1. business and industrial
2. chemicals industry
3. dyes and pigments

Journal of Chemistry and Chemical Sciences, Vol. 5(4), 153-168, April 2015
(An International Research Journal), www.chemistry-journal.org
ISSN 2229-760X (Print)
ISSN 2319-7625 (Online)
Analysis of Copper, Chromium & Lead in Hawassa and
Arba Minch Textile Effluents
Tessema Bashaye Tafesse and Adane Kassa Yetemegne
Department of Chemistry,
Arba Minch University, ETHIOPIA.
e-mail: [email protected].
(Received on: April 23, 2015)
ABSTRACT
Waste water generated from the textile processing industries contains high
amounts of dissolved solids, heavy metals and other auxiliary chemicals that are
used in the various stages of dyeing and other processes. Therefore analysis of trace
meals in wastewater is prerequisite for the investigation of the degree of pollution
and appropriateness of treatment plant. In this study the Trace Metals: Copper (Cu),
Chromium (Cr), and Lead (Pb) in textile effluents and adjacent water samples were
assessed.
Wastewater sample in triplicates from Hawassa and Arba Minch textile
effluents & adjacent water bodies (Chamo Lake, Hawassa Lake and Tikur Woha)
were collected. The collected samples were digested using HNO3 and the
concentrations of the metals were determined using Flame Atomic Absorption
Spectrophotometer. The analytical results obtained were compared with standard
values for wastewater set by authorized bodies. The result showed that concentration
heavy metals in samples ranges from 0.143-1.000, 0.517-0.986 and 1.350-4.350
mg/L for copper, chromium and lead respectively In Hawassa textile effluents and
neighboring water bodies. In Arba Minch textile effluents and neighboring water
bodies it was ranged from 0.143-1.000, 0.244-0.350 and 0.050-1.200 mg/L for
copper, chromium and lead respectively. All samples exceeded the prescribed
guideline limit in effluents of textile and associated water bodies. The findings also
indicate that the Cr contamination was more than other metals. Effluents of Hawassa
textile showed larger concentration of heavy metals which indicate high degree of
pollution. This textile effluent may be source of water pollution which will affect the
flora and fauna existing in such environments hence textile effluent must be treated
before they are discharged into the environment.
Keywords: Heavy metal, Pollution, Textile Industry Effluent, Trace metals.
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1. INTRODUCTION
Textile processing operations are considered an important part of the industrial
sector in both developed and developing countries, like Ethiopia. However the textile
industry is one of the most complex manufacturing industries with operations and processes
as diverse as its products. Due to this diversity it is almost impossible to describe a “typical”
textile effluent1. The technology of transforming cotton and synthetic fibers into fabrics and
dyed fabrics generates various kinds of wastes. However, environmental problems of the
textile industries are mainly caused by discharges of wastewater/effluents during dyeing and
finishing processes2. The textile wet finishing processes considered were denim wet
processing, garment wash and fabric dyeing. The major processing steps on the wet
processing of denim garments involve desizing, stone-washing, bleaching and neutralization
and fabric softening. Desizing involves the removal of starch based sizes added during fiber
processing by treating the denim with commercial amylase enzymes. Stone washing is a
more severe form of cellulous treatment which is essentially a degradative mechanism
resulting in the loss of both the weight and strength of the fabric giving the material a worn
out appearance. Bleaching and neutralization is normally conducted to remove unwanted
color in preparation for dyeing3.
Fabric dyeing involves the following major steps; scouring, bleaching, dyeing, dye
fixation and fabric softening. Scouring is performed to remove impurities through the use of
alkaline baths prior to further wet processing. Garment washing involves the use of
detergents and softeners to remove dirt and improve the fabric texture before finished
garments are sent to the market3.
All the three textile finishing processes are water-intensive requiring large volumes
of water for processing and rinsing. Furthermore, a wide variety of chemicals, detergents and
softeners are also employed to improve the efficiency of each process. Since the processing
and rinsing steps are conducted as batch operations and there are stringent water quality
requirements for each processing step, water used is normally used once for each processing
step or rinse before being discharged. This greatly increases the discharge volume and fresh
water requirements for the wet processes. Thus, it is important to fully characterize the
effluent from the major industrial dischargers in order to analyze the pollutant load before
and after treatment and to enable recommendations for other treatment requirements2-5. The
wastewater generated from the textile processing industries contains high amounts of
suspended solids, dissolved solids, unreacted dyestuffs (color), BOD, COD, heavy metals
and other auxiliary chemicals that are used in the various stages of dyeing and other
processes4-9.
