Figure 61 - Long rake and four pronged pitchfork
Mechanical equipment for cutting vegetation
Commonly used mechanical equipment: portable cutter; chainsaw; tractor mounted
side-arm cutter; mini-tractor grass cutter; towed grass cutter and stationary or towed
branch-grinder.
Portable cutter
An approximately 11 kg cutting machine powered by a petrol engine with the rotation
transmitted to the cutting head through a flexible cable. The cutting can be done by a
blade, a disc or a nylon string depending on the type of vegetation. The nylon string is
appropriate for light vegetation and grass and where the machine is used as an edge
cutter, while the toothed disc and the blade are appropriate for thicker vegetation and
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10. Street cleaning
bushes such as guinea grass (Panicum maximum). The machine’s useful life is short,
approximately 2,000 hours, after which maintenance costs are excessively high.
Precautions should be taken to isolate the area surrounding the work site because the
blades, which rotate at high speed, can throw out objects such as small stones from
under the vegetation with the risk of causing injury to people or animals.
Figure 62 - Backpack cutter
Figure 63 - Chainsaw
Chainsaw
A tool powered by a two stroke petrol engine. It is used to prune and cut trees or large
branches, where for example they are likely to fall and cause accidents, principally
after storms and gales.
Tractor mounted side-arm cutter
A hydraulic arm with wheeled head that is mounted on the rear part of a mediumsized agricultural tractor. At the extreme of the arm there is a hydraulically operated
rotating axis blade cutter. It is used to cut large lineal extensions such as roadside
strips and slopes.
Figure 64 - Tractor mounted side-arm cutter
141
Mini-tractor grass cutter
A compact machine on wheels with a central blade. It is appropriate for cutting large
flat and even extensions of grass. This machine does not cut edges but has the
advantage of not throwing out stones or other objects while in use.
Figure 65 - Mini-tractor grass cutter
Towed grass cutter
An implement towed by an agricultural tractor. Its cutting width is up to 1.20m and is
appropriate for relatively flat land. As with the micro-tractor grass cutter, this implement
does not throw out stones or other objects while in use.
Figure 66 - Towed grass cutter
Stationary or towed branch grinder
This machine is powered by a diesel motor. Branches and foliage are fed into the
grinder and the ground material passes through a tube to be deposited in a dump truck
or container. It is used in areas with many trees and bushes where frequent pruning
takes place.
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10. Street cleaning
Figure 67 - Branch grinder
An important rule for mechanical vegetation cutting:
Work should only be undertaken in a screened off area using protective netting to
stop the circulation of people near the area of operations in order to avoid people,
vehicles or objects being hit by stones thrown out by machines. Workers should use
all the recommended IPE (individual protection equipment).
10.3.4 Drain cleaning services
A well functioning street sweeping system significantly reduces the volume of waste
that falls into storm drain inlets or is carried there by rainwater. Consequently the
cleaning of drain inlet boxes is usually assigned to the body responsible for urban
cleaning. As some sweepers may otherwise sweep debris into the drain inlet boxes,
thus slowly clogging them, in general sweepers themselves are responsible for cleaning
them.
The first step of this operation is to remove the covering grill using a drain key. If the
grill is stuck it can be levered out. Where asphalt type material used for repairing the
road surface is partially covering the grill it can be removed with a hammer and chisel
taking care not to break the grill. The same procedures should be followed when
working with any type of rainwater drain.
Waste that has accumulated in drain inlet boxes can be removed using worn hoes,
which are narrower than new ones, grub hoes or special shell shaped tools.
Waste with a low specific weight (leaves and branches) can be put into bags and collected
together with sweeping waste. Earth extracted from drains should be collected by
dump trucks.
143
(1)
(2)
(4)
(3)
Figure 68 - Clogged drain
Figure 69 - Lever (1), hammer (2), chisel (3)
and drain key (4)
Drain inlet boxes can also be cleaned using special machines with suction hoses (VacAll type) or sweepers with vacuum suction equipment.
The cleaning of the rainwater drainage network is done with special machines through
points of access to the drainage system.
Figure 70 - Pumping truck
A pumping truck is used in urban and industrial operations for cleaning drain boxes,
drain accesses, septic tanks, separated chambers and sewers. Waste is pumped through
a four inch diameter hose and the most commonly used models have a capacity of 6, 7
or 8m³ corresponding to a truck TGW of 12, 14 or 16 tons respectively.
Mechanical sweepers with suction systems usually have tubes appropriate for drain
cleaning.
The cleaning of drain inlet boxes in areas that are susceptible to flooding in the event
of heavy rain should be regarded as a priority.
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10. Street cleaning
10.3.5 Market cleaning services
In most Latin American and Caribbean countries there are informal public street markets
set up particularly for the sale of vegetables, fruit, fish and other types of food. Many
people go to them and generate large amounts of waste.
It is therefore necessary to plan appropriate cleaning services in order to keep the
markets clean from the moment they begin functioning until the stalls are dismantled.
Market cleaning is done manually and the size of teams should correspond to the size
of the market, i.e. the number of stalls and the number of people visiting it.
Independently of the market cleaning services that it provides, the Municipality should
take firm measures to ensure that stall operators themselves avoid waste being
discarded in the street and install receptacles to store waste by their own stalls.
While large markets are functioning workers can be collecting waste produced by stall
owners and their customers by circulating with manual collection carts lined with large
plastic bags. When full these bags can be kept at a storage point adjacent to the
market in a location chosen to incur the minimum possible nuisance to the public and
facilitate collection by the collection vehicle.
Where possible 240 litre plastic containers with lid and wheels should be used to store
waste produced while the market is operating. Special attention should be given to
stalls selling fish, chicken and pork products.
Figure 71 - Containers located close to a market
When the market is dismantled a larger team of between four and eight workers
sweeps and cleans the area. For this task sweeper brooms are used together with
shovels and brushes for collecting the waste. In some cities large wooden squeegees
are used as an auxiliary tool. Waste is collected by a compactor truck or a dumpster
carrier truck.
145
Once it has been swept the street should be washed by a street washing truck with
a pressure water jet, paying particular attention to areas around fish stalls sites,
which, along with the drains, should be washed with disinfectant and deodorant
products.
(1)
(2)
(3)
(4)
Figure 72 - Sweeper broom (1), brush (2), wooden squeegee (3)
and shovel (4) used in market cleaning
10.3.6 Manual and mechanical waste removal services
In many cities with large wasteland areas refuse is often irregularly discarded there.
Open wastelands and uncared for public areas, in combination with inadequate urban
cleaning systems, generate what are called “waste accumulation sites”.
The accumulation often begins with construction rubble being dumped and, as “rubbish
attracts rubbish”, this is followed by the addition of pruned vegetation, old tyres, the
remains of packaging, and organic waste. Later weeds start to grow and the entire
scenario results in blocked drains and serious sanitary and environmental consequences.
To deal with this type of problem cleaning services should establish a specific
operational methodology as these situations involve not only clearing activities (weeding
and vegetation cutting) but also the removal of all types of waste that have accumulated
on such sites. This work requires machines and tools appropriate for each type of
waste, not only for clearing tasks but also for collection and transport to the final
destination, all of which places an additional burden on the system through higher
operational costs due to the extra personnel and machines required in these cases.
This type of activity is commonly called waste removal and can be manual or
mechanical.
The removal of unpackaged refuse such as common waste, soil and rubble can be
done manually with shovels, lifting it directly into the box of a dump truck or into
metal containers that will later be removed by appropriate trucks with cranes. To
remove cut vegetation a four pronged fork is used. A three or four pronged pitchfork
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10. Street cleaning
is used to separate the pile of accumulated waste in order to facilitate its handling
and transport.
In cases where there is a large amount of waste and especially where a lot of soil or
rubble has to be removed the use of a wheeled front loader (mechanical loader) is
recommended.
Figure 73 - Mechanical loader at work
Figure 74 - Three pronged pitchfork
10.3.7 Beach cleaning services
Sandy beaches have to be kept clean by the application of various complementary
measures.
The first and most important of these is to reduce the amount of waste that gets onto
the beach by installing rubbish bins both on the beach itself and on pavements that
border it so that people can deposit waste in them. Each summer, awareness raising
campaigns should be initiated to promote the use of rubbish bins for waste generated
on the beach. Where it is not possible to install purpose made rubbish bins, alternative
structures for depositing waste can be used such as setting vertical concrete pipe
sections on the beach lined with plastic bags.
Once these basic measures have been adopted, the planning of services should involve
the following principal elements:
!
the frequency of beach cleaning operations should be organized with a view to the
beach always being as clean as possible and in good condition for use by citizens;
!
the timing of operations should be compatible with beach activities so as not to
inconvenience users;
!
labour requirements are calculated according to the surface area to be maintained,
the required frequency of operations and productivity rates determined by field
measurements;
147
!
service organization can be based on defined sectors or on the entire extension of
the relevant beach.
Beach cleaning services can involve both manual and mechanical operations.
The manual cleaning of the beach surface should ideally be done at the end of every
sunny day using wire rakes (usually having 20 to 25 prongs with a 1cm gap between
them), ten pronged pitchforks and plastic net sieves, as well as plastic bags and
containers for carrying the waste to the compaction vehicle or dump truck that
accompanies the team as it progresses.
The labour productivity rate varies depending on diverse factors such as user behaviour
and the availability of rubbish bins. An average of 1.000m² per hour per worker can be
taken as an initial base value.
(1)
(2)
(5)
(3)
(4)
Figure 75 - Wire rake (1), plastic net sieve (2), ten pronged pitchfork (3), concrete pipe section
with plastic bag (4) and container (5)
Figure 76 - Waste containers
Figure 77 - Manual removal of beach waste
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10. Street cleaning
Figure 78 - Transfer of beach waste from a
tractor drawn trailer to a truck
Figure 79 - Manual beach cleaning
Mechanical cleaning is appropriate for beaches with large amounts of waste and big
extensions of sand. In these cases purpose built machines towed by agricultural tractors
are used and have a productivity of approximately 10,000m² per hour. This type of
cleaning collects large and medium-sized waste but leaves ice cream sticks, straws,
cigarette ends and food remains.
On very wide beaches (where there is more than 30 metres of sand between the
water and the land), four wheel drive agricultural tractors with trailers can be used to
accompany the cleaning team as they progress along the beach and transport waste to
a truck similarly progressing along the street bordering the beach.
In out of season periods beaches should be cleaned with machines that stir the sand,
pass it through a vibratory sieve in order to catch smaller objects and produce a
bactericidal effect by exposing lower layers of sand to sunlight. Beach cleaning machines
towed by four wheel drive mini-tractors with a maximum potency of 60hp are used.
The operation of this machine is entirely mechanical. Sand is taken from a maximum
depth of 20cm, sieved, aired and returned to the beach. The type of net used in the
sieve varies according to the characteristics of the beach.
Figure 80 - Mechanical beach cleaning
149
An option that may be considered for very crowded beaches is to replace sand above
the tide line with sand from below it that has been washed by the sea and is therefore
cleaner. Such an operation should be carried out using tractor-bulldozers and mechanical
loaders after an environmental study has been undertaken by specialists.
10.4
How to reduce street waste
The amount of solid waste in streets can be reduced through:
!
smooth surfaces and appropriate inclination for streets, gutters and pavements;
!
appropriate dimensions and maintenance for rainwater drainage systems;
Figure 81 - Smooth pavements and gutters
facilitate cleaning
Figure 82 - Uneven gutters make cleaning
difficult
!
planting tree species in combinations that do not result in abundant leaf fallings
several times a year;
!
instalment of rubbish bins in streets with high pedestrian concentrations, on corners,
at bus stops and in front of bars, cafes and supermarkets;
Figure 83 - Rubbish bins
150
10. Street cleaning
!
regular sweeping and waste removal from waste accumulation sites (“rubbish attracts
rubbish” while “cleanliness promotes cleanliness”);
!
public awareness raising campaigns related to the maintenance of cleanliness;
!
establishment of legal devices that sanction citizens who disobey urban cleaning
regulations.
As can be seen, urban cleaning issues are related to various aspects of public urban
works and should be taken into account by the respective municipal bodies when
urban improvement projects are being planned.
Figure 84 - A dirty square
The dirty and uncared for appearance of the square is added to by so-called “white
waste”, made up of papers, plastic and packaging.
In general it can be observed that in well cared for and well maintained streets passersby are more conscious of cleanliness and discard less rubbish on the ground.
Commercial establishments should not be allowed to sweep their waste onto the
street. Those who persist in doing so should be fined and for this the municipality
needs to have a good supervision system.
(Figure 85)
Figure 85 –
Figure 85 - Waste being swept into the street
151
10.5
Street cleaning in tourist cities
As is the case with domestic waste collection, an influx of tourists to a city causes
considerable problems for the street cleaning service, principally in regard to sweeping
and, in the case of coastal cities, beach cleaning.
An underlying cause of these problems is the temporary population increase and the
resultant increase in demand for public services. A good example is the increase in
the number of people circulating through the streets and the consequent generation
of waste in different quantities and at different times than those in the normal routine
of the city.
Another aspect that creates difficulties for cleaning services is that in general tourists
are not acquainted with the operational routine of cleaning in the city and many times
they do not do what they should as users to cooperate with the body providing the
service.
There are also cultural and behavioural questions with some tourists who take the
view that as it is not their city they are not interested in keeping it clean. They discard
rubbish indiscriminately and fail to comply with behavioural norms and regulations. These
however are the same tourists who will not return to the city if they consider it dirty or
not well cared for.
In regard to sweeping, the measures that have to be implemented to maintain required
levels of street cleanliness are:
!
increase the hours of work shifts (overtime) on some sweeping routes in order to
respond to the greater seasonal demand for services, taking into account the limits
imposed by employment legislation;
!
restructure existing routes increasing the number of sweeping shifts and contracting
extra workers on a temporary basis.
Figure 86 - “Molok” type container in use
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10. Street cleaning
It is also important to increase the numbers and maintenance of containers and rubbish
bins strategically positioned in streets, squares and other public spaces to facilitate
appropriate waste disposal. The aesthetics of these units and their integration with
the landscape should be taken into account.
In the case of coastal tourist cities the problems are more difficult to solve as, with
few exceptions, they do not maintain teams exclusively for beach cleaning services,
which are complex, difficult to mechanize and relatively labour intensive. For an effective
provision of this service during the tourist season the most appropriate course of
action may be to contract a separate team to undertake the cleaning of the beach and
its bordering seafront, and equip it with all the tools necessary to carry out this service.
Extending work shifts and giving seasonal tasks to workers who normally perform
other activities is in general neither feasible nor sufficient to solve the problem
completely.
One general administrative measure that a municipality can take to reduce problems
faced by the urban cleaning sector during the high tourist season is to schedule
employees’ holidays for the months of the low season so that during periods when
demand for services is at its greatest the entire staff is available.
An ongoing awareness raising campaign can be run throughout the high tourist season
with the participation of companies that benefit from tourism, such as hotels, restaurants
and entertainment establishments. The campaign should encourage people to take
better care of the city and guide visitors to cooperate in maintaining hygienic conditions
and cleanliness in the streets. Such a campaign can and should be directed to the
entire city but may concentrate more on neighbourhoods associated with tourism and
along the seashore where applicable.
153
11
154
Recovery of recyclable materials
11. Recovery of recyclable materials
11.1 Concept
With the growing prominence of environmental conservation policies citizens are
becoming increasingly concerned about solid waste issues. The increased per capita
waste generation, fruit of capitalist society’s high consumption model, not only
concerns environmentalists but also governments and the general public. This concern
with waste issues is due both to the potential for contamination and the continuous
need to find new final disposal sites, not to mention the negative impacts caused by
an irrational consumption of non-renewable natural resources.
On an international level these issues have prompted a debate about the consumption
habits of societies and the responsibility of companies, resulting in what is known as
4Rs practice (Reduce, Reuse, Recycle and Recover). This concept establishes the
principle of waste generation prevention, taking as its departure point reduction.
That is, a reorientation of consumers’ needs and purchasing preferences, and
therefore of companies’ production, favouring products that are less damaging to
the environment and avoid wastage. In spite of the integral nature and order of the
4Rs, recycling is the one that provokes most public interest principally due to its
clear claims to environmental benefits.
4 Rs practice:
reduce – aimed at diminishing the amount of disposable packaging and containers,
through a change in consumption habits. The reorientation of consumers’ preferences,
favouring products with more durability and less packaging, putting pressure on producing
companies to use the least amount of packaging possible.
reuse – the reuse of a material or product without changing its shape or original nature.
Different types of waste can be reused such as bottles, newspapers, magazines, books
and other products.
recycle – the transformation of materials into raw material for production processes.
This process requires the segregation of waste at source, in transfer stations or at
final disposal sites. One of the most important incentives for recycling is the saving of
energy and natural resources.
recover – principally related to appropriate waste incineration processes that produce
energy and consequently conserve fossil fuels.
Reduce, the less waste the better;
Reuse, maximize or diversify the use of a given consumer product;
Recycle, a positive contribution where reduce and reuse are not applicable;
Recover, mostly associated with energy generation.
155
11.2 Selective collection programs
A significant role can be played by educational programs that promote 4Rs practice
and foster the development of environmental awareness amongst citizens. These
programs, for the most part related to pre-recycling waste segregation, can become
instruments for income and employment generation, particularly in less developed
countries.
This aspect has a significant relevance to many Latin American and Caribbean cities
where social crises have resulted in large numbers of people turning to refuse
segregation as a means of survival through the commercialization of recyclable materials,
almost always in extremely precarious conditions.
The principal benefits of recycling discarded materials (plastic, paper, metal and glass)
are:
!
the saving of non-renewable raw materials;
!
the saving of energy in production processes;
!
the prolongation of sanitary landfills’ useful life;
!
the generation of income and employment.
The great challenge in implementing selective collection programs is to find a model
that is in itself economically sustainable. Traditional models applied in developed
countries almost always involve public subsidies and are difficult to apply in developing
countries. However the social and environmental benefits of these programs also have
to be considered.
In practice, a model involving the selective collection of materials at the source of
generation (houses, offices, shops and factories) and associated with a program of
income and employment generation, is the one most applied in Latin American and
Caribbean cities.
A scarcity of resources often hinders the implementation of such programs but some
municipalities are endeavouring to promote alternative models adapted to fit their
particular economic circumstances.
For example, where large parts of the population live in poor socioeconomic conditions
projects can be established that involve the “bartering” of recyclable materials for
food and an increased level of community participation.
Another example is the establishment of partnerships between public authorities and
civil organizations, such as segregator cooperatives, in which the latter undertake the
collection of materials.
156
11. Recovery of recyclable materials
Amongst the options available for the segregation of recyclable materials at the source
of generation are:
!
selective door to door collection;
!
voluntary drop-off centres;
!
segregator organizations.
11.2.1 Selective door to door collection
The most commonly used model for selective collection programs is the segregation by
residents of discarded recyclable materials, which are then collected by specialized vehicles
from each housing unit, in a similar way to conventional domestic waste collection.
Figure 87 – Selective collection by compactor truck
Figure 88 – Selective collection by truck without compaction
The separation of recyclable materials in households can be done in two ways:
identifying and separating different types of recyclable material and storing them in
separate containers, or putting all recyclable materials in one container.
157
The system in which different types of recyclable materials are separated requires
more space for keeping the containers, one for each type of recyclable material, which
makes it more difficult in apartments or small houses. This model also requires a
collection truck with a box divided into compartments to transport materials separately.
With the other more commonly used model residents separate domestic waste into
two categories:
!
organic material (damp) – including the remains of food and non-recyclable materials
that are stored in a container for this category and are collected by the normal
domestic waste collection service;
!
recyclable materials (dry) – paper, metal, glass and plastic, which are stored in a
container for this category and are collected by the selective collection service.
In most cities where the system is operated, door to door selective collection can be
made once a week using open box trucks. The relatively long interval between selective
collections is possible because of the inert nature of recyclable materials.
Once collected, recyclable materials should be transported to a segregation plant,
generally equipped with tables, where materials are separated by type in preparation
for their commercialization.
Segregation plants should also have presses so that materials with a lower specific
weight (paper and plastic) can be baled to facilitate storage and transport.
Figure 89 – Recyclables segregation plant
It is important that the public is clearly informed of the correct criteria for the separation
of materials for commercialization in order to avoid the expense incurred with
transporting and handling non-recyclable waste at the segregation plant.
