Water Quality Improvement Through Proper Design and Construction of
Wastewater Collection Systems in Dar-es-Salaam, Tanzania
By Tula Ngasala
WATER QUALITY TEST
EXISTING CONDITION
In urban areas of Dar-es-Salaam, Tanzania, water scarcity and wastewater
Common Sanitation Practices
management are two of the greatest challenges communities face as a
result of because very high population, close proximity of houses to each Only 8% of the households from this community have access to Figures 4 and 5 below show two types of wastewater
other, and failure of the sanitation facilities to comply with proper design sewerage system, the rest are contributing to improper disposal of collection systems commonly used. These latrines function
wastewater. The highest percentage use pit latrines and septic tanks as both a toilet and shower/bathroom. The combined
specifications to minimize contamination.
which are not designed and constructed to meet the minimum collection of wastewater (wash water and feces) results in the
requirement to function properly.
rapid filling of the storage pits that are often allowed to
8%
overflow on streets, especially during rainy season.
1% (Open
(Connected
defecation)
to sewerage
System)
24% (Septic
Tanks)
The figures below show the results of the analysis of
drinking water samples. As noted, most samples contain
these analytes at concentrations greater than the
minimum standards for drinking water. The presence of
nitrate indicates the possibility of fecal contamination.
180
Nitrate Content in Drinking Water
160
140
Concentration (mg/l)
INTRODUCTION
Well Water
120
Collected Rainwater
100
80
60
40
55% (Pit
Latrines)
U.S EPA & WHO
Standard
10mg/L
20
0
B1
B2
B3
B4
B5
C2
C1
Drinking Water Sources
Study Area
12%
(Ventilated
Pit Latrines)
Figure 4: Pour flush toilet with 2-chamber
septic Tank and soak pit
Figure 5: Offset single pit toilet
with pour flush
1600
1400
Figure 3: Distribution of Sanitary Technologies in Dar-es-Salaam
Concentration (mg/l)
Surface and Groundwater Contamination
STUDY AREA
•
•
•
•
A
Figure 9: Rain Water
Collection System
Figure 8: Pumping
well
Due to the scarcity of water in the area, the local community has few
options but to drink poor quality surface and ground water. Most of the
drinking water is likely contaminated with sewage due to poor design
and construction of sanitation facilities and wells.
C1
B1
Figure 10: Vendor selling water obtained from unknown sources
Distribution of Monthly Expenditures
Community members from this area spend approximately 68% of
their income to purchase water and pay for emptying their pit latrines
and septic tanks.
Wastewater
B2
Other
Expenses
32%
C2
B3
Domestic
Water Use
65%
Legend:
- Sampling sites
Figure 2: Mabibo Area in Dar-es-Salaam: (1) Red circles show drinking water sampling locations,
(2) Locations A, B and C are University Dormitories, Industrial Processing Zone and Vegetable
Farm Land respectively.
200
B2
B3
B4
B5
C2
C1
C3
• In Summer 2015, extensive sampling of water for
domestic use from all three sources in Study Area.
• Additional surveys with the goal of determining the
extent of contamination, potential
sources of
contamination, and associated health risks.
• Estimation of the wastewater loading coming from
upstream, which contributes to the contamination of
the river in the Study Area.
LONG TERM OBJECTIVES
Management
3%
B4
400
NEXT STEP…
C
C3
U.S EPA &WHO
Standard 500mg/L
600
Drinking Water Sources
Drinking Water Contamination
Vegetable
Farm Land
800
B1
Figure 7: River contaminated by
sewage
B
Collected Rainwater
1000
0
Figure 6: Sewage overflow from an outfall
structure
Industrial
Processing
Zone
B5
Water Scarcity
The insufficient treatment and improper disposal of wastewater is very Three main sources of water for domestic use in this area are from
common, which results in contamination of nearby waterbodies private wells (70-80 m deep), rain water collected and stored in
surface or underground tanks, and from vendors (See Figures 8, 9
including rivers, lakes, and beaches.
and 10).Community get City Water only once or twice a month.
The study area is the small part of urban area in Dar-es-Salaam, with a
population of approximately 5000 people.
The community members have a very low income and spend nearly 70% of
their income paying for domestic water and wastewater management.
Untreated sewerage is commonly discharged into the river or released onto
the ground surface, especially during rainy seasons, when the wastewater
is intentionally mixed with runoff.
Other major contributions to the surface water contamination are
wastewater coming from university dormitories and industrial wastes from
Industrial Processing Zone (see Figure 2). The contaminated water from the
river is used to irrigate food crops, which are sold to the local community.
University
Dormitories
Well Water
1200
CHALLENGES
Figure 1: Study area location located on the eastern part of Tanzania
Total Dissolved Solids Content in Drinking Water
• Modeling of low-cost decentralized wastewater
treatment system to predict the resulting
improvements in surface water and drinking water
quality.
• Sources, Fate, and Transport of Nitrate and other
contaminants in the study area
REFERENCES
1. Introduction to Environmental Sanitation. 2015. Available at:
http://www.slideshare.net/ZakiUddinAhmad/introduction-toenvironmental-sanitation. Accessed March 1, 2015.
2. WHO. Guidelines for drinking-water quality, volume 3: Drinking-water
quality control in small-community supplies, WHO, Geneva, 1985.
ACKNOWLEDGEMENTS
•
•
Figure 12: Groundwater Pollution from Pit Latrines
(Dahi, 1996)
Figure 11: Monthly income expenditure
Special thanks to my advisors: Drs. Susan Masten and
Phanikumar Mantha for their guidance
The Department Chair, Dr. Neeraj Buch for his financial
support