Textile wastewater contains substantial pollution loads in terms of heavy metals and
other toxic chemicals. The concentration of these trace metal in effluents must be treated and
reduced to permissible level before disposed in to the environment. However the treatment
process commonly used in textile industries will not be efficient and very little work has
been done on the characterization of textile wastewater in Ethiopia in general and southern
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Ethiopia particularly. The study will help to assess whether the effluents discharged by this
two factories are in accordance with the guide line that is set for industrial wastewater by
EPA in Ethiopia and other international standards. It will also serve policy makers to design
a preventive measure to the health and environmental problems due to industrial pollution.
There was no sufficient published and accessible data on the characterization of effluents of
textile industry in Ethiopia. Therefore the finding will be used as a base line data for further
investigation. It will also be a new study area for researchers to focus on the effluent
chemical toxicity on the public health and environmental pollution in Ethiopia. Treatment
plant for a certain textile industry is designed based on the type and amount of effluent
produced at the end of the production. Therefore the finding of this study will be used to the
investigation of treatment options so as to release waste water which is safe to the
environment.
Source of Heavy Metals
The source of heavy metals in dyes is from premetallized dyes (3% to 4% metal);
basic dyes requiring preparation as a double salt of zinc; dichromates to oxidize and fix dyes;
and chromium compounds from after chroming operations in wool dyeing (Table 2.1 shows
the content of heavy metals in dyes).
There are mainly two sources of metals. Firstly, the metals may come as impurity
with the chemicals used during processing such as caustic soda, sodium carbonate and salts.
Secondary, the source of metal could be dye stuffs like metalized mordent dyes10.
Table 2.1 Heavy Metal Content of Dyes
Metal
Arsenic
Cadmium
Chromium
Cobalt
Copper
Lead
Mercury
Zinc
Typical Conc. (ppm)
<1-4.4
<1
-3-83
<1-3.2
33-110
6-52
0.5-1
3-32
Dye Type With Highest Metal Content
Reactive
All types
Vat
Acid
Vat
Reactive
Vat
Basic
Metal complex dyes contain chelated chromium, cobalt, copper and nickel. Some
cationic dyes contain zinc and trace concentrations of mercury, cadmium and arsenic can be
present as impurities from intermediates. Some oxidizing and reducing agents contain metals
(e.g. dichromate and permanganate), but in most cases, these chemicals are no longer in use.
Metals are also present in finishes such as antifungal and odor-preventive finishes, water
repellents and flame retardants11.
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2.6 Effects of Heavy Metals on Human Health
The heavy metals hazardous to humans include lead, mercury, cadmium, arsenic,
copper, zinc, and chromium. Such metals are found naturally in the soil in trace amounts,
which pose few problems. Arsenic and cadmium, for instance, can cause cancer. Mercury
can cause mutations and genetic damage, while copper, lead, and mercury can cause brain
and bone damage.
Copper
Copper, like lead, can enter water by dissolution of the corrosion product, basic
copper carbonate. The solubility is mainly a function of pH and total inorganic carbon.
Solubility decreases with increase in pH, but increases with increase in concentrations of
carbonate species.
The pitting of copper is commonly associated with hard ground waters having a
carbon dioxide concentration above 5mg/L and high dissolved oxygen. Surface waters with
organic color may also be associated with pitting corrosion. Copper pipes can fail by pitting
corrosion, which involves highly localized attacks leading to perforations with negligible loss
of metal.
Copper is both an essential nutrient and a drinking-water contaminant. It has many
commercial uses. It is used to make pipes, valves and fittings and is present in alloys and
coatings.
Copper concentrations in treated water often increase during distribution, especially
in systems with an acid pH or high-carbonate waters with an alkaline pH. Food and water are
the primary sources of copper exposure in developed countries. Consumption of standing or
partially flushed water from a distribution system that includes copper pipes or fittings can
considerably increase total daily copper exposure, especially for infants fed formula
reconstituted with tap water.