The principal disadvantages of door to door selective collection are the increased
transport costs involved in the need for extra collection trucks and the high unitary
cost of collection compared with conventional collection.
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11. Recovery of recyclable materials
Both before and after the initiation of selective collection services the public authority
should continuously encourage citizen participation through promotional campaigns
and environmental education. Consequently planning for a project has to allow for
the necessary resources to run such campaigns, which are fundamental to maintaining
citizen participation levels.
Selective collection is not profitable when the municipality uses its own vehicles,
labour and structure. Ideally it should standardize, regulate and foster the process
without participating directly in its operation. As an incentive it could invest in
warehouses and equipment such as bale-presses, grinders, washers, etc. to add value
to the recyclable material.
A selective collection system in which a municipality does not directly participate but
establishes alliances with the community for operating it, results in significant economic
benefits for the urban cleaning system as previously segregated recyclable materials
will not need to be collected, transported and disposed of in a landfill, all of which
reduces the costs and work of the municipality.
11.2.2 Voluntary Drop-off Centres (VDC)
Containers sited in public places for the public to voluntarily deposit pre-segregated
recyclable waste.
The responsible public body usually standardizes the program to facilitate organization
and community participation. It can for example define a colour code for the different
types of waste, which will then be used for identifying containers and collection
trucks, as well as in waste segregation educational campaigns. See the suggestions in
table 15.
Table 15
Colour code for recyclable solid waste
Container colour
Recyclable material
Blue
Paper and Cardboard
Red
Plastic
Green
Glass
Yellow
Metal
Brown
Organic waste
Source: CONAMA resolution Nº 275 of 25/4/2001 (Brazil)
159
VDCs can be set up in partnership with private companies that can for example finance
their installation in return for the use of the site for advertisements.
Some municipalities are establishing partnerships with recycling companies that finance
both the installation of containers and the collection of materials deposited in them.
The establishment of VDCs in tourist areas should take into account potential
communication problems with the labelling of containers. To overcome the language
problem it is recommended that images are used to indicate the correct storage
container for each type of recyclable material.
Here too it is important to regularly empty VDC containers in order to avoid irregular
waste accumulation on the site.
Figure 90 - Special containers for a VDC
Figure 91 - Examples of VDCs
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11. Recovery of recyclable materials
11.2.3 Segregator organizations
The appearance of numerous segregator organizations in Latin America and the
Caribbean during recent decades reflects not only the socioeconomic crises that many
of these countries have experienced but also segregators’ capacity for articulation
and organization, which though still incipient has nevertheless grown significantly 4.
In spite of advances, working conditions for most segregators are still very precarious
and many of them continue to work without any support or acknowledgement.
Improvements in this sector’s working conditions depend to a large degree on several
institutions having an articulated vision and commitment that leads to the formulation
and implementation of effective public policies.
Many municipalities, in an effort to include a social dimension in their selective collection
programs or pressed by groups of segregators themselves, establish some type of
agreement or partnership with segregator cooperatives that then undertake the
collection and separation of discarded recyclable materials.
The principal advantages of working with segregator organizations are:
!
the generation of income and employment;
!
the social inclusion of segregators (who mostly live in the streets) as citizens;
!
a reduction in the costs of selective collection programs;
!
the organization of segregators’ work to avoid untidiness in waste collection and
the storage of materials in the streets;
!
a reduction in the costs of the city’s urban cleaning system due to the collection of
part of the waste by segregators leaving less waste for collection, transportation
and final disposal.
Such savings on costs should benefit segregator organizations in the form of investment
in uniforms and infrastructure (warehouses for segregation and storage, standardized
carts, presses, bale lifters) so that the segregated materials increase in value in the
recyclables market.
It is important that municipalities adopting this model offer institutional support to
segregator organizations, principally in regard to granting the use of physical space,
providing juridical and administrative assistance for legalization processes and, as has
already been mentioned, providing basic equipment such as bale-presses, carts, etc.
Assistance should also be provided for the training of organization members to promote
greater autonomy.
One of the main factors that fosters the strengthening and success of segregator
organizations is the profitable commercialization of recyclable materials. The less
4.
Segregators from several Latin American countries met to define common strategies at the first and second Latin
American Congress of Recyclable Material Segregators, held in Brazil in 2003 and 2005.
161
intermediaries that are involved in the process between the segregator organizations
and the final consumer (the recycling industry) the higher the sale price will be. The
following basic conditions should be met:
!
good quality material (sorted by type of material, with a low impurity content and
appropriate packaging or baling);
!
ample scale of production and storage: the larger the production and the quantity
available to the buyer, the better the selling conditions;
!
regular production and delivery to the final consumer.
These conditions are rarely achieved by small groups but the organization of joint
commercialization centres is an option that creates better conditions for direct
negotiations with recycling companies.
When a public authority enters into partnership with a segregator organization it is
important that it continues to offer institutional support for the provision of basic
needs, the lack of which would hinder efficient performance, especially when
operations are beginning to be established.
Amongst the measures that should be taken in support of segregator organizations are:
!
administrative and accounting support, the contracting of a professional specialized
in management to train the group;
!
implementation of a social assistance program for segregators and their children;
!
provision of uniforms and individual protection equipment;
!
implementation of literacy courses and training for segregators;
!
implementation of rehabilitation programs for those with a dependency on chemical
substances;
!
implementation of environmental education programs for segregators.
Figure 92 – Segregators from a cooperative working in the street
162
11. Recovery of recyclable materials
Taking into account the lack of experience of those running the organizations, the
public authority can, during the initial phase, also help with the commercialization of
recyclable materials. For the eventuality of difficulties related to fluctuations in the
buying market, it is recommended that the group has a small liquid capital so that
segregators’ minimum incomes are guaranteed until better commercialization conditions
are re-established.
All these initiatives and types of support should be applied with a view to eventual
sustainability, that is, it is important that the strengthening of the segregator groups
leads in the long term to them gaining more autonomy and independence in their
activities.
163
12
164
Solid waste treatment
12. Solid waste treatment
12.1
Concept
Between collection and final disposal municipal solid waste can be subject to
processes that produce technical-operational, economic and sanitary benefits. These
processes, known as waste treatment, contribute to human and environmental
protection.
The objectives of solid waste treatment are to reduce its volume and to lower its
contaminating potential by transforming it into inert or biologically stable material.
Processes applied to solid waste can be mechanical, thermal or biological.
Mechanical
!
classification – sorting by economic criteria or as a preparatory step for subsequent
processing;
!
grinding – reduces the granulometry and volume of waste as well as mixing and
homogenizing it;
!
compaction – reduces empty spaces (increases waste density).
Thermal
!
incineration – controlled burning at high temperature in purpose built equipment
with environmental control devices;
!
pyrolysis – thermally induced waste degradation in the absence, or limited presence,
of oxygen at a lower temperature than that involved in incineration, producing high
energy liquids and gases and less atmospheric contamination.
Biological
!
aerobic – stabilization and composting processes that principally generate water,
carbon dioxide and heat;
!
anaerobic – important for the production of methane. Waste degradation is slower
and generates fatty acids, acetic acid, other acids of low molecular weight and some
unpleasantly smelling toxic gases such as sulfhidric acid (H2S).
The most effective treatment is applied by the general public when
they take action to reduce the amount of solid waste by avoiding
wastage, reusing materials, separating recyclable material at source
and appropriately disposing of waste.
165
12.2
Domestic solid waste treatment
12.2.1 Recycling
The recycling process comprises: the segregation of materials
such as paper, plastic, glass and metal from domestic solid waste,
their sale to specialized companies and their transformation into
material for producing goods that can be sold in the consumer
market.
Recycling offers the following advantages:
!
conservation of natural resources;
!
energy saving;
!
economies in solid waste transport costs and in the occupation of landfills (as the
amount of waste to be transported to the landfill is reduced);
!
generation of income and employment;
!
greater public awareness of social and environmental problems.
The ideal recycling system begins with the separation of solid waste in homes so that
only potentially recyclable materials are sent to segregation plants. Such prior separation
reduces the amount of contamination affecting materials and in consequence increases
the productivity of segregation plants.
Recyclable material segregated from mixed solid waste is dirty and contaminated, so its
processing is more complicated and expensive.
Recyclable material contained in general domestic solid waste can be separated in the
segregation plant through manual or electromechanical processes that in terms of weight
usually yield only 3% to 6%, depending on the plant’s size and degree of sophistication.
The high cost of recyclable material transformation processes has resulted in many
recycling companies not following environmental guidelines stipulating the use of clean
(but expensive) technologies. If the necessary precautions are not taken recyclable
material transformation processes can be extremely harmful to the environment. In
such a case, the outcome is much worse than if the waste had been disposed of in a
sanitary landfill, together with the rest of the domestic waste, where it would be subject
to more rigorous environmental controls.
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12. Solid waste treatment
After the segregation of recyclable material that can be used for production, the rest
of the domestic waste, which is fundamentally organic, can be processed to obtain
compost for agricultural use. This subject is dealt with in the next section.
The gravimetric values (in weight) of the different types of solid waste after processing
in a segregation plant with a composting unit, and their uses, are in general as expressed
in the following flow chart of a hypothetical plant with an intake capacity of 1,500kg/
day (see figure 93). It can be seen that, provided there is compost production, from
the total amount of waste that arrives for processing only 12.6% needs to be transported
to the final disposal site. This material is inert and therefore not contaminating because
the residual organic content has been stabilized with most of the organic matter being
transformed into compost.
Domestic
waste collection
189kg/day (12.6%)
Landfill
Refuse
Grinding of the
predominantly
organic fraction
60kg/day
(humidity
loss 4%)
Selection
table
Pre-selection
of bulky objects
225kg/day (15%)
Recyclable
materials
Compost
curing piles
Refuse
Reception
Recoverable
materials
Loss of matter
heat+CO +water
Storage of composted
ground material
Sieving
Organic
preparation
(compost)
456kg/day (30.4%)
Figure 93 - Flow chart of the process and mass fraction proportions
These percentages however are based on the optimum operational performance
conditions for a segregation and composting plant, which are:
!
small-sized unit (low quantity of waste to be processed) which facilitates maximum
efficiency of manual segregation;
!
reception of domestic waste from differentiated collections, thus avoiding a mixture
of recyclable and non-recyclable waste and reducing the percentage of nonrecoverable waste;
!
existence of a strong and diversified market for recyclable materials so that the
commercialization of a wide range of materials is possible, thus reducing the amount
of non-recoverable waste.
167
In the case of bigger recycling and composting units (in large cities) the level of recyclable
material recovery tends to be less and the amount of disposable material for treatment
greater, which results in a larger percentage of non recyclable waste at the end of the
process.
As in practice optimum conditions rarely exist, the average production of nonrecoverable waste in recycling and composting plants can be estimated as 25% of the
total weight of refuse processed there.
Clearly this proportion depends on the composition of the domestic solid waste
generated in each city, which can be affected by local particularities, as mentioned in
chapter 5.
The operation of a segregation and composting plant is divided into three stages: reception, feeding and selection.
Reception
Here collection trucks unload domestic solid waste and the following processes are
applied in sequence:
!
determination of the volume or of the weight using a weighbridge, or in smaller
establishments by means of estimative calculations;
!
storage of unloaded waste in silos or warehouses of a size compatible with the
daily processing capacity.
Feeding
The loading of waste onto the processing line by means of machines such as loaders,
overhead cranes, or hydraulic arm grabs. In smaller plants feeding can be manual.
In bigger establishments devices can be used to enable trucks to unload solid waste
directly onto the processing lines, thus freeing the operation of the processing lines
from dependence on the functioning of feeding equipment.
Selection
In this sector the flow of waste on the selection lines is regulated and segregation by
type of recyclable material is carried out.
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12. Solid waste treatment
Equipment used for flow regulation comprises metal conveyor belts and mixer drums.
The latter are appropriate for plants with a maximum capacity of 10tons per hour
per line.
The selection conveyor belt speed should be 10 to 12m/min, to allow sufficient time
for the manual separation of materials by the segregators.
Segregators are stationed along the selection belt next to channels or containers. The
ones near the beginning of the conveyor belt separate larger objects (paper, cardboard
and sheet plastic) so that smaller objects (aluminium cans, glass containers, etc.) can
be seen and separated by segregators nearer to the end of the line. In general, the
first position on the selection line is occupied by a worker who breaks open bags and
scatters their contents across the width of the belt in order to facilitate the work of
the other segregators.
In establishments that have several parallel selection belts they should be installed on
a level that is high enough to allow for a level below them where baling presses can
operate and there should be enough space available for moving segregated materials.
The distinct selection processes can be set up independently of each other or be
interconnected. In general simple plants only have selection conveyor belts, while more
complete ones use other equipment that itself removes recyclable materials or assists
manual segregation. Examples of auxiliary equipment are: sieves, ballistic separators,
magnetic separators and pneumatic separators.
In plants that process up to 10tons/day, instead of a selection belt, a concrete table
can be used that should be slightly inclined and have raised lateral borders to avoid the
fall of waste. Waste is manually pushed along the table by segregators using small
planks as recyclable materials are withdrawn. In this type of plant the waste that arrives
from collection is unloaded close to the end of the selection table and is transferred
to the table by a worker with a pitchfork or another appropriate tool.
Figure 94 - Manual selection in a small capacity recycling plant
169
Large capacity recycling plants need to use a high level of mechanization for feeding
and the movement of the large volumes of waste along the operational lines.
Figure 95 - Manual selection in a large capacity recycling plant
The type of recyclable material that will be separated in a segregation plant depends
above all on demand from the industry. However in most plants the following materials
are segregated:
!
paper and cardboard;
!
hard plastic (PVC, HDPE, PET);
!
sheet plastic (low density polyethylene);
!
entire bottles;
!
transparent glass, coloured glass, mixed glass;
!
ferrous metal (cans, sheet metal, etc.);
!
non-ferrous metal (aluminium cans, lead, antimony, etc.).
It is important to note that a segregation plant can only operate if the urban cleaning
system of the city includes the selective collection of hazardous waste, such as medical
waste. It is essential that this type of material does not arrive at the segregation plant
in order to avoid endangering workers who handle the waste. Street sweeping waste
and construction rubble should also not be brought to the segregation plant as they
contain materials that can damage the machines.
12.2.2 Composting
Composting is the natural biological degradation of organic materials (with carbon in
their structure) of animal or vegetable origin through the action of micro organisms. It
170
12. Solid waste treatment
is not necessary to add any type of substance, including chemical substance, to the
mass of organic domestic waste for composting to take place.
Composting can be aerobic or anaerobic, depending on the presence or absence of
oxygen in the process.
In anaerobic composting, degradation is caused by micro organisms that live in
environments without oxygen; it takes place at relatively low temperatures, emits a
strong unpleasant odour and requires more time for the organic matter to stabilize.
In aerobic composting, the more appropriate treatment for domestic waste,
degradation is caused by micro organisms that only live in environments containing
oxygen. Temperatures can reach 70ºC, odours are not unpleasant and degradation is
quicker.
The final product of an organic waste aerobic composting process is compost, a material
rich in hummus and mineral nutrients that can be used in agriculture to improve soil
quality and as a fertilizer.
Hummus is a completely bio-stabilized homogeneous organic substance,
dark in colour and high in colloidal particle content that when applied to
soil improves its physical characteristics for agriculture.
Stages of composting
The aerobic composting process can be divided into two stages.
The first stage, bio-stabilization, involves a significant increase in the temperature
of the organic mass, reaching 65ºC and later stabilizing at the ambient temperature
towards the end of the cycle, which in natural composting systems takes
approximately 60 days.
The second stage, maturing, takes another 30 days. In this stage the humidification and
mineralization of the organic matter takes place.
Factors that influence composting
A sufficient quantity of the micro organisms necessary for degrading organic matter
is inherently present in domestic waste. If humidity and airing are appropriately
controlled these micro-organisms proliferate quickly and homogeneously throughout
the mass of waste.
The waste also contains pathogenic micro organisms such as salmonella and streptococcus.
These pathogenic agents are eliminated by the heat generated in the biological process
as they do not survive temperatures in excess of 55ºC for more than 24 hours.
Structurally the micro organisms that degrade the organic matter are approximately
90% water, therefore the water content has to be controlled during the process.
171
In aerobic composting the metabolism of the micro organisms needs oxygen. Factors
such as humidity, temperature and granulometry influence the availability of oxygen. A
lack of oxygen produces unpleasant odours.
Compost is aired by stirring the material with mechanical loaders or special machines.
In small units it can be stirred manually with pitchforks or other tools.
During the aerobic stage the more the matter is exposed to oxygen, the quicker the
degradation. In addition, the smaller the particles, the greater the surface area that is
exposed to oxygen and therefore the shorter the composting process. However, if
particles are too small an excessively compacted mass can result, which makes the
airing process more difficult.
Simple composting plants
Simple plants make compost naturally in the open air. In such plants the waste is
fragmented in a hammer-mill and then “piles” are set. The organic matter remains there
until its bio-stabilization and is stirred with a predetermined frequency (for example,
on the third day after the formation of the pile, and from then on, every 10 days until
completing 60 days). Once it is biologically stable the material is refined in a sieve and
is ready to be used in the preparation of agricultural soils.
The surface of the area where piles are set in a composting plant should be smooth,
well compacted and if possible surfaced, with enough of a slope (2%) for rainwater
and leachates produced in the composting process to run off. These effluents, which
in well managed piles are produced in very small quantities, should be sanitarily treated
in stabilization ponds.
When designing the composting area sufficient space has to be planned for between
the piles so that trucks, mechanical loaders and special machines for stirring the piles
can circulate. Sufficient space for the storage of compost that is ready for use should
also be made available.
Composting piles should have a pyramidal or conical shape, with bases of up to 3m per
side or 2m diameter and be no more than 1.50m to 2m in height.
Figure 96 - Aerobic composting in a small capacity plant
172
12. Solid waste treatment
Figure 97 - Aerobic composting in a large capacity plant
If the height of the piles is more than 2m it is difficult to stir and air the organic mass.
A conical form facilitates the running off of rainwater and avoids the pile becoming
saturated.
Characteristics of compost
The principal characteristic of compost produced by domestic waste composting is
the presence of hummus and mineral nutrients, the amounts of which determine the
quality of the compost.
Hummus makes soil more porous thus facilitating the airing of roots and the retention
of water and nutrients. Mineral nutrients can comprise up to 6% of the weight of the
compost and include nitrogen, phosphorus, potassium, calcium, magnesium and iron,
which are absorbed by plant roots.
Compost can be used for any type of cultivation, whether or not chemical fertilizers
are being used. It can be used to correct soil acidity and rehabilitate eroded areas.
Compost quality
In general compost quality is standardized on the basis of parameters established by public
institutions in each country with a view to ensuring its effective application in agriculture.
In Brazil, for example, commercialized compost produced by domestic waste composting
plants must comply with minimum values established by the Ministry of Agriculture.
These values are presented in table 16 as a reference.
Table 16
Values established in Brazil for commercialized compost
Parameter
Value
Margin
Organic matter
> 40%
- 10%
Total Nitrogen
> 1.0%
- 10%
Humidity
< 40%
+ 10%
C/N relation
< 18/1
PH
> 6.0
21/1
- 10%
173
Compost must be periodically subject to physical and chemical analysis in order to
verify its compliance with the minimum quality standards established by the relevant
governmental body.
One of the main concerns of compost users is the presence of heavy metals in sufficient
concentrations to be prejudicial for cultivation and/or produce consumers. Some
components of domestic waste such as coloured paper, textiles, rubber, ceramics and
batteries contain heavy metals. Composting plants’ segregation operations must remove
these materials as much as is possible from the waste that is received.
In most Latin American and Caribbean cities, especially in small and medium-sized ones,
it is unlikely that compost produced from domestic waste will contain a concerning
level of heavy metals because of the socioeconomic characteristics of most of the
population and therefore the type of waste generated.
12.2.3 Choosing a treatment option
Segregation and/or composting plants are alternatives that municipalities should consider
when planning the treatment of domestic solid waste that they collect.
However, before proceeding they should examine the practicalities of the following
required conditions:
!
existence of a reasonably efficient and regular collection system;
!
existence of selective collection for domestic, public and medical waste;
!
existence of a market for recyclables and compost in the region;
!
availability of sufficient space to establish a segregation plant and/or composting
area;
!
availability of resources to finance initial investment;
!
availability of personnel with sufficient technical training to select appropriate
technology, supervise the setting up of a plant, maintain machines and supervise
their operation.
When determining which machines to install it should always be taken into account
that the more sophisticated and automatic they are, the higher the initial investment
and maintenance costs and the lower the level of employment generation.
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12. Solid waste treatment
In Latin American and Caribbean countries, where there is high unemployment, labour
intensive systems are recommended such as manual segregation plants.
A considered economic feasibility study of any proposed project should be undertaken
taking into account on the one hand the advantages of installing a plant (reduction of
the amount of waste to be transported and buried, sale of compost and recyclable
material, generation of incomes and employment, environmental benefits), and on the
other, the implementation, operational and maintenance costs.
ECONOMIC
FEASIBILITY STUDIES
Prior to the establishment of a segregation or composting plant an economic feasibility
study should be carried out covering the following points:
Investment
!
environmental licenses;
!
purchase and legalization of land;
!
architectural and engineering planning and works;
!
purchase of machines and tools;
!
capital expenditure (interest and amortization) and depreciation.
Expenditure
!
personnel (non-qualified labour; technical, management and administration teams);
!
operation and maintenance;
!
energy and tariffs of public service concessionaires;
!
spare parts and machine replacement.
Income
!
direct
!
!
sale of compost and recyclable material.
indirect
!
!
savings through the reduced cost of transport to the sanitary landfill;
savings through reduced sanitary landfill costs resulting from reduced
waste volumes.
175
Environmental
!
energy savings;
!
natural resource savings;
!
reduced environmental contamination from waste.
Social
!
provision of dignified and formal employment for segregators – the participation of
segregator organizations in plants should be prioritized whenever possible;
!
income generation;
!
promotion of public environmental awareness.
It is unlikely that the direct income from a segregation and composting plant will cover
its expenditures and the project should not be entered into as a profitable undertaking
from a strictly commercial perspective. However, taken as a whole, it can be seen as
being extremely positive when indirect income and the potential for significant
environmental and social benefits are considered.
Segregation and composting plants generate income and employment
and reduce the amount of waste to be disposed of in sanitary landfills
or refuse dumps.
The use of recyclable material results in a saving of energy and
resources that would otherwise be used in the transformation of raw
materials and this, together with the transformation of organic matter
separated from waste into compost that improves agricultural soils,
represents a significant environmental and economic benefit from
segregation and composting plants.
RECYCLABLE
MATERIALS MARKET
The market for recyclable material is growing rapidly and offers significant rates of
return, although there has been a concomitant increase in quality requirements.
Companies that buy recyclables impose three basic conditions:
176
!
sufficient production scale;
!
regularity of supply;
!
good quality material.
12. Solid waste treatment
Materials that are appropriately segregated, relatively clean, and so more valuable, are
easier to commercialize in the market.
The commercialization of these products, including the sale price and production flow,
depends on the existence of local recycling companies that are interested in them.
Market prices vary and are directly influenced by the price of raw materials as well as
other factors such as the level of demand from recycling companies for a particular
recyclable material at certain periods of the year.
Some segregator cooperatives seek ways of increasing the value of their recyclable
material by for example endeavouring to make it as clean as possible and at least
segregating and baling the different types of paper and cardboard, aluminium cans and
hard plastic. They will also endeavour to sell directly to companies, eliminating intermediary
agents. Another fundamental requirement is to have a storage place for the materials
in order to rationalize their transport to the customer and be able to offer larger
amounts of recyclable material and in consequence obtain better prices.
12.3
Treatment of special domestic waste
12.3.1 Construction rubble
The most common treatment of construction rubble is its segregation, cleaning and
grinding for reuse in the construction industry itself.
Recycled rubble can be used in the base and sub-base of roads or as gross aggregate
in construction works, reinforced concrete works of art and pre-moulded elements.
The recycling of construction rubble has the following advantages:
!
a reduction in the extraction of raw material;
!
the conservation of non-renewable raw material;
!
an improvement in the urban environment due to reduced indiscriminate dumping
of construction rubble in the streets;
!
the availability on the market of cheaper construction materials;
!
the creation of employment for unqualified labour.
The establishment of recycling plants for this type of material should therefore be
fostered and the possibility of charging special tariffs should be considered to ensure
their economic viability.
Three factors should be analyzed in a pre-establishment evaluation for a rubble recycling
plant in a particular location. In order of importance they are:
Demographic density – a high demographic density in the area is essential to ensure
a constant supply of rubble to the recycling plant.
Availability of natural aggregate – a scarcity of, or difficult access to, natural
deposits of raw material favours rubble recycling. However an abundance of, and
177
easy access to, natural deposits does not necessarily exclude the viability of rubble
recycling.
Technical level – it is necessary to use appropriate technologies to avoid environmental
degredation.
The location of a recycling plant on the periphery of an urban area is of fundamental
importance in order to keep the final cost of the recycled product down. Also, the
following factors should be studied:
In connection with rubble received:
!
!
!
!
rubble characteristics (quantity, type and quality, place of origin, responsible
agent, regulations in force);
demolition and renovation (techniques applied, rubble transport);
collection and final disposal possibilities (prices, distances, existing local
regulations);
processing (feasibility, technical team, organization and machines).
In connection with commercialization:
!
natural raw material (quality, price, reserves);
!
market conditions (type, current consumption, standards);
!
recycled material (technical quality, quantity, price).
Figure 98 - Rubble recycling plant - basic features
178
1
2
3
4
5
6
7
8
9
10
11
-
Administration
Control centre
Entry checkpoint
Feeder
Grinder
Conveyor belt
Rubble to be recycled
Storage Area
Reception Area
Green Belt
Garden
12. Solid waste treatment
Construction rubble recycling can be done in two ways: automatic and semi-automatic.
The automatic process employs a robust machine of great potency, able to receive
and grind construction rubble without the prior separation of iron rods that therefore
remain inside concrete blocks. After being ground the material passes through a
magnetic separator to remove ferrous material, which is pressed, baled and
commercialized. The rest of the material passes through a revolving sieve that
segregates it according to granulometric characteristics.
In the semi-automatic process iron is separated before grinding.
Figure 99 - General view of a rubble recycling plant
The plant should receive only inert waste so that there is no possibility of releasing
contaminating substances. The appropriate procedures and control devices should be
adopted to avoid the emission of particles.
The grinder feeder should be equipped with water sprinklers to minimize the emission
of dust and a rubber lining to keep noise levels within the limits established by
environmental control bodies.
Operational sequence for a semi-automatic plant
!
rubble brought in by collection trucks is weighed on the recycling plant’s weighbridge
and sent to the reception area;
!
in the reception area it is superficially inspected to determine whether the load is
compatible with the grinder. If it is not of an appropriate type, the unloading of the
vehicle will not be allowed and it will be sent to a sanitary landfill;
179
!
if the material is compatible with the machinery the vehicle unloads in the reception
area. Manual segregation takes place there, separating out material of no use such
as plastic, metal and small amounts of organic matter;
!
during manual segregation a mechanical loader is used to stir the material and facilitate
the work of segregators;
!
the separated out material is categorized into what can be commercialized (scrap
iron) and what is for disposal (the rest of the material), and is put in separate areas
for storage and future disposal respectively;
!
material with larger dimensions than those of the feeding mouth is not accepted,
nor concrete blocks with internal iron rods that can damage the mill by breaking the
hammers. In some cases reception area workers can break the blocks and separate
out the iron;
!
material in which significant amounts of plastic are incorporated must never be
admitted as it can damage the machines;
!
rubble from small construction works often arrives in bags and is manually unpacked
before the feeding and grinding operations;
!
once material that is of no use has been removed, the rubble is lightly dampened by
a sprinkler system in order to minimize the dust generated during grinding. A mechanical
loader then places it in the feeder, which regulates its entry into the grinder.
Figure 100 - Rubble recycling plant - feeder and grinder
!
from the feeder the material passes to the mill where it is ground. From the grinder
the material moves along a small conveyor belt equipped with a magnetic separator
to separate iron that was not seen during the manual segregation and was introduced
into the impact mill;
180
12. Solid waste treatment
!
later the material passes to the vibratory sieve that segregates it according to
predefined granulometry;
!
each type of material is transported to its respective storage area on a conventional
constant speed conveyor belt.
Conveyor belts are mounted on wheels so that they can be moved sideways in a semicircle in the storage area. This facilitates direct transportation to the storage area in an
interrupted operation that avoids the need to move piles of ground material with a
mechanical loader.
Figure 101 - Rubble recycling plant - grinder and conveyor belt
The conveyor belt wheels should move on a concrete surface strong enough to support
its weight. The sideways movement of the belt is a manual operation carried out by
storage area workers each time that the pile of ground rubble reaches the maximum
height allowed by the incline of the belt.
In the storage area the ground material should always be kept damp to avoid scattering
by the wind and dust generation.
Vehicles that take ground rubble away are loaded with a mechanical loader similar to
the one used in the reception area.
Products made with recycled rubble include:
!
pavement paving slabs;
!
road sub-base and base;
!
breeze blocks for cheaper housing walls and masonry;
!
fine aggregate for surfacing;
!
aggregate for storm drain inlet, kerb and gutter construction.
181
The costs presented here are based on the establishment and operation of a large
automatic rubble recycling plant with a 100 ton/hour production capacity located 10km
from the urban perimeter:
!
cost of the plant (construction work + machines): US$ 1,091,274.33
!
unit production cost: US$ 10.30/ton
The establishment and operational costs for a semiautomatic plant are as follows:
A 120 ton/day capacity plant:
!
investment costs: US$ 45,000.00
!
construction work: US$ 25,000.00
!
maintenance/operation: US$ 11.50/ton
A 240 ton/day capacity plant:
!
investment costs: US$ 80,000.00
!
construction work: US$ 30,000.00
!
maintenance/operation: US$ 13.60/ton
12.3.2 Tyres
Problems caused by the inappropriate disposal of tyres in wasteland, watercourses
and streets, especially in peripheral urban areas, are a source of growing concern for
public authorities due to their significant environmental impacts.
Due to climatic conditions and other characteristics particular to Latin American and
Caribbean countries, the problem is of equal concern from a public health perspective
as inappropriately discarded tyres become a shelter and breeding ground for disease
vectors due to the water that accumulates in them.
In the United States, where the consumption of tyres is equivalent to one tyre per
inhabitant per year (approximately 300 million tyres a year), the most common treatment
is burning in thermoelectric plants. However due to difficulties involved in this process
it is applied to no more than 5% of used tyres.
In both the 100 million dollar Modesto plant in California, which burns 4.5 million tyres
a year generating 15 megawatts and providing energy to 14,000 houses, and the Sterling
plant in Connecticut, which burns 10 million tyres a year generating 30 megawatts,
operational costs are double those for coal burning plants.
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12. Solid waste treatment
The disposal of used tyres in sanitary landfills is inappropriate as there are operational
problems involved in burying them and they provoke empty spaces that cause points
of instability in the mass of waste. Consequently alternatives have been sought to
address this problem but up to now no definitive solution has been found.
This problem came to the fore in Brazil in the mid 1990s when the annual tyre
production had reached 35 million. At the end of that decade CONAMA introduced a
requirement obliging tyre companies to take responsibility for the disposal of waste
resulting from their production (used tyres) under the “polluter pays” principle. Burning
in cement industry clinker furnaces was the immediate solution that producers turned
to. However not all furnaces were adapted to burn tyres and there were some restrictive
factors associated with the procedure because of a change in the quality of the cement
produced and the emission of gases not in compliance with limits established by
environmental bodies.
In recent years the ongoing search for new technological processes has seen
developments such as one in Brazil that uses organic solvents to separate rubber
from the wire and nylon in tyres facilitating its recovery and recycling. However, many
of these new developments are not economically viable.
In spite of these efforts the problem continues and, as in other situations, it is the
urban cleaning system that has to bear the significant expenditure involved in dealing
with used tyres habitually discarded in unpopulated peripheral areas as it has an
obligation to collect them for sanitary and environmental reasons.
In this context, an initiative that can serve as an example for other urban cleaning
bodies in Latin American and Caribbean cities is the COMLURB “ecotyres” experience
in Rio de Janeiro.
Concerned with the growing number of used tyres discarded in the city, a study was
carried out on the route taken by tyres from their moment of purchase in different
neighbourhoods of the city to the moment when they are discarded, in general in
peripheral zones.
The study found this route to be: producers, dealers, recovery agents and tyre workshops. Tyres without any further possibility of use are discarded on wasteland, in
drainage channels or are burned.
This data led to the following measures: the registering of all locations, both formal
and informal, where tyres are repaired; the implementation of the “ecotyres” system 5
in cooperation with the private tyre sector; and the development of an information
program on the use of the “ecotyres” system covering dealers, tyre mechanics, bus
companies and haulage companies.
5.
A network of locations with the minimum infrastructure necessary for the reception and storage of unusable tyres that, when a
predetermined number have accumulated, are then taken away by the private sector to be recycled.
183
The public authority should introduce specific regulations that consolidate the
application of the “polluter pays” principle by establishing the responsibilities of
producers and distributors for waste generated when their products are discarded.
12.3.3 Batteries and fluorescent tubes
The number of batteries present in domestic waste continues to increase as the use
of electrical and electronic gadgets spreads in modern society and plays an increasing
role in people’s daily lives.
The incidence of this type of waste in the overall composition of domestic solid waste
is clearly dependent on the socioeconomic condition of the population as here the
relation between consumption and disposal is direct. In Latin American and Caribbean
countries the problem has therefore yet to reach the concerning proportions that it
has in the United States, Japan and European countries.
However immediate action is necessary to establish control mechanisms for this
type of waste as it should receive the same level of treatment as hazardous industrial
waste.
Fluorescent tubes fall into a similar category and due to their high level of toxicity,
together with the difficulties involved in controlling environmental contamination
from them, they should be dealt with in the same way as toxic waste.
In the cases of both batteries and fluorescent tubes specific legislation is required
to consolidate the “polluter pays” principle. Under such legislation responsibility
for the treatment and final disposal of these types of waste would be assigned to
producers, with the participation of dealers and distributors in the reception of
discarded material and of the general public in separation, appropriate storage and
delivery.
12.4
Treatment of waste from special sources
12.4.1 Industrial solid waste
It is usual to treat industrial waste with a view to its reuse, or at least to leaving it inert.
Due to its diversity however there is no pre-established universally applicable process
so research and development for economically viable processes is always needed.
This waste should not be the responsibility of the urban cleaning authorities but of
the waste generators themselves, the industrial companies that produce it. Such an
184
12. Solid waste treatment
approach requires comprehensive legislation and effective supervision mechanisms
to avoid irregular disposal of the waste.
Recycling and recovery
In general there is a trend towards transforming waste into base material for other
processes, thus generating savings in the industrial process. However transformation
processes require significant investment and offer unpredictable returns as the scope
for corresponding charges on the price of the product is limited, but this risk reduces
as technological developments provide more secure and economical ways of using
the material.
To encourage waste recycling and recovery, some states issue free periodical
publications in which industrial companies anounce waste that they have for sale or
donation, or waste that they want to purchase.
Other treatment processes
The most common treatment processes are:
!
neutralization – for waste with acid or alkaline characteristics;
!
drying by mixing – the mixing of waste that has a high humidity content with dry
waste or inert material such as sawdust;
!
encapsulating – the lining of waste with a coat of impermeable synthetic resin with
a very low leaching level;
!
incorporation – the adding of waste to a mass of concrete or clay in a proportion
that does not damage the environment, or the adding of it to combustible material
where gases that are harmful to the environment will not be generated during
burning;
!
thermal destruction – incineration and pyrolysis.
12.4.2 Radioactive waste
There are still no economically viable treatment processes for radioactive waste. Atomic
stabilization processes for radioactive material have been developed but still cannot
be used on an industrial level.
As has already been explained this type of waste is the responsibility of a specialized
national body that operates within international regulations and safety procedures,
without any participation by the urban cleaning sector.
185
12.4.3 Port and airport waste
This type of waste is not usually treated in a special way except in the case of
waste generated on boats or planes coming from regions where a particular disease
is endemic. In such cases it is important that the work of the urban cleaning team
is integrated with that of the professionals responsible for sanitary vigilance so
that appropriate sanitary and environmental procedures can be applied to the
storage, collection, treatment and final disposal of this waste. Incineration, or
another equivalent treatment, is usually recommended for waste with a high
potential risk.
In general most waste generated on these sites has similar characteristics to domestic
waste and can be collected and sent to the same final disposal units.
12.4.4 Medical waste
There are many technical processes for the treatment of medical waste. Until a short
time ago the debate on medical waste treatments was between incineration and
autoclave treatment as many countries do not allow its disposal in septic tanks at
sanitary landfills.
Recent progress in environmental research led to the discovery of atmospheric
contamination risks in the incineration process and resulted in a requirement for very
expensive treatments of generated gases, which has imposed economic restrictions
on its use.
New technical processes have led to the development of several treatments that are
already available on the market. Irrespective of its technical basis any waste treatment
that is adopted should:
!
reduce the biological content of waste in accordance with stipulated requirements,
that is, the elimination of bacillus stearothermophilus in the case of sterilization
and of bacillus subtyllis in the case of disinfection;
!
comply with regulations established by the government’s environmental control body
for effluents and gas emissions;
!
avoid the de-characterization of waste thus ensuring that it is recognizable as medical
waste;
!
process sufficient volumes in relation to the capital and operational costs of the
system in order to be economically viable in terms of the local economy.
The available commercial processes that meet these fundamental requirements are:
incineration, pyrolysis, autoclave, microwave, ionizing radiation, electro-thermal
deactivation and chemical treatment.
186
12. Solid waste treatment
INCINERATION
Incineration is a burning process in the presence of a high level of oxygen, through
which carbon based materials are decomposed, releasing heat and generating ashes as
residue. Normally the amount of oxygen used in incineration is 10% to 25% greater
than is necessary in the common burning of waste.
Correctly carried out waste incineration is also an effective means of reducing the
volume of waste and leaving it absolutely inert in a short time. However installation and
operational costs are generally high principally because of the need for filters and
sophisticated technological devices to reduce or eliminate the contamination of the
air with gases produced during the burning of waste.
Basically an incinerator consists of two combustion chambers. In the first chamber
solid and liquid waste is burned with a high level of oxygen at a temperature of
800ºC to 1,000ºC, transforming it into gases, ashes and scoria. In the second chamber
gases produced by the initial combustion are burned at a temperature of 1,200ºC
to 1,400°C.
Gases resulting from the secondary combustion are rapidly cooled to avoid the recomposition of their extensive toxic organic chains and are then treated in washers,
cyclones or electrostatic precipitators, before being discharged into the atmosphere
through a chimney.
As the waste burning temperature is not high enough to melt and volatilize metals,
they become mixed with the ashes from where it is possible to separate and recover
them for commercialization.
In the case of toxic waste that contains chlorine, phosphorus or sulphur, gases not
only need to remain for more time inside the chamber (approximately two seconds)
but also require treatment by sophisticated systems before they can be discharged
into the atmosphere.
In the case of waste composed exclusively of carbon, hydrogen and oxygen atoms all
that is required is an efficient system to filter particles expelled together with the
combustion gases.
There are different types of incineration furnace, the most common being fixed grate,
moving grate and rotary kiln.
187
Fixed grate incinerators
In this process waste is deposited on a fixed grate where it is burned. Air is introduced
from above the grate to minimize the trailing of ashes. Ashes and scoria resulting from
the burning process fall through the holes of the grate into an ash pit, from where
they are removed mechanically or by water.
To ensure the level of oxygen necessary for the complete combustion of waste
and gases, the air flow is augmented by an extractor located at the base of the
chimney.
Chimney
Overhead crane
Feeding
Collection
truck
Air
blower
Fixed grate
Reception
pit
Contamination
control
equipment
Combustion
chamber
Ash outlet
Air
extractors
Ash outlet
Figure 102 - Fixed grate incinerator
Moving grate incinerators
The grate consists of stepped cast iron sheets connected to a hydraulic system for
moving it in a swaying motion that conducts the waste from the access door through
to the ash and scoria pit.
The combustion grate is divided into three sections, the first one is for drying and the
waste is completely burned in the second and third sections.
Air for combustion in the furnace is provided by two blowers, one that blows air
amongst the waste (air below fire) and the other that introduces air above the waste
(air above fire).
Hot ashes and scoria from the burning are continuously deposited in a pit located
under the furnace from where they are removed mechanically or by water.