IPCS concluded that the upper limit of the acceptable range of oral intake in adults is
uncertain but is most likely in the range of several (more than 2 or 3) but not many
milligrams per day in adults12. This evaluation was based solely on studies of gastrointestinal
effects of copper-contaminated drinking-water. The available data on toxicity in animals
were not considered helpful in establishing the upper limit of the acceptable range of oral
intake due to uncertainty about an appropriate model for humans, but they help to establish a
mode of action for the response. Recent studies have delineated the threshold for the effects
of copper in drinking-water on the gastrointestinal tract, but there is still some uncertainty
regarding the long-term effects of copper on sensitive populations, such as carriers of the
gene for Wilson disease and other metabolic disorders of copper homeostasis.
The 1958 WHO International Standards for Drinking-water suggested that
concentrations of copper greater than 1.5 mg/liter would markedly impair the potability of
the water. The 1963 and 1971 International Standards retained this value as a maximum
allowable or permissible concentration. In the first edition of the Guidelines for DrinkingApril, 2015 | Journal of Chemistry and Chemical Sciences | www.chemistry-journal.org
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water Quality, published in 1984, a guideline value of 1.0 mg/liter was established for
copper, based on its laundry and other staining properties. This guideline value was retained
in the addendum to the Guidelines published in 1998 and remained provisional as a result of
uncertainties in the dose–response relationship between copper in drinking-water and acute
gastrointestinal effects in humans. It was stressed that the outcome of epidemiological
studies in progress in Chile, Sweden and the USA may permit more accurate quantification
of effect levels for copper-induced toxicity in humans, including sensitive subpopulations.
2.6.2 Chromium
Effects in humans occupationally exposed to high levels of chromium or its
compounds, primarily Cr(VI) by inhalation, may include irritating respiratory effects,
possible circulatory effects, effects on stomach and blood , liver and kidney effects, and
increased risk of death from lung cancer13. Evidence from studies on experimental animals
shows that Cr(VI), especially those of low solubility, can induce lung cancer. Trivalent
chromium is not considered to be carcinogenic. There is, according to the IPCS monograph,
insufficient evidence to implicate chromium as a causative agent of cancer in any organ other
than the lung. The exposure circumstance entails exposures that are carcinogenic to
humans14. Exposure to Cr(VI) and Cr(III) compounds can be associated with allergic
responses (e.g., asthma and dermatitis) in sensitized individuals. People who work with
material containing mere traces of chromium salts are more at risk than workers who
occasionally come into contact with high concentrations of chromium salts.
Adverse effects of the hexavalent form on the skin may include ulcerations,
dermatitis, and allergic skin reactions. Inhalation of hexavalent chromium compounds can
result in ulceration and perforation of the mucous membranes of the nasal septum, irritation
of the pharynx and larynx, asthmatic bronchitis, bronchospasms and edema. Respiratory
symptoms may include coughing and wheezing, shortness of breath, and nasal itch.
According to National Toxicology Program (NTP), there is sufficient evidence for
carcinogenicity in experimental animals for the following hexavalent chromium compounds;
calcium chromate, chromium trioxide, lead chromate, strontium chromate, and zinc
chromate.
2.6.3 Lead
Lead in the environment is mainly particulate bound with relatively low mobility and
bioavailability. Lead does, in general, not bioaccumulate and there is no increase in
concentration of the metal in food chains. Lead is not essential for plant or animal life50. For
infants and young children lead in dust and soil often constitutes a major exposure pathway
and this exposure has been one of the main concerns as to the exposure of the general
population. The intake of lead will be influenced by the age and behavioral characteristics of
the child and the bioavailability of lead in the source material. Baseline estimates of potential
exposure of children to dusts, including intake due to normal hand-to-mouth activity, are
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0.2 g/day for children 1.6 years old when both indoor and outdoor ingestion of soil and dust
is considered, but for some children it may be up to 5 g/day15 of particular concern for the
general population is the effect of lead on the central nervous system. Epidemiological
studies suggest that low level exposure of the fetus and developing child may lead to
reprotoxic effects, i.e. damage to the learning capacity and the neuropsychological
development16. Studies of children indicate a correlation between higher lead contents in the
blood and a lower IQ. Some of the effects are reversible, whereas chronic exposure to high
lead levels may result in continued decreased kidney function and possible renal failure.
Renal effects have been seen among the general population when more sensitive indicators
of function were measured. The reproductive effects of lead in the male are limited to sperm
morphology and count. In the female, some adverse pregnancy outcomes have been
attributed to lead. Lead does not appear to have deleterious effects on skin, muscle or the
immune system. The agent (mixture) is possibly carcinogenic to humans. The exposure
circumstance entails exposures that are possibly carcinogenic to humans.