188
12. Solid waste treatment
Chimney
Ventilation
blower
Swaying
grate
Steam
control valve
Overhead crane
to transport waste
Use of heat generated
by waste
Steam turbine
Condensation
tank
Overhead crane
to transport ashes
Heater
Condenser
Gas cooler
Filter
sleeve
Gas
re-heater
Overhead
crane for
bulky waste
Reagent
catalytic
reactor
Fly ash
treatment
Furnace
Bulky
waste pit
Bulky
non-combustible
waste
Magnetic separator
Aluminium
separator
Ferrous
material press
Hammer
grinder
Ferrous
material storage
Rotary
sieve
Ventilation
blower
Ash pit
Conveyor belt
for ashes
Waste pit
Gas
washer
Bulky combustible waste
Ground
combustible
material
Slow speed
blade grinder
Aluminium
press
Aluminium
storage
Figure 103 - Moving grate incinerator
Rotary kiln
Rotary kilns are useful for the thermal destruction of infectious waste but are more
used for burning hazardous industrial waste. They are cylindrical incinerators with a
diameter of approximately four metres and a length of up to four times the diameter,
mounted with a slight incline in relation to the horizontal plane.
The entrance is at the higher end, the opposite end to the burners, so that the waste
moves slowly downwards due to the rotation of the cylinder.
Gases generated pass to a secondary burning chamber that accommodates burners
for liquids and gases. Gases resulting from this burning flow into heat interchangers
and washing equipment.
Chimney
Heat
interchanger
Feeder
system
Gas
washer
Liquid
waste burner
Rotary
kiln
Washer water
oxidation
Electrostatic
filters
Air
extractor
Collection
truck
Reception
pit
Post-burning
chamber
with chimney
Figure 104 - Rotary kiln
189
PYROLYSIS
Like incineration, pyrolysis is a thermal destruction process with the difference that it
absorbs heat and takes place in the absence of oxygen. In this process, carbon based
materials de-compose into combustible gases or liquids and carbon.
Pyrolytic furnaces are very much used in the treatment of medical waste, where the
calorific value of the waste maintains a certain temperature during the process.
There are single chamber models where the operating temperature is approximately
1,000ºC and dual chamber models with temperatures of between 600ºC and 800ºC in
the primary chamber and between 1,000ºC and 1,200ºC in the secondary chamber.
Primary air
Temperature
Gradient
Drying
Secondary air
Decomposition
Gasification
,
Cyclone
Boiler
Air extractor
Ash extractor
Figure 105 - Pyrolytic furnace
The feeder system can be automatic (continuous) or semi-automatic (by lots) and the
auxiliary burners can burn diesel or gas.
Its main advantages are:
!
effective treatment is guaranteed given optimum operational conditions;
!
substantial reduction in the volume of waste to be disposed of (almost 95%).
Its main disadvantages are:
!
190
high operational and maintenance costs;
12. Solid waste treatment
!
maintenance difficulties requiring constant cleaning work in the auxiliary fuel feeder
system, unless natural gas is used;
!
high risk of air contamination from dioxins generated by the inappropriate burning
of chloro materials present in PVC bags and disinfectants;
!
risk of air contamination due to the emission of particulate matter;
!
high cost of effluent treatment.
It should be noted that neither incineration nor pyrolysis completely solve the medical
waste final disposal problem as both the ashes that are produced and the sludge
resulting from the treatment of gases require an appropriate final disposal.
Figure 106 - Medical waste incineration plant with a capacity of 250kg/hour
AUTOCLAVE
Originally used for the sterilization of surgical equipment, this process was adapted
and developed for waste sterilization.
Basically it consists of a feeder system that conveys the waste into a hermetic chamber
where a vacuum is created and steam is then injected (from 105ºC to 150ºC) under
certain pressure conditions.
191
The waste remains in the chamber for a certain period until it is sterile, after which
water is discharged from one side and the waste from the other.
Figure 107 - Autoclave
Advantages:
!
relatively low operational costs;
!
does not emit gases and effluent is sterile;
!
relatively easy and cheap maintenance.
Disadvantages:
!
there is no guarantee that the steam will reach all parts of the mass of waste unless
it has been appropriately ground before the sterilization phase;
!
does not reduce the volume of waste unless it is previously ground;
!
waste is processed in lots, continuous treatment is not possible.
MICROWAVE
In this process waste is ground, dampened with steam at 150ºC and is fed, as a
continuous process, into a microwave furnace where there is a device to stir and
transport the mass so that all of the material uniformly receives the microwave radiation.
192
12. Solid waste treatment
Advantages:
!
absence of emissions or any type of effluent;
!
continuous process.
Disadvantages:
!
relatively high operational costs;
!
the volume of waste to be buried is not reduced unless it is ground.
Figure 108 - Microwave
IONIZING RADIATION
In this process, waste in its natural form is exposed to the action of gamma rays,
generated by a source of enriched cobalt 60, which render micro organisms inactive.
This process has the following disadvantages in comparison with previously mentioned
processes:
!
treatment effectiveness is questionable as a possibility exists that part of the mass
of waste is not exposed to the electromagnetic rays;
!
the used cobalt 60 source (radioactive) requires appropriate disposal.
Its advantages are the absence of any type of effluent emission and the fact that it is
a continuous process.
193
Deodorizer
Deodorizer
HEPA Filter Pre-filter
Dust
collector
HEPA Filter Pre-filter
Hydraulic
press
Automatic
doors
Weighbridge
Reception
pit
Primary grinder primary cyclones
Secondary grinder secondary cyclones
Liquids
Grinding and homogenization
Waste reception
Processing
unit
To the
landfill
Container
Press
Control
panel
Transport
Class C
waste
Treatment
Figure 109 - Ionizing radiation
ELECTRO-THERMAL
DEACTIVATION
This process consists of double grinding prior to treatment, followed by the exposure
of the ground mass to a high potency electrical field, generated by low frequency
electromagnetic waves, reaching a final temperature of 95ºC to 98ºC.
In this process there is no effluent or gas emission.
The advantages and disadvantages of this process are the same as those for the
microwave process, with the addition of equipment maintenance difficulties, and there
is no volume reduction unless a post-treatment grinding system is installed.
CHEMICAL TREATMENT
In this process waste is ground and then submerged in a disinfectant solution that
can be sodium hypochlorite, chlorine dioxide or formaldehyde gas. The mass of
waste remains in the solution for some minutes and the treatment is by direct
contact.
194
12. Solid waste treatment
Before being deposited in the outlet container, waste passes through a drying system
generating an environmentally harmful effluent that has to be neutralized.
The advantages of this process are its low operational and maintenance costs and the
effectiveness of the waste treatment.
The disadvantages are the need for effluent neutralization and the absence of volume
reduction unless the waste is ground, which would have to be a separate process.
Particle
filtering
Bags of
medical
waste
Air extractor
HEPA filter
Rotary discharge
screw conveyor
Grinder Nº 1
sc
re
w
In
cli
ne
d
½ to 2
inch grater
Pulverizer Nº 1
(disinfectant)
co
nv
ey
or
Mixer
Grinder Nº 2
½ to 2 inch
grater (dry)
Vertical screw conveyor
Pulverizer Nº 2
(disinfectant)
Feeder
Vapour
Gas washing
Discharge tube
Sodium
hypochlorite
solution
Im
m
er
sio
n
Horizontal screw conveyor
Figure 110 - Chemical disinfection
195
13
196
Solid waste final disposal
13. Solid waste final disposal
13.1
Introduction
Urban cleaning systems have to face the challenge not only of collecting solid waste
from streets and buildings in ever-growing cities but also of ensuring an appropriate
final destination for such waste.
The latter issue deserves attention because if collection is inefficient public pressure
is put on the municipality to improve service quality due to it being an exposed and
visible activity, while if the final disposal of waste is carried out in an inappropriate
way, few people will be directly disturbed by this and so it will not generate complaints.
Consequently, as many municipalities in Latin America and the Caribbean have a limited
budget, the urban cleaning system will tend to leave final disposal in the background
giving priority to waste collection and street cleaning.
As a result in many municipalities, particularly the smaller ones, it is common to find
refuse dumps where collected waste is deposited directly on the ground without any
supervision or environmental care, contaminating soil, air, the water table and
neighbouring land.
In addition to the sanitary and environmental problems that refuse dumps present,
there are serious social problems connected with the segregators that they attract.
These people make their living from the separation of recyclable material and often
live in huts and shacks on the site of the dump, raising families and even forming
communities.
The only appropriate form of solid waste final disposal is in sanitary landfills or, provided
certain conditions that will be described later are fulfilled, in controlled landfills. All the
other processes that are regarded as disposal (recycling, composting and incineration
plants) are in reality waste treatment processes that need a landfill for the final disposal
of the remaining waste.
The initiation of a sanitary landfill presents difficulties not only because it involves
environmental studies, specific sanitary engineering and environmental planning and a
relatively high initial investment before it is established, but also due to the natural
resistance that arises in people when they know that they will be living close to a place
where waste will accumulate.
This rejection stems from a perception that society has of solid waste disposal sites
as being inadequately set up and badly managed. It is therefore necessary to defeat
this stigma through thorough studies and project planning, and with a broad awareness
raising process in society that communicates the difference between sanitary landfills
and dumps. At the same time, it is essential that the political will exists to allocate the
necessary budgetary resources for the implementation and correct operation of the
approved project.
197
13.2
Impacts of inappropriate solid waste disposal
Problematic situations often encountered around the site of incorrect municipal solid
waste disposal and their respective consequences are:
!
proximity to bodies of water ! water contamination;
!
lack of covering, or only partial covering, of waste ! vector proliferation, odours,
unsightliness and landscape contamination;
!
practice of burning waste ! safety risks for people, atmospheric contamination,
energy wastage;
!
lack of physical barriers (areas without fences) and a vegetation belt ! access for
people and animals, dispersion of odours and waste particles;
!
inappropriate disposal of medical waste mixed with domestic waste ! increased
risk to people and of environmental contamination;
!
pig raising and presence of other animals ! zoonosis and other public health risks;
!
proximity to population centres, educational centres and kindergartens !
inhabitants subject to various nuisances and sanitary risks;
!
segregation activities carried out by women, men, old people and children !
citizenship degradation, exposure to unhealthy conditions, health risks and accidents;
!
proximity to environmentally protected areas (ecological reserves and equivalents)
! degradation of the area and environmental contamination risks.
Landfills are a kind of melting pot for chemical and biological activity and reactions that
produce effluents, the nature of which depends on the components of the waste,
hence the previous segregation of special waste is indispensable.
At the final disposal site the biological decomposition of the remains of food and
other organic material contained in domestic waste generates an effluent with a high
BOD (biochemical oxygen demand) that moves and incorporates other substances
contained in the mass of waste. As a result this leachate is highly contaminating due to
its high BOD and chemical reactions between its components (heavy metals, for example).
In addition domestic solid waste anaerobic decomposition processes generate biogas,
principally composed of methane, which is explosive in concentrations of 5% to 15% in
the air. Biogas is not only toxic but is one of the contributory factors to the greenhouse
effect. The composition of this biogas includes gases with an unpleasant smell such as
hydrogen sulfide and mercaptans.
Measures to avoid the negative effects that result when waste is inappropriately disposed
of on the ground should include the creation of an environment less favourable for
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13. Solid waste final disposal
undesirable chemical and biological reactions. It is therefore necessary to isolate or
minimize the contact between waste components that could react with each other.
Finally it is necessary that effluents and gases are dealt with in an appropriate way.
A solid waste final disposal project should therefore incorporate technical solutions
that comply with the basic guidelines for avoiding the above mentioned environmental
impacts.
In a solid waste final disposal unit the soil is the principal receptor and conductor of
contaminants. Nevertheless it can also serve as protection against the contamination
of underground water and the environment provided that it is sufficiently deep and
impermeable. Where these favourable conditions do not exist naturally, engineering
resources should be used to comply with the required technical specifications and
applicable regulations.
The recommended method for domestic waste final disposal is the sanitary landfill. In
Latin American and Caribbean countries an acceptable alternative for smaller
municipalities with limited economic resources is the controlled landfill, which can be
used provided that technical and environmental norms established by regulatory legal
instruments are respected.
13.3
Sanitary landfill
The objectives and principles of sanitary landfill construction and operation can be
defined in different ways. In our opinion the most appropriate definition is the one
established by the Sanitary Engineering and Environmental Sciences Pan-American Centre
(CEPIS, in Spanish), of the Pan American Health Organization, which has been
incorporated in many technical norms and adopted by environmental bodies and entities.
It states that:
“The sanitary landfill is a technique for the final disposal of solid waste in the ground
that causes no nuisance or danger to public health or safety; neither does it harm the
environment during its operations or after its closure. This technique uses engineering
principles to confine the waste to as small areas as possible, covering it daily with
layers of earth and compacting it to reduce its volume. In addition, it anticipates the
problems that could be caused by the liquids and gases produced by the decomposition
of organic matter.”
A sanitary landfill unit of construction is called a cell, in which each day’s solid waste
(or the waste from a shorter period if the daily amount of waste is too great) is deposited
in compacted sloping layers and is covered with a layer of earth that is also compacted.
The cell is built against a retaining wall that can be a pre-existent natural elevation, a
berm previously formed with compacted earth or other cells. Cells are constructed
next to each other, each one supported by the previous one, forming a “landfill level”;
the landfill can have two or more levels, depending on project requirements.
199
When determining the dimensions of a cell, some basic criteria should be taken into account:
!
the width of a cell’s work face should not be greater than is necessary for the safe
manoeuvring of machines and vehicles;
!
the height should be between 3 and 6 metres depending on the amount of waste
to be dealt with (sanitary landfill capacity);
!
the advance should be calculated according to the daily volume of waste, the width
of the work face and its height;
!
dimensions are adjusted according to the stability and availability of the land.
A sanitary landfill consists of operational and support units.
Operational units
!
domestic waste cells;
!
medical waste cells (where the municipality does not have a more effective final
disposal process for this type of waste);
Figure 111 – Construction of the operational area - Embankment
!
waterproofing of the bottom (obligatory) and of the top (optional);
Figure 112 – Waterproofing of the operational area
200
13. Solid waste final disposal
!
collection and treatment system for percolated liquid (leachate);
Figure 113 – Leachate collection and treatment
!
biogas collection and burning (or use) system;
Figure 114 – Biogas collection and burning
!
rainwater drainage and channelling system;
Figure 115 – Rainwater drainage system
201
!
environmental, topographical and geotechnical monitoring systems;
!
storage area for materials.
Figure 116 – Storage area for materials
Support units
!
fence and vegetation barrier;
Figure 117 – Vegetation barrier
!
access and service roads;
Figure 118 – Preparation of an internal service road
202
13. Solid waste final disposal
!
weighbridge for trucks and waste checkpoint;
Figure 119 – Weighbridge for weighing loads
!
entrance checkpoint and administrative offices;
!
mechanical and tyre workshops.
Figure 120 – Support units
The sanitary landfill pre-operational process consists of the selection of the site,
obtaining the necessary licenses, formulating the project master plan and installation.
13.3.1 Sanitary landfill site selection
The selection of the sanitary landfill site is a complex task. The intense urbanization
and land use in cities limits the availability of sites that are both close to where waste
is generated and large enough for the installation of a sanitary landfill that will meet
the needs of the municipality.
Many other factors have to be taken into account such as the technical requirements
of the norms and guidelines issued by relevant public bodies, juridical aspects,
203
governmental requirements, the governing plan of the corresponding municipality, local
and regional development centres, the distance over which waste will have to be
transported, access roads and political and social aspects involved in the approval of
the project by politicians, the media and the community.
Economic and financial factors must be a major consideration as municipal resources
always have to be used in a balanced way.
Requirements for the appropriate establishment of a sanitary landfill are therefore
very rigorous and it is necessary to carefully define an order of priorities.
The selection strategy for a new sanitary landfill site consists of the following steps:
!
preliminary identification of land available in the municipality;
!
determination of all selection criteria;
!
definition of the selection criteria order of priority;
!
a critical analysis of each potential site in relation to the prioritized criteria, so that
the site that most complies with the required conditions in terms of its natural land
characteristics is selected.
Applying this strategy minimizes the corrective measures that have to be taken to
adapt the land to technical requirements and thus reduces the need for initial
investment.
PRELIMINARY IDENTIFICATION
OF AVAILABLE SITES
The preliminary identification of available sites in the municipality should be carried out
as follows:
!
preliminary calculation of the total area needed for the sanitary landfill;
To make an approximate calculation of the minimum total area necessary for the
installation of a sanitary landfill, in square metres, some experts multiply the quantity
of waste collected daily, in tons, by the factor 560. This factor is based on the following
landfill project parameters:
Useful life = 20 years; landfill height = 20 m; slopes of 1:3 (vertical : horizontal) and an
80% operational occupation of the land.
However the operational usage as a percentage of the total area will depend on the
particular conditions of each site (topography, hydrology and geometric shape, for
example).
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13. Solid waste final disposal
!
perimeter delimitation of rural and industrial zones and conservation areas existing
in the municipality;
!
survey of the available sites within the delimited perimeters, where there are no
zoning or land use restrictions and sites have dimensions compatible with the
preliminary calculation, giving priority to land owned by the municipality;
!
determination of ownership of surveyed sites;
!
study of documents relating to the sites, excluding those where the documentation
is not in order.
It is very important that the legal situation in relation to the ownership of a site is in
order to avoid potential problems for the municipality and delays in the licensing process.
SELECTION CRITERIA
The criteria are divided into three groups: technical and legal, economic-financial, and
socio-political.
Technical and legal criteria
The selection of a sanitary landfill site for domestic solid waste final disposal should
fulfil the technical criteria imposed by technical norms and regulations stipulated by
the different levels of authority in each country.
All the conditions and restrictions commonly stipulated by technical norms and relevant
regulations are listed in table 17. It should be noted however that specific aspects of
legislation in any particular country may vary from the concepts and dimensions
described here, which in such cases should be appropriately modified.
Table 17
Technical and legal criteria
Criteria
Observations
The site should be outside the limits of any environmental
Land use
conservation areas and in a zone where designated land
use is compatible with the operation of a sanitary landfill.
Distance to
bodies of water
The site should be not less than 200 metres from major
bodies of water such as rivers, lakes, lagoons and oceans
and should be not less than 50 metres from any other
body of water.
205
Table 17 (cont.)
Criteria
Observations
Distance to urban
The site should be not less than 300 metres from urban
residential centres
residential centres with 200 or more inhabitants.
Distance to
airports
The site should not be located in the proximity of airports
or aerodromes and should comply with current legislation
in this respect.
The minimum distances recommended are the following:
!
in a sanitary landfill with plastic membrane waterproofed bottom, the distance between the water table
and the membrane should not be less than 1.5 metres;
Water table depth
!
in a smaller landfill the bottom of which is waterproofed
by a layer of compacted clay with a permeability coefficient of less than 10-6cm/s, the distance between the
water table and the waterproofing layer should not be
less than 3 metres.
Minimum
It is recommended that the site is compatible with a useful
useful life
life for the new sanitary landfill of at least 8 years.
It is recommendable that the soil of the selected site has
Natural soil
impermeability
good natural impermeability in order to reduce the
possibility of aquifer contamination. The soil of the
selected site should be clayey.
Topography
favourable to
The rainwater drainage basin should be small in order
drainage
landfill.
to avoid significant amounts of rainwater entering the
Roads leading to the site should not have pronounced
Easy access for
inclines or curves and should be well surfaced in order to
heavy vehicles
minimize wear and tear on collection vehicles and enable
them to have easy access even at times of intense rain.
Availability of
It is preferable that the site has, or is close to, deposits
material for
covering
of material appropriate for covering, in order to keep the
cost of waste covering low.
The length of a sanitary landfill’s useful life is very important as it is increasingly difficult
to find new sites close to the collection area that are suitable for receiving the volume
of urban waste generated in the municipality. This is largely due to the natural rejection
of residents to having this type of waste final disposal unit close to where they live.
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13. Solid waste final disposal
Economic and financial criteria
Table 18
Economic and financial criteria
Criteria
Observations
The distance that collection vehicles have to cover on existing
Proximity to
roads and streets between the collection area and the sanitary
collection area
landfill should be as short as possible in order to minimize
wear and tear on trucks and waste transport costs.
If the land is not owned by the municipality, and therefore
Land purchase
costs
has to be purchased, it is preferable that it is located in a
rural area where purchase prices are lower than in other
areas where the landfill could be sited (industrial areas for
example).
Construction and
infrastructure
investment costs
It is important that the selected site has access to service
infrastructures in order to limit expenditure on water
provision, collection and treatment of local effluents, rain
water drainage, electricity supply, and communications
facilities.
Drainage system
maintenance costs
The selected site should have a gentle incline to avoid soil
erosion and limit expenditure on cleaning and maintaining
drainage system components.
Political and social criteria
Table 19
Political and social criteria
Criteria
Observations
The passage of vehicles transporting waste along residential
Access to the site
through low
streets constitutes an inconvenience for the inhabitants of
demographic
density areas
routes to the sanitary landfill pass through areas of low
those streets and it is therefore recommended that truck
demographic density and preferably on roads designed to
handle heavy vehicles.
It is recommended that a site is not chosen if there have
been previous problems between the municipality and the
Local community
acceptance
local community, non-governmental organizations (NGOs)
or the media in the area as any past disharmony with the
public authorities is likely to cause negative reactions to
the proposed landfill.
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SELECTION CRITERIA
ORDER OF PRIORITY
Table 20 shows a suggestion for the selection criteria order of priority in choosing a
sanitary landfill site.
Table 20
Criteria hierarchy
Criteria
Priority
Compatibility with environmental legislation
1
Compatibility with political and social conditions
2
Compatibility with the main economic conditions
3
Compatibility with the main technical conditions
4
Compatibility with other economic conditions
5
Compatibility with other technical conditions
6
In order to determine which is the best site for the sanitary landfill, each candidate site
should be the subject of an exhaustive analysis in regard to each of the established
criteria. For each criterion the analysis should allocate one of the following categories
and provide reasons for doing so: “total compatibility”, “partial compatibility, or total
with work” or “no compatibility”.
Both the priorities and the compatibility with the defined criteria are given a relative
weight, as shown in table 21.
Table 21
Weight given to criteria and compatibility
208
Priority of criteria
Weight
1
10
2
6
3
4
4
3
5
2
6
1
Compatibility
Weight
Total
100 %
Partial or total with work
50 %
No compatibility
0%
13. Solid waste final disposal
SELECTION OF THE BEST SITE
Analysis of candidate sites in relation to the established criteria
The site chosen for the sanitary landfill should be the one that is compatible with the
highest number of criteria, taking into account the relative priority of each one.
When the natural attributes of the selected site are not totally compatible with a certain
criterion, its deficiencies should be remedied by the application of modern engineering
solutions.
As an example we present the case of a municipality that has to determine which is the
best site amongst three pre-selected candidate sites, the characteristics of which are
shown in table 22.
The site with more points will be considered the best.
Table 22
Site characteristics
Criteria
Priority
Compatibility
Site 1
Site 2
Site 3
Distance from bodies of water
1
T
T
T
Distance from residential centres
1
T
T
P
Distance from airports
1
T
T
T
Water table depth
1
P
P
T
Access through low demographic
density areas
2
P
P
P
Acceptance by local community
2
N
P
T
Land purchase costs
3
P
P
T
Existence of infrastructure
3
T
T
P
Minimum useful life
4
P
T
T
Land use
4
T
T
T
Natural impermeability of soil
4
P
P
P
Favourable topography for drainage
4
P
P
T
Easy access for heavy vehicles
4
T
P
P
Coverage material availability
4
N
P
T
Drainage system maintenance
5
P
P
T
Proximity to collection centre
6
T
P
P
Note: T = Total compatibility; P = Partial compatibility; N = No compatibility.
209
After the weighting process is applied, in accordance with table 21, the candidate sites
have the following points:
Table 23
Points for each site
Criteria
Priority
weight
Compatibility
weight
Points for
each site
Site
1
Site
2
Site
3
Site
1
Site
2
Site
3
Distance from bodies of
water
10
100%
100%
100%
10.0
10.0
10.0
Distance from residential
centres
10
100%
100%
50%
10.0
10.0
5.0
Distance from airports
10
100%
100%
100%
10.0
10.0
10.0
Water table depth
10
50%
50%
100%
5.0
5.0
10.0
Access through low
demographic density areas
6
50%
50%
50%
3.0
3.0
3.0
Acceptance by local
community
6
0%
50%
100%
0.0
3.0
6.0
Land purchase costs
4
50%
50%
100%
2.0
2.0
4.0
Existence of infrastructure
4
100%
100%
50%
4.0
4.0
2.0
Minimum useful life
3
50%
100%
100%
1.5
3.0
3.0
Land use
3
100%
100%
100%
3.0
3.0
3.0
Natural impermeability of
soil
3
50%
50%
50%
1.5
1.5
1.5
Favourable topography for
drainage
3
50%
50%
100%
1.5
1.5
3.0
Easy access for heavy
vehicles
3
100%
50%
50%
3.0
1.5
1.5
Coverage material
availability
3
0%
50%
100%
0.0
1.5
3.0
Drainage system
maintenance
2
50%
50%
100%
1.0
1.0
2.0
Proximity to collection
centre
1
100%
50%
50%
1.0
0.5
0.5
56.5
60.5
67.5
Points total
As can be seen, site 3, in spite of being located relatively close to a residential centre,
is the one that overall has the most advantages.
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13. Solid waste final disposal
After choosing the sanitary landfill site the municipality should not immediately proceed
with the purchase or compulsory purchase of the land as the project first needs
approval from the relevant environmental body, through a licensing process that is
based on deeper environmental studies.
13.3.2 Environmental licenses
The procedures for obtaining the necessary licenses for a sanitary landfill site depend
on formal processes and relevant legislation in each country.
The basic actions to take and process stages are presented here:
STAGE I
Approval of the land for landfill use
The objective of this stage of the environmental license application process is to
evaluate the selected site to determine whether it is appropriate for use as a landfill, in
comparison with other alternative sites.
The process begins with the presentation of a formal request by the applicant (the
municipality or private company, for example) to the relevant environmental body. This
document should be accompanied by general information about the site and the
conceptual basis of the sanitary landfill project.
Once the request is received, the environmental control body prepares technical
instructions (or terms of reference) in which the relevant aspects to be evaluated in
an Environmental Impact Study (EIS) are defined. The preliminary plan for the sanitary
landfill should be ready before this study is carried out.
EIS is a technical study, undertaken by specialized companies, with
the objective of determining the positive and negative aspects of the
project in regard to the physical (climate, geology, hydrology,
pedology, etc.), biotic (flora and fauna) and anthropic (related to
human activities) environment. It also establishes measures that can
be taken to avoid or diminish identified negative impacts.
As these studies are highly specialized, with complex methodologies and technical
terminology, a second report has to be prepared that presents a summary of the principal
finding of the EIS in a language that is accessible for the general public. Thus society in
general can form an opinion on the subject and participate democratically in the licensing
process.
It is important to note that environmental studies should be carried out with the
cooperation of technical teams from both the municipality and the environmental
control body, so that the methodology, technical guidelines and conclusions are, as
far as is possible, compatible with the policies of these entities.
211
Once completed, the studies should be immediately sent to the environmental control
body, which will analyze them and issue a technical opinion.
After this opinion is presented the community can be called to participate in public
hearings on the approval process, where this is the policy of the environmental control
body. In the specific case of a new sanitary landfill it is always advisable to hold such
public consultations.
EIS presentation at a public hearing should be accompanied by all available audio-visual
aids as the participating public will mostly be lay people who will better be able to
understand proposed solutions if they can see visual images of them.
Once the environmental impact study is approved, together with the pertinent palliative
measures, and after the necessary environmental impact compensatory measures are
established, the environmental control body will grant the authorization document
that licenses the selected site for the installation of a sanitary landfill. It should be
noted however that this license does not authorize the immediate commencement of
works, as first several complementary procedures have to be carried out by the applicant.
STAGE II
Authorization to commence sanitary landfill installation works
In the initial stage of the licensing process, and on the basis of the environmental
impact study, the environmental control body determines the conditions and restrictions
that the applicant has to comply with in order to obtain an environmental license to
commence sanitary landfill installation works.
The detailed engineering plan (master plan) should therefore take into account those
requirements and incorporate the concepts contained in the environmental impact
control and minimization plans recommended in the environmental assessment.
The compilation of field data must be completed in this stage, including detailed
topographical surveys and new geotechnical probes and tests. Detailed plans that deal
with environmental issues should also be completed, as should plans for layouts,
rainwater drainage, the collection and treatment of leachate, the collection and burning
of biogas, access and service roads, support unit buildings and landscaping.
The master plan should also include a detailed operational plan covering the operation of
the sanitary landfill, geotechnical and topographical monitoring, environmental monitoring,
weighbridge operation (if there is one) and machine, vehicle and equipment maintenance.
Finally detailed plans for foundations, superstructures, water and sanitation, electricity
supply, telephones, etc. are required.
Once completed, these plans should be submitted to the environmental control body
that will ascertain whether the requirements and conditions established when granting
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13. Solid waste final disposal
the stage I license have been met. If they have, the environmental body will issue the
license that authorizes commencement of sanitary landfill installation works.
STAGE III
Authorization for commencement of sanitary landfill operation
Once the environmental license authorizing the commencement of works is obtained,
the master plan begins to be put into practice, that is, earth works, excavation, drainage,
access road construction, etc. is carried out.
In this phase the applicant has to take into account that works should be carried out in
a way that rigorously respects not only the engineering plan but also control plans and
programs resulting from the environmental impact study that conditioned the approval
of the project by the environmental control body.
Consequently, paying attention to the circulation of vehicles and machines during the
work, the regulation of the internal combustion engines and the dispersion of
suspended particles in the work area, amongst other aspects, should be part of the
daily routine of engineers, overseers and all professionals involved.
Fulfilling the relevant environmental requirements and installing systems and devices in
accordance with the project plans are essential for obtaining the environmental license
that will authorize the operation of the sanitary landfill. Therefore, in addition to covering
the work itself, planning should include an efficient and responsible environmental
management strategy.
13.3.3 Master plan
The sanitary landfill master plan should maximize the useful life of the available area,
fully utilizing the natural characteristics of the land, minimizing installation costs and
ensuring appropriate environmental monitoring and safeguards.
In general it takes from 90 to 120 days to formulate a sanitary landfill master plan,
which has to rigorously comply with technical norms and environmental legislation.
The master plan should include the following documents:
!
planialtimetric plan for the landfill in an appropriate scale, with contour lines
representing each metre, and showing the location of accesses, plateaus,
constructions and other significant features;
!
geotechnical research and test results;
!
water quality analysis results for surrounding bodies of water and the water table;
213
!
access and service roads plan, including layout, earth works, surfacing and drainage;
!
construction plans, including the calculations for foundations and structures,
architectural design, landscaping and structures related to water and electricity
provision, communications, security and others;
!
external network plans for water, sewerage, electricity and rainwater drainage
systems;
!
layout plan for terraces, embankments and the final configuration of the sanitary
landfill and plans for each annual filling stage with cross sections;
!
plans for the collection and treatment of leachate, including bottom and top
waterproofing layers (where applicable), bottom drainage network, pumping network
and treatment plant;
!
superficial drainage plans for the landfill, including the slope of the platforms both
for the landfill’s intermediate stages and for the final stage, drainage of the definitive
berms, water drain pipes and discharge structures;
!
delimitation plans of sanitary landfill plots;
!
biogas collection and burning system plans, showing cross-sections and details;
!
environmental monitoring plan, including water table monitoring wells;
!
landfill operational manual covering the routine activities of solid waste disposal,
including leachate treatment plant operations and rainwater drainage network
maintenance;
!
a record of the calculations made for landfill and construction stability studies,
construction structures, superficial and deep water drainage networks, electricity
and water installations, the biogas collection and burning network and quantification
of machine, vehicle and labour requirements for landfill operation and maintenance;
!
technical specifications of all equipment, services and materials involved in the work;
!
sanitary landfill closure plan, including post-closure environmental monitoring plan.
Once the master plan has been approved, it is essential that it is presented to the
community using simple and direct language and the best audiovisual aids, informing
citizens about the nature of a sanitary landfill, the contamination control measures
that will be taken, the benefits of appropriate solid waste disposal and the
compensatory measures applicable to residents of the area. Such an approach will
help to avoid problems during the installation and operation of the sanitary landfill.
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13. Solid waste final disposal
13.3.4 Landfill installation
When the master plan has been approved and authorization for installation has been
obtained, work on the landfill can begin with fencing, land clearing and constructing
the foundations for a weighbridge (where applicable).
Works should always comply with technical specifications and all the other conditions
set out in the master plan, as well as with the requirements of technical norms,
government bodies that establish employment and work safety policies,
environmental control bodies, environmental legislation and norms and directives
issued by public service concessionaires (water, electricity, telephone, fire control
and others).
In medium-sized and large landfills the sequence of construction is in general as
follows:
SITE FENCING
Site fencing is necessary to discourage the entrance of non-authorized people and
animals such as dogs, horses, cows or pigs. An approximately two metre high fence is
recommended made of concrete or wood posts and galvanized wire with small spaces
in the lower part so that small animals cannot enter.
A barrier of vegetation should be planted along the wire fence with
a minimum width of 15 metres. The objectives of this are to block
the line of sight to the operational area, contain airborne particles
and help to reduce the dissemination of characteristic waste
odours.
INITIAL LAND CLEARING WORKS
This includes the removal of natural vegetation (clearing and stump removal) by cutting
trees, grass, bushes etc. and scrapping off the vegetation layer on operational areas
such as the landfill area that will receive domestic and public waste and the effluent
treatment plant area, wherever possible preserving landscape composition elements
even if this does not appear in the plans.
215
EARTH WORKS
Earth works should rigorously respect the plans for them and excess material from
cuts should be stored in an appropriate place to be used in the future as cover material
for landfill cells.
Layers that need to be compacted should be dampened until “ideal humidity” is achieved.
Earth works finish with the organization of the storage area for materials, which should
ideally be located close to the landfill operational area.
ACCESS AND SERVICE ROAD WORKS
Sanitary landfill access roads are categorized as external or internal and permanent or
temporary.
As has been previously explained, special attention has to be paid to the surfacing of
external access roads and their capacity to support heavy vehicles right from the stage
when alternative sanitary landfill sites are being evaluated. These roads have to be
easily passable in all seasons of the year and must have appropriate surfacing and
road signs so that they are safe for the heavy vehicles that will use them and for the
local residents. Road maintenance should be a priority in planning for the entire projected
operational life of the sanitary landfill in order to ensure the regular flow of collection
vehicles to the landfill and, therefore, sound sanitary and environmental conditions.
Internal access and service roads should be built with a primary surface of gravel or
selected rubble. They should have a uniform incline towards one side to direct rainwater
to a drainage system that runs along the side of the road.
In smaller landfills internal roads can have different types of surface: brick dust, gravel,
construction rubble or quarry products.
The recommended thickness for a landfill’s internal road surfaces is from 30 to 50cm,
compacted in layers of 15 to 25cm, depending on the volume of traffic and therefore
the landfill’s size.
WATERPROOFING WORKS
A 3m layer of clayey soil (k<10-7cm/s) between the bottom of the landfill and the top
of the water table provides an excellent protection against the contamination of
underground water. As a naturally occurring formation of this type is quite rare, a
technical solution that may be applied is the use of geo-membrane (plastic membrane)
lining to waterproof the bottom of the sanitary landfill.
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13. Solid waste final disposal
The bottom of the domestic waste sanitary landfill should be waterproofed immediately
after removing the superficial layer of soil from the operational area and this work
consists basically of laying the high density polyethylene (HDPE) membrane on the
compacted clayey soil. Once this geo-membrane is installed, it is covered with a layer
of earth to protect it against perforation and cutting by materials contained in the
waste.
Once the waterproofing work is completed the network of leachate collection pipes
should be laid. The passing of the leachate collection pipes through the plastic membrane
is done by means of a special union already incorporated in the membrane that is
soldered to the body of the tube.
The soldering of the membrane sections should be done by a specialized team and it
is recommended that the supplier provides this service.
In some cases, such as smaller sanitary landfills or where soil conditions are relatively
favourable and underground bodies of water are deep, the bottom of the landfill can
be waterproofed with an at least 80cm thick layer of compacted clay with a
permeability coefficient of less than 10-6cm/s. The viability of this solution should
be verified by specific technical studies carried out by the project management and
its approval depends on compliance with the relevant environmental body’s regulations
and norms.
DRAINAGE WORKS
“Water does not enter a landfill plot from outside or come out from inside of it without
being controlled.”
This principle requires the installation of three drainage systems for liquids:
Peripheral interception drainage that stops rainwater entering the landfill and
contaminated water exiting it;
Landfill bottom drainage leading effluent and contaminated water to the treatment
unit;
Superficial drainage installed during the operational stage minimizes rainwater
infiltration and consequently reduces the flushing of contaminants, the quantity of
effluent and the anaerobic reaction in the mass of buried waste.
Access roads (permanent or temporary) have their own drainage systems that also
serve service roads.
Whenever possible rainwater drainage should be through ditches lined with cement
soil, grass, etc. to avoid the use of buried pipes. The collection of percolated
leachate should be done through pipes laid on the waterproofing layer at the bottom
217
of the landfill in a zigzag pattern, with secondary pipes that conduct the collected
leachate into the main pipe. The liquid flows to a storage pit from where it is pumped
to a treatment plant, see figure 121.
These pipes should be bedded on gravel or crushed stone (blind drainage) and covered
by large grain, and then medium grain sand in order to avoid the silting of the pipes by
solids suspended in substantial quantity in the leachate. Geo-textile membranes can
be used instead of the layers of sand. This system is the most frequently used for a
sanitary landfill’s secondary drainage lines.
A more effective alternative is to install a Poly Vinyl Chloride (PVC) or HDPE perforated
tube in the gravel bed. The whole, formed by the pipe and the gravel, should be wrapped
in geo-textile membrane to avoid silting. This is used for the sanitary landfill’s principal
percolated liquid drainage lines.
See enlargement
PVC pipe
Effluent treatment
unit (ETU)
Secondary drainage pipe
Pumping
unit
Collection pit
1.5m
30m
PLOT 1
60m
PLOT 1
PLOT 2
PLOT 2
Secondary drainage pipe
Principal drainage pipe
L
Pumping unit
PVC pipe
LANDFILL
Bidim ®
Principal
drainage pipe
Collection pit
To ETU
LANDFILL
Percolated liquid minimum level
Sumergible pump
HDPE membrane
Figure 121 - Leachate drainage system
218
PVC pipe
Clay protection layer
13. Solid waste final disposal
The following figure shows cross sections of these two types of underground pipe.
Figure 122 - Types of underground leachate drainage pipe
INSTALLATION OF EFFLUENT
TREATMENT SYSTEM
The determination of the best leachate treatment system and its dimensions for a particular
landfill requires a previous study of the characteristics of the actual effluent generated in
the sanitary landfill. This circumstance does not prevent, but on the contrary requires, the
inclusion in the sanitary landfill project of an initial treatment facility (for at least primary
treatment) and a final monitoring lagoon before discharge into the receptor body.
The effluent treatment process can be biological, physico-chemical, physical, thermal
or a mixture of these (combined processes).
A low cost process that can be used is the recirculation of the effluent through the mass
of buried waste, the decomposition of which tends to intensify with the addition of micro
organisms contained in the effluent. At the same time the mass of waste functions as a
filter, reducing the contaminating potential of the re-circulated effluent. Another advantage
is the reduced volume of effluent to be treated due to evaporation by sun and wind.
This stage of effluent treatment system works should therefore include at least the
installation of a leachate recirculation system, storage pit and primary treatment plant.
219
Figure 123 – Leachate treatment lagoon
CONSTRUCTIONS WORKS
Construction works include the foundations and superstructure of support buildings
and the treatment plant.
Before works commence it is very important to check the location of these buildings
again as this is the last opportunity to modify plans, adapting them to some condition
of the site that may have been overlooked during the formulation of the master plan.
As in all works of a certain size, adjustments often have to be made due to difficulties
that arise on site, for example modifications in the route of internal roads may be
necessary where they are incompatible with the location of support units.
Any modification or adjustment of the plan should ideally be made by the planning
company, or at least it should be consulted, because it holds all the information and
technical specifications covering the overall context of the work. It is recommended
that the planner is on site during construction work.
ELECTRO-MECHANICAL
INSTALLATIONS
The assembly of the weighbridge should meticulously follow the manufacturer’s
instructions and the weighing platform should be perfectly level. Once installed the
weighbridge should be officially calibrated in the presence of the supervision team.