2.7 Effects of Heavy Metals on Aquatic Organisms
Dyes may affect the photosynthetic activity in aquatic life due to reduced light
penetration and may also be toxic to some aquatic life due to the presence of aromatics,
metals, etc. in them17-18 aquatic organisms are adversely affected by heavy metals in the
environment. The toxicity is largely a function of the water chemistry and sediment
composition in the surface water system19. The metals are mineralized by microorganisms,
which in turn are taken up by plankton and further by the aquatic organisms. Finally, the
metals by now, several times biomagnified is taken up by man when human consume fish
from the contaminated water.
Slightly elevated metal levels in natural waters may cause the following sublethal
effects in aquatic organisms:
i.) histological or morphological change in tissues;
ii.) Changes in physiology, such as suppression of growth and development, poor swimming
performance, changes in circulation;
iii.) Change in biochemistry, such as enzyme activity and blood chemistry;
iv.) Change in behavior; and
v.) Changes in reproduction20.
Many organisms are able to regulate the metal concentrations in their tissues. Fish
and crustacea can excrete essential metals, such as copper, zinc, and iron that are present in
excess. Some can also excrete non-essential metals, such as mercury and cadmium, although
this is usually met with less success20.
Research has shown that aquatic plants and bivalves are not able to successfully
regulate metal uptake20. Thus, bivalves tend to suffer from metal accumulation in polluted
environments. In estuarine systems, bivalves often serve as biomonitor organisms in areas of
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suspected pollution21. Shellfishing waters are closed if metal levels make shellfish unfit for
human consumption.
In comparison to freshwater fish and invertebrates, aquatic plants are equally or less
sensitive to cadmium, copper, lead, mercury, nickel, and zinc. Thus, the water resource
should be managed for the protection of fish and invertebrates, in order to ensure aquatic
plant survivability22. Phytoplankton and zooplankton often assimilate available metals
quickly because of their high surface area to volume ratio. The ability of fish and
invertebrates to adsorb metals is largely dependent on the physical and chemical
characteristics of the metal21. Metals may enter the systems of aquatic organisms via three
main pathways:
i.) Free metal ions that are absorbed through respiratory surface (e.g., gills) are readily
diffused into the blood stream.
ii.) Free metal ions that are adsorbed onto body surfaces are passively diffused into the
blood stream.
iii.) Metals that are adsorbed onto food and particulates may be ingested, as well as free ions
ingested with water20. For eg: Chromium is not known to accumulate in the bodies of
fish, but high concentrations of chromium, due to the disposal of metal products in
surface waters, can damage the gills of fish that swim near the point of disposal.
METHODS AND MATERIALS
Sampling Area
Samples were collected from Hawassa Textile effluents, Tikur Wuha, Hawassa
Lake, Arba Minch Textile effluents and Chamo Lake.
Sample Collection and Preparation
Wastewater samples was collected in plastic containers previously cleaned by
washing in non-ionic detergent, rinsed with tap water and later soaked in 10% HNO3 for 24
hours and finally rinsed with deionized water prior to usage. During sampling, sample bottles
were rinsed with water which was sampled. Wastewater was collected before treatment, after
treatment at lagoon, and from Tikur Wuha River, Hawassa Lake and Chamo Lake at the peak
hour of production in one month interval in triplicate. All the samples collected were
analyzed separately. Then the samples were stored in the refrigerator at about 4oc prior to
analysis.
The samples were digested using HNO3 as follows. The sample, 100ml is transferred
into a beaker and 5ml concentrated HNO3 is added. The beaker with the content then is
placed on a hot plate and evaporated down to about 20ml; after it cools another 5ml
concentrated HNO3 is also added. Then the beaker is covered with watch glass and is
returned to the hot plate. The heating is continued and then small portion of HNO3 is added
until the solution appeared light colored and clear. The beaker wall and watch glass is
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washed with distilled water and then filtered to remove any insoluble materials that could
clog the atomizer. Finally the volume is adjusted to 100ml with deionized water.
Determination of Concentration of Heavy metals
Atomic Absorption Spectrophotometer was calibrated for each element using
standard solution of known concentration before sample injection23. Blank solutions,
standard, and Sample were pipetted and loaded on the AAS according to the following
sequence: blank, lowest to highest standard, then sample and absorbance readings were done.