It is obligatory that a weighbridge is mounted on pillars so that the weighing platform
does not settle and therefore remains level.
220
13. Solid waste final disposal
DIGGING OF ENVIRONMENTAL
MONITORING WELLS
At least three monitoring wells should be dug, one upstream and two downstream
from the sanitary landfill operational area, incorporating the elements shown in figures
124 and 125.
Surface water should also be monitored at different points along any nearby body of
water upstream and downstream from the sanitary landfill area of influence.
Flow of
underground water
Landfill
Watercourse
Operational
area
Monitoring well
Surface water sample
collection points
Figure 124 - Location of environmental monitoring wells
Protecting
structure
Thread cap
Cover
Internal lining
(Ø 4” rigid PVC pipe)
Padlock
Sanitary
Protection slab
protection Sanitary seal
Ø Hole 8”
Ø Pipe 4”
Filling (impermeable
material: clay,
excavated earth)
Cement seal
WT (Water Table)
Pre-filter (washed
sand or quartz gravel)
5.00
Fixed cap
(pressure or thread)
Perforated or
grooved pipe
Impermeable layer
Figure 125 - Outline cross-section of a monitoring well
221
COMPLEMENTARY WORKS
Finishing works on the landfill site, including landscaping and general cleaning work.
Depending on the location of the landfill, the acquisition of materials and machines
can present difficulties. Construction materials should be bought from traditional market
suppliers that are if possible located close to the site.
Arrangements should be made so that machines and vehicles necessary for particular
tasks arrive on the site in accordance with the work schedule.
13.3.5 Sanitary landfill operation
Once the installation work is finished and the operational authorization has been
obtained, the sanitary landfill can begin receiving loads of waste in accordance with
the pre-established operational plan.
The operational plan should be simple and cover all the routine activities carried out at
a sanitary landfill while at the same time making provisions for their safety.
The basic activities carried out at a sanitary landfill are listed below:
WASTE RECEPTION CHECKING
On entering the landfill site the collection vehicle goes directly to the weighbridge
where it is weighed and all the information relating to its load is registered. If there is
no weighbridge, the vehicle goes to the entry checkpoint where the responsible person
writes down data identifying the truck and its load, including an estimate of its weight
(or volume). The vehicle then goes to the operational area to unload the waste it is
carrying.
LANDFILL OPERATIONS
When the construction method for a landfill is being determined, three main factors
have to be taken into account:
222
!
topography;
!
soil type;
!
water table depth.
13. Solid waste final disposal
In general there are three possible methods of construction and the choice depends
on the concept behind the particular sanitary landfill project and, in the last analysis,
the site conditions. The construction methods are:
Trench or ditch method – this is the most appropriate technique for land that is flat
or has only a slight incline and where the water table is relatively deep.
Figure 126 – Trench method
Ramp method – this is appropriate where the landfill site is flat, dry and with a type of
soil suitable for use as waste covering material. A natural embankment against which
cells can lean inspires the name of this construction method.
Figure 127 – Ramp method
Area method – this is the most appropriate technique for a completely flat site and
begins with a berm (artificial embankment) of clayey soil against which the first cells of
waste lean. Subsequently procedures are the same as for the ramp method.
223
BERM
RUBBISH
1st Cell
2nd Cell
Figure 128 – Area method
Solid waste disposal processes are almost identical in the three methods.
The basic rules of operation for a sanitary landfill are:
!
the distribution and compaction of waste should be done if possible from the bottom
to the top to achieve better results;
!
to obtain good compaction the waste should be distributed in not very thick layers
and a bulldozer should pass over the mass of waste of each layer three to six
times;
!
the height of the cell should be between four and six metres to provide optimum
decomposition conditions for the buried waste;
!
the usual incline of operational slopes is one metre of base for each metre of
height in an active cell and three metres of base for each metre of height in a
finished cell;
!
the ideal thickness of the coverage soil layer is between 20cm and 30cm for the
daily covering of waste;
!
the final layer of covering material should be at least 50cm thick;
!
the cell should be as narrow as possible but wide enough to allow the simultaneous
unloading of a certain number of trucks depending on the sanitary landfill’s capacity
(or the demands of collection) so that queues do not form and collection is not
delayed.
The procedures to be followed for each cell in each of the operational plots of the
sanitary landfill, on each of the levels (superimposed layers) are:
!
prepare the work face, including a truck manoeuvring area with primary surfacing
that is big enough for trucks to unload their waste and make the necessary turning
manoeuvres to return;
!
with a provisional 20cm thick layer of soil cover the top of the cell, with an incline
of 2% towards the edges, and the internal slopes;
!
224
cover the external slopes with the definitive 50cm thick layer of clay;
13. Solid waste final disposal
!
some days before completing cell 1, prepare the work face for unloading waste
into cell 2 in the same way as for cell 1;
!
as cell 1 is being filled the gas venting system should be progressively built into it;
!
repeat the operations for filling each cell and preparing the next one until plot 1 is
entirely filled;
!
repeat the same operations to fill plots 2, 3 and so on until the lower level is
completed;
!
fill cell 1 of the upper level following the same operational sequence used on the
lower level;
!
when burying the cells of the last level, make the final coverage of the completed
cells with a layer of 50cm thick compacted clay, with an incline of 2% towards the
edges;
!
repeat the sequence of operations until all plots on all levels are completely filled.
EFFLUENT TREATMENT
The main characteristic of sanitary landfill effluent is its changing composition over
time, due to progressive exhaustion of the biodegradable organic matter. Consequently,
the high contaminating potential of “new leachate” gradually reduces over a period of
ten years to a point when it does not need treatment.
Table 24 shows the range of parameter variation for some sanitary landfill percolated
liquids in Brazil and is presented here as an example of the difficulties involved in a
definitive pre-establishment of the type of effluent that will be produced in a particular
sanitary landfill. These difficulties arise because the type of effluent produced depends
on the particular characteristics of the waste (determined by its component substances)
deposited in the landfill and on a series of specific factors that influence the
decomposition process in the mass of organic waste.
Table 24
Range of leachate composition variation
Parameters
pH (un.)
Range of variation
Minimum
Maximum
5.9
8.7
15.0
3,140.0
Nitrate Nitrogen
0.0
5.5
Nitrite Nitrogen
0.0
0.1
Ammoniacal Nitrogen
6.0
2,900.0
966.0
28,000.0
Total Kjeldahl Nitrogen
COD
225
Table 24 (cont.)
Parameters
Range of variation
Minimum
Maximum
480.0
19,800.0
50.0
11,000.0
Sulfates
0.0
1,800.0
Total Phosphorus
3.7
14.3
Copper
0.0
1.2
Lead
0,0
2.3
Iron
0.2
6,000.0
Manganese
0.1
26.0
Zinc
0.1
35.6
Cadmium
0.0
0.2
Total Chromo
0.0
3.9
Faecal Coliform (un.)
49.0
4.9 x 107
Total Coliform (un.)
230.0
1.7 x 108
BOD5
Chlorides
Source: Data compilation, COMLURB (Rio de Janeiro, Brazil), 1993.
Note: all values are in mg/l, except where another unit is indicated.
The volume of percolated liquid produced by a sanitary landfill registers seasonal
variations depending on climatic conditions in the region and the local drainage system.
It is influenced by temperature, rainfall quantity, evapotranspiration, the nature of the
cell coverage material and in particular its permeability, the vegetation cover on the
sanitary landfill area, and many other factors.
A way of calculating the potential flow of effluent from a new sanitary landfill is by
direct correlation with percolate generation data obtained from measurements in similar
but already operating landfills located in regions with similar climatic conditions. However
distortions may occur.
Another procedure is the “Swiss method” that calculates the flow of sanitary landfill
percolated liquid by means of an equation involving the dimensions of the operational
area, the annual rainfall and a factor determined by characteristics of the land. Another
more complex procedure calculates the production of sanitary landfill percolated liquids
through the water balance.
Stabilization lagoons
One of the most frequently used forms of treatment involves lagoons into which
leachate effluent is discharged after passing through a grate or a mechanical sieve and
226
13. Solid waste final disposal
remaining for at least 24 hours in an equalization tank to homogenize its composition
as much as possible. The following figure presents an outline of a typical leachate
treatment system employing aerobic lagoons.
Percolate
drainage
Equalization
tank
Grates
Sanitary
landfill
First aerobic
lagoon
Overflow
outlet
Second aerobic
lagoon
Finishing
lagoon
Receptor
body
Figure 129 - Treatment in aerobic lagoons
It is recommended that a superficial aeration device is installed in the equalization tank
to improve the homogenization of the liquid mass and the aerobic condition of the
effluent to be treated.
In general aerobic stabilization lagoons have the following basic characteristics:
!
form – truncated pyramidal;
!
depth – 1.5 metres;
!
retention time – 25 days minimum.
Entry to the lagoons should be through a two pipe system to improve the flow of
effluent in the lagoon avoiding dead zones and short cuts. The height of the effluent
overflow outlet should be adjustable to ensure that leachate remains inside the lagoons
for the minimum required time irrespective of the flow volume.
This series of lagoons ends with a smaller one where the effluent receives a finishing
treatment. This lagoon is also aerobic and has the same physical characteristics as the
previous ones but only retains the effluent for seven days.
Lagoon borders should be treated so that no vegetation grows in the air-effluent
intermediate zone, as such vegetation could harbour mosquitoes and other vectors.
In addition, sludge should be periodically removed so that the effectiveness of the
treatment is not impaired.
227
This removed sludge should be put to dry in a drying bed and then deposited in the
sanitary landfill, while the liquid can be directly discharged into the receptor body.
In determining the type of treatment to use the more correct procedure is a laboratory
study of the effluent’s characteristics. It is not advisable to use only documented data
to calculate the necessary dimensions of a treatment unit.
Effluent flow measurement should be carried out at a minimum of two points on the
treatment system:
!
immediately after the storage pit or immediately before the equalization tank
!
immediately before the point of discharge into the receptor body
Gross effluent and treated effluent should be periodically monitored.
Recirculation
Another commonly used treatment of sanitary landfill percolated effluent is its
recirculation through the mass of waste using sprinklers, tank trucks or infiltration
beds.
In this process the effluent gradually looses its toxicity (basically its organic content)
due to airing and the biological action of micro organisms present in the mass of waste.
In addition part of the re-circulated effluent evaporates and to encourage this sprinkler
nozzles should be adjusted to produce a fine spray, thus increasing the rate of
evaporation.
Evaporation is an important factor in leachate recirculation and it functions better in
regions with a negative water balance, that is, regions where the rate of evaporation is
higher than that of rainfall. It can also be used in other regions during dry seasons as
an auxiliary procedure complementary to the principal method being used.
Another important aspect to consider is that the leachate storage pit should have
enough capacity to store a sufficient amount of liquid for the recirculation pump not
to have to be used at very short intervals.
Ideally the pit should be designed to hold one complete day’s production of leachate
during the rainy season, thus making it possible for recirculation to take place only
once a day and preferably during the eight hour period that the operator is present at
the sanitary landfill.
The disadvantages of this process stem from its high electricity consumption together
with its dependence on a constant supply of electricity and the functioning of the
pump. If the electricity supply or the recirculation pump fail, gross effluent will inevitably
drain into some body of water producing environmental damage.
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13. Solid waste final disposal
Ideally recirculation should serve as a complementary procedure to one of the
conventional effluent treatment processes, such as stabilization lagoons or an activated
sludge system.
The following figure shows a recirculation system using infiltration beds.
Suction
pit overflow
Drainage valley
Service roads
Submergible pump
Ditch for percolated liquid
Recirculation area
Pumping pipe
PVC Ø 02”
Perforated PVC
pipes Ø ½”
Landfill
Suction pit
Landfill
Nº 2 gravel
beds
Ditch for percolated liquid
Figure 130 - Infiltration bed recirculation
Activated sludge
Other processes that can be used in the treatment of sanitary landfill percolated liquids
are the activated sludge system and evaporation.
In the activated sludge system effluent passes through a preliminary treatment generally
in the form of a chamber with bars after which it is directed to a primary settling tank
where solids settle. It then goes to an aeration tank where aerators, usually on the
surface, inject air into the liquid mass allowing the aerobic bacteria to stabilize the
organic matter, which generates a secondary sludge that remains in suspension.
The effluent from the aeration tank passes to a secondary settling tank where the
previously generated sludge precipitates. A part of that sludge then returns to the
aeration tank while the settled sludge is put together with the sludge from the primary
settling tank and goes to a drying bed. The dried sludge is taken back to the landfill for
disposal.
From the secondary settling tank the liquid part goes to a finishing lagoon similar to
the one at the end of the aerobic lagoons process, from where it is discharged into
the receptor body.
229
Primary
settling tank
Aerators
Preliminary
treatment
Aeration
tank
Secondary
settling tank
Finishing
lagoon
Receptor
body
Flow
measurement
Figure 131 - Activated sludge
Evaporation
In the evaporation process effluent is sent to a metal tank, the evaporator, where it is
heated to a temperature of 80ºC to 90ºC causing part of the liquid to evaporate and
consequently the effluent to become more concentrated.
The hot vapour leaving the evaporator passes through a filter that retains humidity and
then goes to a final heating chamber from where it is discharged, dry, into the
atmosphere.
The sludge, now more dense with 30% of it being solid material, comes out through the
lower part of the evaporator and is disposed of in the landfill.
The great advantage of this process is its low operational cost as the fuel used to
evaporate the effluent is biogas from the sanitary landfill itself.
Treated air outlet
Burner
T= 80ºC to 90ºC
Percolated
liquid inlet
Evaporator
Temperature
of departing
air 750ºC
to 900ºC
Biogas
inlet
Concentrated
sludge
Sludge outlet
Thermal
lining
Chimney
Humidity
filter
Sludge
pump
Average concentration
30% solid
Supporting base
Figure 132 - Leachate evaporator
230
Biogas
inlet
Combustion
air
13. Solid waste final disposal
Whatever treatment option is selected, treated effluent should meet all discharge
standards established by the environmental control body.
RAINWATER DRAINAGE SYSTEM
The rainwater drainage system should be kept clean and free of obstructions, particularly
underground conduits.
As the sanitary landfill is constructed with solid waste, comprising mostly organic matter,
the decomposition process that gradually takes place in the mass provokes frequent
settlings of the surface.
It is important to constantly make adjustments to the system accommodating to these
movements in the mass of the landfill, at its edges, and on the slopes, in order to
promptly correct potentially damaging effects on the rainwater drainage devices.
GAS VENTING
The gas venting system comprises vertical wells surrounded by gravel or gross ground
stone, located at a distance of 50m to 60m from each other.
There are two methods for installing a gas drainage system: extending the pipe as the
landfill evolves (recommended) or excavating the completed cell to install the pipe. In
both cases the pipe should be high enough to serve as a guide for its further extension
when work begins on the next level up.
Once the well is installed, the ground around it should be covered over a radius of
approximately two metres with a 50cm thick layer of clay to avoid the dispersion of
gas into the atmosphere.
A burner should be installed in the mouth of the well. The gas venting system should
be constantly monitored so that burners are always alight.
Figure 133 - Installation of gas drainage wells
231
ENVIRONMENTAL
MONITORING
The monitoring of water in the area surrounding the sanitary landfill should begin before
the commencement of its operational phase with the collection and analysis of samples
from nearby bodies of water and the water table. The quality of these samples is
evaluated so that they can be compared with future samples.
The second phase of environmental monitoring commences when effluent generated
by the sanitary landfill begins to be stored for treatment and gases begin to be produced.
The frequency of sampling and the parameters that are analyzed must comply with
regulations established by the environmental control body.
Example of an environmental monitoring program:
!
Monthly - physical, chemical and bacteriological analyzes of gross and treated effluent
in the treatment system, including tests for pH, BOD, COD, total and fixed sedimentary
residues and colimetry tests.
!
Every three months - analysis of water from the monitoring wells and from water
body sampling sites both upstream and downstream from the sanitary landfill,
analyzing results for the same parameters in each case.
GEOTECHNICAL AND
TOPOGRAPHICAL MONITORING
At all times during the filling of sanitary landfill cells attention must be paid to
topographical alignment, up to and including the creation of the final covering surface
incline. Careful attention should also be paid to topographical aspects in determining
the incline of percolated liquid drains to ensure optimum drainage conditions after
collection.
In addition to these considerations, concrete frameworks should be installed in the
work faces for the purpose of monitoring the differential settling of the buried layers.
These frameworks should be read monthly, and the frequency of readings should be
increased when significant settling is observed. The reading of these frameworks will
also be useful to monitor the geotechnical stability of the sanitary landfill through the
measurement of horizontal displacement.
13.3.6 Equipment
Commonly used machines and vehicles for the operation of a sanitary landfill are:
!
bulldozer - for the distribution, compacting and covering of waste;
!
dump truck - for transporting coverage material and material for surfacing internal
access roads;
232
13. Solid waste final disposal
!
mechanical loader - to load trucks;
!
mechanical digger - for digging and maintaining drainage ditches;
!
tank truck – to supply water for reducing dust on internal roads and dampening
lighter waste (papers, plastics, etc.) to avoid it being scattered.
Factors that have to be taken into account when selecting machinery are: the availability
of financial resources, specialized labour for maintenance and spare parts for immediate
delivery. The sanitary landfill’s operational method is the principal factor that determines
the selection and dimensions of machinery needed for landfill operations.
As this equipment represents the most significant operational expenditure for a sanitary
landfill, a rigorous system controlling its use should be established not only in relation
to the number of hours that machines are operating for, and the wear and tear on
their components, but also in regard to their correct operation during daily tasks in
order to optimize their use and minimize unproductive procedures.
13.4
Controlled landfills
With everything that has been previously explained about sanitary landfills, from the
planning and installation phase to the final disposal of urban solid waste, the extensive
range of technical components involved in them can be appreciated as can the amount
of resources that it is necessary to allocate, not only for installation but also for their
ongoing operation in compliance with all the technical requirements and applicable
regulations.
In Latin American and Caribbean countries the limited availability of public resources
and the great demands made upon them create a situation in which it is very difficult to
establish sanitary landfills, to such a degree that only a few municipalities can install
them. In addition, even when the necessary financial resources are available for
installation there can be difficulties in obtaining sufficient resources and qualified labour
to operate a sanitary landfill in a way that meets its rigorous technical requirements.
Nevertheless, in spite of all these obstacles it is necessary to deal with the problem of
solid waste disposal as it has such serious consequences for sanitary and environmental
conditions in cities. In this context the alternative “controlled landfill” option arises, a
type of landfill that is often misunderstood or badly defined even by the technical
community itself. Such definitions tend to focus on specific aspects of particular
projects rather than providing a wider conceptual description.
The most appropriate definition of a controlled landfill is:
“A controlled landfill is a modified version of a sanitary landfill where the rigorous
technical requirements applicable to the latter are more flexible in order to facilitate
urban solid waste final disposal on the ground, with the waste duly isolated and covered,
233
complying with minimum sanitary control requirements through the selection of a site,
the natural characteristics of which minimize the risk of negative environmental impacts.”
The key to a successful controlled landfill project is therefore the choice of the land
where it will be installed, the principal characteristics of which should be: soil that is
not very permeable (clayey) and a deep water table (at least 3 metres below the level
of the natural land).
Where the soil type is not appropriate the controlled landfill project should make
provision for the installation of an at least 50cm thick waterproofing layer of clayey
soil brought from the nearest deposit.
The cells of a controlled landfill are also built with compacted layers of waste but
without necessarily using specialized machines (bulldozers, self-propelled waste
compactors), that is, waste can be manoeuvred using lighter equipment or manual tools,
though it must be routinely covered with earth.
It is common for controlled landfills to be used in small cities that collect up to 50 tons
of solid waste per day and where municipalities are not in an economic condition to
maintain, for example, a bulldozer exclusively and permanently allocated to final waste
disposal, or to implement, operate and maintain some of the systems required by the
norms that regulate sanitary landfills.
Of these systems it is the absence of effluent treatment that causes such municipalities
most problems. Consequently special care should be taken with the rainwater drainage
system of controlled landfills, as the more effective that system is the less effluent
will be produced in the landfill. In this respect it is also important that the waste coverage
layers are of clayey earth and particular attention should be paid to the top covering
when the landfill reaches its maximum height.
There is no exact definition of a “controlled landfill”, as they vary from very simple
installations to ones that are similar to sanitary landfills. A controlled landfill offers
municipalities with limited investment and budgetary capacity a relatively immediate
opportunity to operate a low cost urban solid waste disposal system that eliminates
the environmental and social aggression of refuse dumps, and in doing so demonstrates
the principle “the ideal can be the enemy of the good”.
Upper waterproofing
Controlled landfill
Lower waterproofing
Maximum
water level
Flow of
underground water
Impermeable soil
Figure 134 - Cross section of a controlled landfill
234
h>3.0m
Water table
13. Solid waste final disposal
One of the requirements for a sanitary landfill is the permanent presence of specialized
machines for the manoeuvring, compaction and covering of waste. This is not a realistic
possibility for most small-sized municipalities in Latin America and the Caribbean with
their budgetary limitations and the significant under use of equipment that this would
imply due to the relatively small amount of waste to be disposed of, as well as the
drain on equipment resources needed for other municipal services.
For such municipalities a controlled landfill allows for alternative solutions such as the
periodic and programmed use of machines from other municipal sectors - for example
those used for road maintenance - in the preparation of the weekly work face.
A mechanical digger for example could excavate trenches for future waste cells where
the land type permits the employment of this method of solid waste landfill construction.
In such a case resultant material would be stored in a nearby place for later use in the
covering operation. A practical alternative for small-sized municipalities is to use easily
obtainable manual tools for landfill operations. In this case additional compaction can
be achieved by collection vehicles being driven over filled areas as the cell advances.
When it is not possible to guarantee even the infrequent programmed availability of
machines to do the heavier work involved in landfill routines (such as excavating earth),
the selection of the site becomes fundamentally important for an effective functioning
of the controlled landfill. The ideal in such a case is a small dry natural hollow.
Manoeuvring and coverage work is done manually as described below.
The waste can be manoeuvred and the top surface and lateral sloped (1:1) surfaces
can be levelled using hoes, mallets, rakes, pitchforks and forks.
The covering of waste should be done at the end of each working day.
Waste compacting can be done with mallets.
An entirely manual operation is recommendable only for a daily waste volume of up to
40m³ or approximately 10 tons.
Figure 135 - Manual compaction of waste in a cell
235
Where a landfill is manually operated it is indispensable that workers engaged in the
manoeuvring and covering of waste have, in addition to the appropriate tools, clothing,
shoes and gloves that guarantee their protection and safety. On rainy days they should
wear plastic waterproofs.
13.5
Environmental recuperation of refuse dumps
As has been explained, a refuse dump is an inappropriate form of urban solid waste
disposal as it produces a series of negative environmental impacts and poses sanitary
risks for the population.
Areas degraded by refuse dumps should therefore be recuperated by containing such
impacts and re-establishing healthy conditions there.
Theoretically the correct way to recuperate land degraded by a refuse dump is to
collect all the waste inappropriately disposed of there and transfer it to a sanitary
landfill, subsequently recuperating the excavated area by filling it with natural soil from
the region. In practice however this procedure is not usually economically viable and in
most cases it is anyway impossible to implement due to the physical characteristics of
the dump site.
It should be noted that the strategic context of a refuse dump environmental
recuperation exercise can be:
!
that the area will be recuperated after it is closed for the dumping of waste, or
!
that the area will be recuperated in such a way that it will be able to continue receiving
waste but on a sound sanitary and environmental basis.
An analysis of these alternatives is fundamental to appropriate planning for future
solid waste final disposal. It is always recommended, especially in cities with restricted
financial resources, that investment in the environmental recuperation of a dump is
combined with the creation of disposal service and environmental protection
infrastructure in the same place, thus allowing for the continued disposal of waste
there but in sanitary conditions.
In this way the municipality can avoid generating negative impacts on a virgin site before
exhausting the waste disposal capacity (useful life) of the area previously used as a
refuse dump. Another aspect to consider is the availability of resources. Often a
municipality does not have access to sufficient finance for carrying out two works,
that is, the recuperation of the degraded refuse dump area and the installation of a
new final disposal system on another site, so it will naturally opt for undertaking the
latter and leave aside remedying the environmental liability incurred by the refuse dump.
Therefore whenever possible the refuse dump site or neighbouring land should be
used to install a new final disposal system, in order to optimize the use of resources
and maximize sanitary, environmental, technical-operational and economic results.
236
13. Solid waste final disposal
When a refuse dump is permanently closed, thus ending any type of waste disposal
there, and site recuperation is undertaken, the basic procedures are:
a) if there is no reliable cadastral data, previous urban cleaning personnel should be
consulted to determine as precisely as possible the extent of the area affected by
waste and the principal physical characteristics of the natural land;
b) delimit the affected area in situ;
c) carry out probes to measure the thickness of the layer of waste throughout the
degraded area;
d) remove the waste from the parts of the site where the layer of waste is thinner (in
general less than one metre) and deposit it on the part of the refuse dump where
the layer of waste is thickest;
e) form lateral slopes with an appropriate incline, in general 1:3 (V:H);
f) give the top surface an incline as indicated in the section on drainage;
g) after they have been levelled, cover the exposed waste surfaces with an at least
50cm thick layer of good quality clay, including the lateral slopes;
h) recuperate the excavated area by filling it with natural soil from the region;
i) install rainwater and leachate drainage devices appropriate for the particular project;
j) dig one or more storage pits for effluent collected by the leachate drainage devices;
k) construct vertical wells for gas venting;
l) spread a layer of top soil over the layer of clay on the top surface and slopes;
m) sow grass and native plant species with short roots;
n) use three of the previously made probe holes to install water table monitoring
wells: one on the upstream side of the area of the recuperated dump and two on
the downstream side.
The recuperation of a refuse dump does not finish with the implementation of these
procedures. Leachate that accumulates in the storage pits should be periodically recirculated in the mass of waste, through sprinklers (similar to those used for grass
watering) or infiltration beds; gas vents should be periodically checked so that those
extinguished by wind or rain can be relit; and the quality of underground water should
be checked through the monitoring wells, as should the surface water in nearby bodies
of water.
237
As has been previously explained, due to the difficulty of finding new sites appropriate
for sanitary landfills, whenever possible a recuperated dump site should continue to
be used, but as a landfill. In this case, the sequence of procedures listed in the previous
paragraph is modified after point “g” in the following way:
!
prepare the excavated area to receive more solid waste, waterproofing it with good
quality clay and installing underground pipes to collect leachate;
!
install the necessary rainwater drainage channels to stop rain water run off reaching
future work faces;
!
excavate one or more storage pits for effluent generated in new cells;
!
as the landfill evolves build vertical wells for gas venting;
!
establish procedures for distribution, compaction and covering as if it were a sanitary
landfill;
!
install a leachate recirculation system and (depending on the climatic conditions of
the zone) an effluent treatment system with stabilization lagoons;
!
dig water table monitoring wells, one upstream and two downstream from the future
operational area.
13.6
The situation of segregators
In the present situation of Latin American and Caribbean countries there are not enough
employment opportunities in the formal work market to allow universal entrance into
it by a growing population, which together with low work training levels leads people
to seek any activity that at least provides a means of survival for themselves and their
families.
Even though recyclable waste segregation in refuse dumps and streets is an unhealthy
activity, it has become an “alternative job” as a result of the now endemic large-scale
social crisis.
Segregators tend to circulate freely in the operational area of a refuse dump, together
with collection trucks and scrap dealers, and such activity hinders distribution,
compaction and covering operations, in addition to creating a serious risk of accidents
involving the working machines and vehicles.
Even more serious is the presence of children at dumps, either due to a lack of
alternative options for parents who do not have anybody to take care of them while
they are engaged in segregation work, or because the children themselves are
segregating materials in order to increase family income.
Refuse dump recuperation projects are therefore not limited to engineering issues
but also have to solve a complex social problem that cannot and should not be the
sole responsibility of the body providing urban cleaning services, but rather requires
articulated action involving various governmental sectors.
238
13. Solid waste final disposal
Some of the initiatives that should be implemented to gradually change this situation
are the development of alternative income and employment programs (such as
segregator cooperatives, for example), the provision of technical training for
segregators so that they can engage in other activities in the formal labour market,
cooperation with non-governmental institutions and private companies, programs that
provide children with integral fulltime places in schools or sports and recreational
centres and a compensatory system for parents whose children cease to engage in
segregation work.
Figure 136 – Recycling plant operated by a segregator cooperative
13.7
Special domestic waste disposal
13.7.1 Construction rubble disposal
As has been explained in the chapter on solid waste treatment, the ideal destiny for
construction rubble is recycling.
However when a municipality does not have this option, it is disposed of at the bottom
of a landfill.
Disposing of construction rubble in a sanitary landfill is not economical as it is inert
waste that is being deposited in a specialized system surrounded by technical resources
designed to protect the environment, when it could be disposed of in more simple
landfills at a lower cost.
Depositing this type of waste in a sanitary landfill is also not economical from an
environmental perspective as the useful life of the landfill will be diminished by waste
that, with effective management, could be used for the recuperation of excavations
resulting from the extraction of materials used in the construction industry.
239
The only appropriate types of rubble disposal in a sanitary landfill are:
!
its use as base material for internal roads and unloading areas;
!
its use for the temporary covering of urban waste when there is a scarcity of the
usual covering material in the zone.
13.7.2 Disposal of batteries
As used batteries constitute hazardous waste, particularly due to the presence of
heavy metals in their composition, their final disposal should be managed with the
same criteria as are applied to industrial waste that carries the same type of risk.
Before organizing a system for battery separation at source, with a view to recycling
or another form of treatment and final disposal, the body responsible for urban cleaning
should ensure the participation of producers, dealers and other players in this economic
sector, who should be responsible for financing such a process.
This waste should be regarded as waste from the industrial process of its producers,
who should therefore be responsible for its collection, treatment and final disposal.
Corresponding regulations should be brought into force in support of this type of
model to avoid the risk that the municipality will be left with responsibility for costs
associated with production process waste from private sector enterprises.
Two initiatives are presented below as examples of measures that the private sector
can adopt for the collection and final disposal of batteries.
!
develop a project together with associations of authorized technical service
providers for the installation of battery collection containers on their premises.
Batteries collected in this way would be removed once a month and taken to a
treatment or recycling site.
!
establish an agreement with mobile phone producers under which they set up a
discarded battery collection program that includes the provision of a telephonic
information centre providing the location of places where there are special containers
for used batteries.
13.7.3 Disposal of fluorescent tubes
Often small pieces of broken tubes are accidentally discarded together with common
waste in sanitary landfills.
However, as there is mercury in them the appropriate final disposal of such waste,
especially in large amounts, is in a landfill designed specifically for industrial waste with
this risk classification. In this case too the “polluter pays” principle applies.
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13. Solid waste final disposal
13.7.4 Disposal of tyres
When it is not possible to recycle used tyres or use them in cement industry furnaces,
for example, they can be disposed of in sanitary landfills after being ground so that
they do not cause structural problems in the landfill.
The body responsible for urban cleaning should not have to take on the problematic
final disposal of used tyres, which should be the responsibility of producers and
distributors as it is their economic activity that generates this waste.
In support of this current perspective on the problem national legislation is needed to
facilitate a progressive reduction in the quantity of such waste through a policy that
fosters recycling by the industry and suppliers.
Finally it is necessary to pay attention to the import of used but still usable tyres as
together with these goods the companies of exporter countries are also exporting
the problem of disposal when they are of no further use.
13.8
Disposal of waste from special sources
13.8.1 Industrial waste disposal
Soil bio-regeneration (land farming), industrial landfills, waste barrages and other forms
of disposal are commonly used for industrial waste.
SOIL BIO-REGENERATION
Soil bio-regeneration (land farming) is a biological treatment through which the organic
part of waste is decomposed by the micro organisms that live in the upper layer of
soil. This treatment is very much used for the final decomposition of oil by-products
and organic compounds.
The treatment consists of mixing and homogenizing waste with the upper layer of
soil (to a ploughing depth of 15cm to 20cm). Once the micro organisms complete
the degradation work, a new layer of waste can be treated in the same soil, repeating
the same steps, and so on. Although the same land can be used repeatedly the
disadvantage of this method is its need for large areas of land as the layers are not
thick.
The following figure shows an outline cross section of a bio-regeneration area.
241
Periodic application and
mixing of waste and soil
Containment of rainwater that
falls on the treatment area
Evaporation
200 m
Diversion of
rainwater that
falls outside the
treatment area
Water
course
Infiltration
Aerobic decomposition, absorption
and adsorption in the upper layer
Figure 137 - Soil bio-regeneration outline
INDUSTRIAL LANDFILLS
Industrial landfills are classified according to the hazard presented by the waste to be
deposited there. In Brazil, for example, landfills for Class I waste can receive hazardous
industrial waste; those for Class II, non-inert waste; and those for Class III, only inert
waste.
In any type of industrial waste landfill a rainwater drainage system and bottom
waterproofing are essential to avoid soil and water table contamination from rainwater
that has percolated through the waste, as demonstrated in the following figure.
Rain
Evaporation
Superficial drainage
Leaching
Waste
landfill
Leaching
Percolation
Maximum
water level
Flow of
underground water
Non-saturated
zone
Wastewater
Impermeable soil
Figure 138 - Flow of water in a landfill
In order to reduce the amount of effluent to be treated, the first step is to avoid, by
means of barriers and drainage ditches, the incursion of rainwater falling outside the
limits of the landfill that would otherwise increase the volume of effluent percolating
inside the landfill.
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13. Solid waste final disposal
The second step is waterproofing the bottom of the landfill with a plastic membrane in
order to stop leachate contaminating the soil and the water table.
The main disadvantage of an industrial landfill as a means of final waste disposal is that
it requires a large area of land in order to be economically and operationally viable and
it should be taken into account that the waste continues to be potentially dangerous
until it can naturally incorporate itself in the environment. In this context the best
course of action is to concentrate efforts on earlier stages, that is, on the reduction
of waste production and its treatment so that only unusable refuse is deposited in
industrial landfills.
An industrial landfill with a capacity of 15,000 tons requires an initial investment of
approximately two million dollars and involves operational costs of 50 to 150 dollars
per ton. The operational cost varies according to the waste’s degree of toxicity.
When operating an industrial landfill special precautions have to be taken to control
the type of waste unloaded there as only chemically compatible wastes can be disposed
of in any given landfill, that is, wastes that do not react in contact with each other or
with infiltrated rainwater.
The most common phenomena produced by the mixture of incompatible wastes are:
heat generation, fire or explosion, production of smoke and gases that are toxic and
inflammable, dissolution of toxic substances and violent polymerization. Consequently,
before waste is unloaded at the landfill the list of compatible wastes published by
environmental control bodies must be consulted.
Industrial landfill for Class I waste
Final coverage
layer
I = 2%
Rainwater drainage
h = 4 to 6m
Drainage
layer
t = 25cm
Waste
t = 20 to 30cm
Waste
Waste
t = 0.60 to 1.00m
Intermediate
coverage
(soil – t = 25cm)
Blind drainage
Physical
protection layer
t = 30cm
Vegetation
coverage
Pumping unit
Waste
Storage pit
I = min 0.5%
Plastic membrane
(double layer)
t =1.0 to 2.5mm
Plastic
membrane
Maximum
water level
h > 3m
To the effluent
treatment unit
PVC
tube
Leakage detection
layer (t = 25cm)
Figure 139 - Industrial landfill for Class I waste - typical cross-section
243
Industrial landfills for Class I waste require more rigorous waterproofing than those
for Class II and III. A minimum water table depth of three metres is required and the
following layers are compulsory:
!
double layer of bottom waterproofing: PEAD membrane and clay protection layer (k
< 10 - 7cm/s);
!
leakage detection layer between the bottom waterproofing layers;
!
top waterproofing layer;
!
drainage layer on top of the top waterproofing layer (t = 25cm).
Industrial landfill for Class II and Class III waste
Final coverage
layer
I = 2%
Rainwater drainage
h = 4 to 6m
Drainage
layer
t = 25cm
Waste
t = 0.60 to 1.00m
Vegetation
coverage
t = 20 to 30cm
Waste
Waste
Pumping unit
Blind drainage
Waste
Storage pit
I = min 0.5%
Plastic membrane
t = 0.8 to 1.5mm
Physical
protection layer
t = 30cm
Maximum
water level
h > 1.5m
To the effluent
treatment unit
PVC
tube
Figure 140 - Industrial landfill for Class II and Class III waste – typical cross-section
Industrial landfills for Class II and Class III waste are similar to domestic waste sanitary
landfills but do not usually have a gas venting system.
Beginning at least 1.5m above the highest level of the water table and going from
bottom to top this type of landfill usually consists of the following layers:
!
bottom waterproofing with PEAD membrane;
!
physical protection for the plastic membrane;
!
percolates drainage system;
!
layers of waste (from 4.0m to 6.0m thick) with 25cm thick layers of soil between
them;
!
although it is not obligatory, a top waterproofing layer of plastic membrane or good
quality clay (k = 10 - 6cm/s; thickness > 50cm) is recommended;
!
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25cm thick sand drainage (necessary only where there is top waterproofing);
13. Solid waste final disposal
!
organic soil (thickness > 60cm);
!
vegetation coverage with short root plant species.
The percolated liquid, collected through a drainage system similar to the one in the
previous figure, should be led to a treatment unit. The type of treatment depends on
the characteristics of the waste deposited in the landfill but usually a complete physicochemical process is applied, followed by a conventional biological process (stabilization
lagoons or activated sludge).
WASTE BARRAGES
Waste barrages are used for the disposal of liquid waste as well as sludgy waste that
has a humidity content of more than 80%. These landfills are not deep and cover an
extended area. They have a filtration and drainage system at the bottom (flute) to
collect and treat the liquid part while containing the solid matter inside the barrage.
Such barrage systems use a double layer of waterproofing only on the bottom. A top
waterproofing layer is not required as the surface serves to evaporate off part of the
liquid content.
After the closure of the landfill, when the top layer of waste has solidified, the surface
is waterproofed with a layer of clay to reduce rainwater infiltration and thus the need
for ongoing treatment of percolated liquids.
OTHER FORMS OF DISPOSAL
Highly hazardous waste can be disposed of in underground saline or calcareous caves,
or can be injected into exhausted oil wells.
13.8.2 Radioactive waste disposal
There are three final disposal processes for nuclear waste, all very expensive and
sophisticated:
!
construction of special shelters with double walls of high resistance concrete,
preferably underground;
!
encapsulation in an impermeable concrete covering followed by dumping in the
deep ocean (this process is very much criticized by environmentalists and in some
countries is prohibited);
245
!
disposal in saline underground caves that are sealed so as not to contaminate the
biosphere.
13.8.3 Port and airport waste disposal
In some countries it is required by law that port and airport waste is disposed of by
incineration. However, in many of these countries only some ports and airports comply
with such environmental legislation while in the others no special attention is paid to
waste disposal.
In recent years the sanitary vigilance authorities of several countries have begun to
implement measures that increase controls in ports and airports out of a concern for
the potential economic impact of diseases such as foot-and-mouth or mad-cow disease
being “imported” from other countries or regions.
Port and airport waste not at risk of being contaminated by contact with waste generated
in boats or planes arriving from areas with endemic diseases can be disposed of in
sanitary landfills. It is therefore essential that an effective and safe solid waste storage,
handling and internal transport system is implemented in order to avoid contact between
common waste and waste that is contaminated or represents a potential sanitary risk.
13.8.4 Medical waste disposal
The only final disposal process for this type of waste in the ground is the septic
trench, a method that is very much questioned by most professionals but, due to its
low investment and operational costs, is a viable option for cities with budgetary
limitations.
Conceptually a septic trench is in reality a Class II industrial landfill, as described in
13.8.1, which involves the daily covering of waste and obligatory waterproofing but no
leachate collection.
There are two types of septic trench: individual ones such as may be used by large
hospitals and ones that are annexed to a municipal sanitary landfill.
In the first type, trenches should be excavated with dimensions appropriate for receiving
waste generated over a pre-determined period (a month, six months or a year). The
bottom and sides of the excavated trench are then waterproofed and waste begins to
be deposited there, the surfaces of which should be covered daily.
Top waterproofing should begin as soon as the volume of waste reaches its final
height and should progress at the same rate as the filling of the trench.
When the septic trench is annexed to a municipal landfill, a distinct plot should be
separated for medical waste disposal. This plot should be fenced and isolated from
the rest of the landfill.
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13. Solid waste final disposal
The procedures for waste disposal and waterproof layer installation are similar to
those previously described.
Final
coverage
Drainage
layer
Plastic
membrane
Fence
Waste
Waste
Top
coverage
3m to 4m
Waste
Lateral slopes
coverage
Plastic
membrane
Figure 141 - Septic trench installed in a sanitary landfill
13.9
Sanitary landfills and carbon credits:
Opportunities to help resolve environmental problems
The environmental damage resulting from refuse dumps and irregular dumping always
causes significant problems for municipal administrations. The unpleasant appearance
and the bad odour that they emit discredit city administrations where waste is not
appropriately disposed of. From an environmental perspective dumps are a real calamity
as they contaminate the soil, the atmosphere, surface and underground water and
represent a potential source of epidemics and fires as well as being susceptible to
disintegration.
Many mayors have been held directly accountable by environmental bodies, auditing
tribunals and public prosecutors for poor urban cleaning management, especially in
relation to the final disposal of waste.
Attempting to resolve urban solid waste final disposal problems through the installation
of recycling or incineration plants is often not feasible as, in spite of spectacular
promotional offers by equipment manufacturers, they require significant financial
investment and their operation involves a high level of complexity, both of which are
beyond the capacity of municipalities that lack financial resources and specialized
personnel.
The simplest and cheapest option for solving the problem of refuse dumps is
undoubtedly the installation of sanitary landfills, provided they are well built and correctly
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operated. Sanitary landfills do not contaminate or emit unpleasant odours and after
their final closure they can be used for the construction of sports complexes or public
parks.
Refuse dumps can be eliminated either by transforming them into sanitary landfills or
by eradicating them altogether in an environmentally sound way, in which case they
should be replaced by a sanitary landfill elsewhere that will then receive the city’s
domestic waste. However such initiatives involve investment and operational costs
that in general are beyond municipalities’ financial means.
As a result of this situation the problem of solid waste disposal in Latin America is far
from being solved, as is revealed by PAHO reports on basic sanitary services (see chapter
1), according to which the percentage of cities that still have refuse dumps is very high.
One potentially positive economic factor being studied with increasing attention as a
solution to this problem is the exploitation of biogas naturally produced during organic
waste anaerobic decomposition processes, approximately 50% of which is methane.
This combustible gas can be used to fuel boilers, furnaces and vehicle internal
combustion engines or to generate electricity, with the additional advantage that its
producers will receive Certified Emission Reductions (CERs), as established in the Kyoto
Protocol the objective of which is to reduce the proportion of gases that provoke the
greenhouse effect in the earth’s atmosphere. The naturally occurring “greenhouse
effect” is a phenomenon of the Earth’s particular type of atmosphere that ensures
climatic conditions favourable for life as we know it.
This new opportunity is beginning to receive support from the World Bank and other
international development bodies, which are offering resources and information for
the installation of sanitary landfills with systems that recover and exploit “waste biogas”.
In this chapter we will try to clarify the question of carbon credits as the recovery and
use of biogas for fuel has already been dealt with in many technical publications.
13.9.1 Greenhouse effect: causes and consequences
This phenomenon is similar to the one produced by the glass panels of a greenhouse
that retain heat produced by the sun. As with the glass panels of a greenhouse, the
presence of certain gases in the atmosphere, principally water vapour, carbonic gas
and methane, impedes the release into space of heat generated by the incidence of
the sun’s rays on the Earth’s surface, which is then reflected outwards.
If this phenomenon did not exist, our planet would be as cold and sterile as Mars, for
example, while if it existed to a greater degree the Earth would be similar to Venus,
sterile and with an extremely high ambient temperature.
Over recent decades the concentration of these gases in the atmosphere has
increased, principally due to the intensive use of fossil fuels such as coal and oil in
domestic and industrial activities and in transport. Consequently, the average
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13. Solid waste final disposal
temperature on Earth is increasing, thus endangering the delicate balance that makes
our environment liveable.
A dramatic example of what a change in the Earth’s climate can imply is the extinction
of the dinosaurs that once lived all over the planet and, according to the most accepted
theory, disappeared when a layer of dust was raised by the impact of a meteorite on
the surface of the Earth provoking a drastic fall in global temperatures.
Out of a concern to stop, or at least reduce, the acceleration of this process the UN
called a summit, Rio 92, which established the “Framework Convention on Climate
Change” that finally became the Kyoto Protocol 6 signed in 1997 in the Japanese city of
that name.
The Kyoto Protocol established that between 2008 and 2012 countries listed in its
Annex 1 (developed countries) should reduce their emission of green-house gases
(GHG) to a level approximately 7 % below that of 1995.
Following its ratification by Russia in November 2004, the Kyoto Protocol came into
force on 16th February 2005, the moment at which the timeframe for commitments
taken on in that international agreement became applicable.
The Protocol defined a baseline criterion separating the group of surplus emission
producing countries (credit buyers) and the group of sub-baseline producing
countries (credit sellers). Consequently commitments were established that defined
greenhouse gas emission reduction goals for developed countries listed in Annex
1 of the Protocol and a program of reduction quota commercialization. Countries
not included in Annex 1 of the Protocol, such as Latin American and Caribbean
countries, are not obliged by the Protocol to reduce emissions but rather can
transfer to Annex 1 countries credits corresponding to emission reductions
produced by projects implemented for that purpose that qualify as what are called
CDM (Clean Development Mechanism) projects.
13.9.2 The “logic” of carbon credits
The interest in buying Certified Emission Reduction credits is due to differences
between countries in the cost of emission reduction through processes applied to
installations. In developed countries these costs can reach to values higher than US$
500.00 per ton of carbon while in countries not included in Annex 1 of the Protocol
they vary from US$ 1.00 to US$ 30.00 per ton of CO2.
As a result of these cost differences the Emissions Reduction Market was created
where the current value of a ton of CO2 or equivalent that is not emitted, or is captured,
is approximately US$ 10.00.
Global carbon markets have therefore begun to form and several international funds
have been created to support the development of projects that reduce anthropogenic
6.
Available on the Convention on Climate Change website http://unfccc.int/2860.php
249
carbon emissions. Each ton of CO2 that a developing country does not emit or captures
(that is, transforms for example into vegetable matter, a process called fixation in
plants) can be traded on the global market in the form of the above mentioned CER
credits.
In relation to the greenhouse effect it should be noted that each ton of methane is
equivalent to 21 tons of CO2. In consequence CERs are generated to the degree that
the combustion of methane takes place and the emission of CO2 equivalent is therefore
diminished.
For CERs to be issued, the planning, implementation and operation of a project should
be certified and audited by independent bodies authorized by the UN, taking into
account:
!
whether the project is entered into voluntarily, that is, it is not required by law;
!
whether there are real measurable long term benefits;
!
whether emission reductions are additional to those that would take place if the
project was not implemented (baseline).
The application of CDM to sanitary landfills is very effective for emission reduction,
requires low investment, is aligned with public policies for the improvement of sanitary
and environmental conditions and results in a better quality of life for the urban
population by contributing to the transformation of refuse dumps into sanitary landfills.
To take advantage of this new economic opportunity, Latin American cities are beginning
to invest in urban waste treatments that reduce methane emissions and generate income
through CERs linked to sanitary landfill projects implemented in accordance with CDM.
In Argentina for example, the concession for the collection and treatment of methane
produced by the large sanitary landfill at Villa Dominico, Buenos Aires, has been put to
tender with the support and assistance of the World Bank. This is the first Argentinean
project that has been presented to the Kyoto Protocol Executive Council as a CDM.
The first CDM project approved by the Executive Council is in Brazil: an electricity
generating station fuelled by methane from landfill biogas in Nova Iguaçu (Rio de Janeiro).
The project is expected to capture the equivalent of 2.5 million tons of carbonic gas
(US$ 4.5 per ton) and its first client is the government of the Netherlands.
Another Brazilian project for implementation in the Salvador Centre Metropolitan
sanitary landfill (Bahia), already approved by the Brazilian government through the Inter-
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13. Solid waste final disposal
ministerial Climate Commission, headed by the Science and Technology Ministry, is at
present awaiting the evaluation of the Kyoto Protocol Executive Council.
The first pilot project in Latin America was implemented in Uruguay at Las Rosas sanitary
landfill, Maldonando province, with the objective of capturing 18,962 tons of methane
over the course of 15 years.
It is therefore clear that the carbon credit market is rapidly expanding and adapting to
the CDM principles established by the Kyoto Protocol.
13.9.3 Circumstances in which biogas from
a sanitary landfill can be utilized
For an effective implementation of a biogas recovery and utilization project, with its
consequent reduction of methane emission into the atmosphere, there are requirements
that have to be met. Here we present some of the essential conditions that the various
sectors involved in the operation of an urban cleaning system should fulfil in order to
achieve the established objective.
Institutional
The mayor and secretaries of departments related to municipal solid waste management
and the environment should clearly and unequivocally demonstrate their intention to
implement a permanent program of domestic waste collection and final disposal that
covers the entire urban population (universal coverage) in order to ensure healthy
conditions for everybody and the protection of the local environment.
To achieve these objectives there must be a separate management unit within the
municipal administration with sufficient training to carry out these functions, as well as
a specific annual budget allocation to municipal solid waste management large enough
to cover the system’s investment and operational costs. There should also be a national
policy for solid waste management establishing minimum service provision standards
and requiring the implementation of final waste disposal systems that are both sanitarily
and environmentally sound.
Finally, an organizational agreement should be established between the different
institutions involved in the project such as the municipality; the company operating
the sanitary landfill where that service is subcontracted; the electricity distribution
company or gas consumer company where there is energy or gas generation using
biogas; and national, provincial or municipal environmental conservation bodies.
251
Physical and operational
The existence of a sanitary landfill principally dealing with the disposal of domestic
waste with a high organic matter content that has already received a minimum quantity
of 15,000 tons of waste (corresponding to 25,200 cubic metres, considering a density
of 0.7t/m³, which occupies a volume that can be represented, to give an idea, by a
10m high prism with sides of 60m); the layer of waste is at least 10 metres deep; the
surface of the landfill and its slopes are covered with clay except for the work face
where trucks unload; and there is a regular reception of at least 50 tons of domestic
waste per day.
If the site is not operated in a sanitary way, that is, the waste is not covered with clay
and there is no leachate and biogas collection, the possibility of recuperating the land
at the same time as sanitary or controlled operations begin on it should be examined.
Disposal operations should preferably continue on the site of the old refuse dump,
provided that the ownership, urban zoning and minimum environmental conditions are
appropriate, in order to avoid the difficulties involved in the implementation of a new
landfill in an urban area even when it will be operated on a sound basis.
Social
A public awareness raising program should be instigated focusing on the issue of urban
cleaning with a view to informing all citizens about sanitary problems in their region,
the resources needed to solve them and the responsibilities that each party has in the
process.
13.9.4 Requirements for the implementation of GHG
emission reduction projects in solid waste landfills
The implementation of emission reduction programs for methane produced in urban
waste landfills should comply with CDM requirements, so that they can be analyzed
and given different degrees of priority by the Interministerial Commission on Global
Climate Change, with a view to the possible allocation of public resources or investment
by the private sector at a national or international level.
In addition guarantees are required not only for an effective collection of the biogas
and the transformation of its methane into carbon dioxide (CO2) but also for the long
term continuity of the process as biogas continues to be produced during a period of
more than 15 years after the closure of a landfill as a waste disposal site.
Consequently the formulation of a table of conditioning factors is recommended that
can be filled in according to the specific characteristics of each project and subsequently
analyzed to determine if a given project can receive preliminary approval from the
national body responsible for the environment and later, where relevant, by the national
body responsible for climate change issues.
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13. Solid waste final disposal
The following is a list of project related characteristics that will facilitate the analysis
of a given project prior to a decision on whether or not basic CDM requirements are
met:
!
an urban population of more than 30,000 inhabitants;
!
the existence of a body responsible for urban cleaning in the municipality;
!
a qualified technical team within the responsible body;
!
a waste collection system coverage of at least 80% of the population;
!
a daily waste collection delivered to the site of at least 50 tons;
!
a landfill operation that is ongoing and functions in a regulated way: a sufficiency of
machines, a landfill growth plan that is followed, the compaction of waste and its
regular coverage with a layer of clay, more than 10 metre thick layers of waste, a
collection and either treatment or recirculation of leachate;
!
a sub-contraction of the landfill operation;
!
a municipal budgetary allocation specifically for urban cleaning services that is big
enough to maintain the quality of those services at an appropriate level;
!
a municipal urban cleaning or waste collection rate that covers more than 40% of
service costs;
!
an effective body of municipal regulations applicable to urban cleaning that may be
part of a general body of municipal regulations;
!
a political decision on the part of the mayor to recuperate the existing refuse dump,
where applicable, and install a new sanitary landfill;
!
the existence of land owned by the municipality that meets the environmental
conditions necessary for installing a sanitary landfill;
!
an existing or planned public awareness raising campaign on environmental issues
in general or urban cleaning in particular;
!
no depositing of industrial waste in the landfill.
13.9.5 General considerations
The relation between sanitary landfills and carbon credits is based in the fact that
landfill biogas capture and utilization projects, involving burning and transformation
into CO2, are less onerous than other GHG emission reduction options. Such sanitary
landfill projects are therefore likely to be of interest to large international corporations
as a way of obtaining cheaper CERs.
Even though income from CERs is not received immediately after the transformation
of a refuse dump into a sanitary landfill, in the medium term it can represent real financial
assistance for municipalities enabling them to ensure the correct operation of urban
253
solid waste final disposal installations. This offers municipalities a definitive and low
cost way of fulfilling their constitutional and moral duty to appropriately dispose of
waste produced in urban concentrations and provide basic sanitary conditions for the
inhabitants of the city they administer.
Finally it should be noted that the Intergovernmental Panel on Climate Change has
recently approved a new methodology for calculating the emissions avoided by
composting processes. This is of interest as it can facilitate the viability of projects
that add this form of waste treatment to the operation of sanitary landfills thus
extending their useful life, reducing leachate generation and avoiding methane emissions,
which can lead to CER income.
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BIBLIOGRAPHY
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS – ABNT. NBR 8.418; NB 842 – Apresentação
de projetos de aterros de resíduos industriais perigosos.
____________. NBR 1.057; NB 1.025 – Aterros de resíduos perigosos – Critérios para projeto,
construção e operação.
____________. NBR 10.004 – Classifica resíduos sólidos quanto aos seus riscos potenciais
ao meio ambiente e à saúde ambiente e à saúde pública, para que estes resíduos possam
Ter manuseio e destinação adequados.
____________. NBR 13.896 – Fixa condições mínimas exigíveis para projeto, implantação e
operação de aterros de resíduos não perigosos, de forma a proteger adequadamente as
coleções hídricas superficiais e subterrâneas próximas, bem como os operadores destas
instalações e populações vizinhas.
____________. NBR 8.419; NB 843 – Apresentação de projetos de aterros sanitários de resíduos
sólidos urbanos.
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WEB PAGES
Associação Brasileira de Embalagens de PET – ABEPET (http//www.abepet.com.br)
Associação Brasileira da Indústria de Plástico – ABIPLAST (http://www.abiplast.org.br)
Associação Brasileira de Celulose e Papel – BRACELPA (http:// www.bracelpa.com.br)
Associação Brasileira de Materiais Plásticos – PLASTIVIDA (http:// www.abiquim.org.br)
Associação das Indústrias Automáticas de Vidro – ABIVIDRO (http://www.abividro.org.br)
Virtual Library of Sustainable Development and Environmental Health (http://
www.bvsde.ops-oms.org)
Pan American Center for Sanitary Engineering and Environmental Sciences (http://
www.cepis.ops-oms.org)
Compromisso Empresarial para a Reciclagem – CEMPRE (http://www.cempre.org.br)
Empresa Recicladora de Latas de Alumínio – LATASA (http://www.latasa.com.br)
Environmental Industry Associations - (http://www.envasns.org)
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GLOSSARY OF ACRONYMS
ABNT – Brazilian Institute of Technical Standards
ASCE – American Society of Civil Engineers
BOD – Biochemical Oxygen Demand
CEPIS/PAHO – Pan American Center for Sanitary Engineering
and Environmental Sciences
CER – Certified Emission Reduction
CDM – Clean Development Mechanism
CNEN – National Nuclear Energy Commission, Brazil
COD – Chemical Oxygen Demand
COMLURB – Rio de Janeiro Urban Cleaning Company
CONAMA – National Commission on the Environment, Brazil
EIS – Environmental Impact Study
EMS – Environmental Management Secretariat, IDRC
GHG – Green-House Gas
HDI – Human Development Index
HDPE – High Density Polyethylene
IADB – Inter-American Development Bank
IBAM – Brazilian Institute of Municipal Administration
IDRC – International Development Research Centre of Canada
IPCC – Intergovernmental Panel on Climate Change
IPE – Individual Protection Equipment
ISWM – Integrated Solid Waste Management
ISWMP – Integrated Solid Waste Management Plan
LAC – Latin America and the Caribbean Region
LDPE – Low Density Polyethylene
MoU – Memorandum of Understanding
NGO – Non-Governmental Organization
PAHO – Pan-American Health Organization
PET – Polyethylene Terephtalate
PVC – Poly Vinyl Chloride
Rio 92 – United Nations International Conference on Environment
and Development (Rio de Janeiro, 1992)
SISNAMA –National Environmental System, Brazil
TGW –Total Gross Weight
UN – United Nations
VDC – Voluntary Drop-off Centres
WCR – Waste Collection Rate
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GLOSSARY
Biogas: combustible gas naturally generated during the organic matter putrefaction process.
Clean technology: technology that does not produce secondary effects or impact on the
environmental balance or natural systems.
Compensatory measures: measures to compensate communities or social groups for
the use of non-renewable environmental resources, or for unavoidable negative environmental
impacts.
Composting: procedures for the transformation of biodegradable organic municipal solid
waste into organic compounds.
Domestic waste: residential waste and waste from small commercial generators.
Environmental impact assessment: a procedure aimed at identifying and interpreting the
effects of public or private actions or projects that may cause environmental impacts or
alter the quality of life.
Final disposal: the final process applied to solid waste resulting in its ultimate placement.
Governing plan: a fundamental legally binding policy instrument for the development and
organization of the municipal territory aimed at guaranteeing an appropriate social functioning
of the city.
Greenhouse effect: the absorption by the Earth’s atmosphere of infrared radiation emitted
by its surface, resulting in increased heat on the Earth’s surface and thus an increase in the
average temperature of the planet. This phenomenon stops heat from the sun leaving the
atmosphere and returning to space, replicating on a planetary scale an effect similar to the
one observable in a greenhouse.
Healthcare institutions: public and private hospitals, laboratories, clinics, veterinary clinics,
medical centres and all other establishments where any level of human or animal healthcare
is practiced with a view to prevention, diagnosis, treatment or rehabilitation.
Indivisible service: a public service available to all tax-payers that cannot be measured
on the basis of the amount used by individual citizens.
Integrated solid waste management plan: a technical planning instrument for activities
linked to urban cleaning.
Intermediary agents: agents involved in the commercialization of recyclable materials in
general as intermediaries in sales by segregators to recycling companies, which implies a
reduced financial income for segregators.
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Leachate: liquid that drains through solid waste, contains materials in solution or in
suspension and results from the decomposition process plus the infiltration of rainwater.
Master plan: a document containing all of the necessary elements for the complete
implementation of a project in accordance with relevant technical regulations.
Medical waste: all waste generated by healthcare institutions.
Municipal Treasury: the resources of a municipality out of which the municipal budget is
financed.
Municipal waste: solid or semisolid waste generated by activities in population centres, of
residential, commercial or institutional origin, or from markets, healthcare institutions, small
industries and the sweeping and cleaning of public spaces.
Organic law: a municipality’s foundational law defining the areas of jurisdiction and
responsibility for its executive, legislative and judicial branches.
Plant: a solid waste processing site including the land, structures, works and added features.
Recycling company: a company specializing in the recycling of material.
Refuse: all waste produced by human activity that is not reused.
Refuse dump: a place where waste is indiscriminately dumped in the open air without the
application of any sanitary treatment.
Segregator: a person engaged in the separation of recyclable material from refuse, also
called scavenger or waste picker.
Solid waste management: all technical and administrative activity, including planning, design
and evaluation, that is related to appropriate solid waste management.
Urban cleaning service: all activities relating to solid waste management: preparation
and storage, collection, transport, transfer, street cleaning, recyclable material recovery,
treatment and final disposal of solid waste.
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