Metals concentrations such as, Copper (Cu), Chromium (Cr) and Lead (Pb) samples were
analyzed on Atomic Absorption Spectrophotometer by using specific cathode lamp in Arba
Minch University chemistry laboratories, Arba Minch. The calibration curve, obtained from
the absorbance data of standard solutions with varying concentrations was used to calculate
the mg/L concentration of metals in waste effluent and neighboring water.
Data Analysis
The obtained data was analyzed by descriptive statistics (Minimum conc., Maximum
Conc., Mean conc. and standard deviation by using SPSS (Statistical Package for Social
Sciences)). The all figures were generated by Microsoft Office Excel 2007 during the
analysis of EIA process and were used directly for results interpretation. The precision of the
all analyses were measured using the standard deviation techniques and calculated in mg/L
for the each sample.
Reagents and Glass Wares
All the chemicals used were analytical grade, chemicals and Atomic Absorption
spectroscopic standard solutions of metals were used for metal analysis. De-ionized water
was used for sample and standard solution dilution or preparation. Borosilicate glass wares
(conical flask, volumetric flask, watch glass, pipette, measuring cylinder, etc.) were used for
the preparation of blank, sample and standard solutions. Polyethylene bottles were used for
sample collection.
3. RESULT AND DISCUSSION
A number of azo dyes were used in textile printing industries24. Waste water was
being discharged directly into drains that connect the industry to the main drainage network
to The River Tikur Wuha which flows in Hawassa Lake in the city.
Heavy Metals Analysis
Among various industries, textile industries are major producer of metals like
chromium, iron, manganese, copper, lead, cadmium and nickel etc. All the collected samples
were analyzed for copper, chromium, and lead and they were detected in each sample.
The absorbance of standard solution for determination of concentration of heavy
metals of interest were given below in Table 3.2.
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Table 3. 1 Absorbance Data for the Calibration Standards
Concentration (mg/L)
2
4
6
8
2
4
6
8
2
4
6
8
Copper Standard
Absorbance
Absorbance Mean
0.040
0.040
0.04
0.040
0.045
0.044
0.044
0.043
0.066
0.068
0.067
0.067
0.083
0.087
0.085
0.085
Chromium Standards
0.010
0.013
0.011
0.080
0.082
0.080
0.200
0.240
0.210
0.405
0.401
0.413
Lead Standards
0.081
0.090
0.077
0.148
0.144
0.150
0.161
0.166
0.175
0.209
0.232
0.200
Standard Deviation
0.000
0.001
0.001
0.002
0.011
0.001
0.081
0.001
0.217
0.017
0.406
0.005
0.083
0.005
0.147
0.002
0.167
0.006
0.214
0.013
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The calibration curve for standard solution obtained to examine the status of metals
in textile effluents and their contamination associated with neighboring water bodies (Fig 3.9
- Fig.3.11) and data analysis were given in Table 3.3 below.
Fig. 3. 1 Calibration Curve for the Determination of Copper in Hawassa and Arba Minch Textile Waste
and Neighboring Water.
Fig. 3. 2 Calibration Curve for the Determination of Chromium in Hawassa and Arba Minch
Textile Waste and Neighboring Water.
Fig. 3. 3 Calibration Curve for the Determination of Lead in Hawassa and Arba Minch Textile Waste and
Neighboring Water.
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Table 3. 2 Absorbance Data and Calculated Concentration of Heavy Metals in Hawassa Textile
Waste Water and Neighboring Water Bodies.
Copper
Sample sites
Textile
Waste
Before Treatment
Textile Waste After
Treatment
Tikur Wuha
Hawasa Lake
Absorbance
Calculated
Conc.
0.021
0.286
0.020
0.143
0.021
0.022
0.022
0.023
0.024
0.020
0.023
0.026
0.025
0.027
0.286
0.429
0.429
0.571
0.714
0.143
0.571
1.000
0.857
1.143
0.020
0.022
0.532
0.562
0.019
0.517
0.040
0.043
0.835
0.880
0.050
0.986
0.030
0.033
0.031
0.040
0.044
0.041
0.683
0.729
0.698
0.835
0.895
0.850
0.077
0.076
1.400
1.350
0.079
1.500
0.126
0.125
0.128
0.129
0.130
0.126
0.136
0.133
0.132
3.850
3.800
3.950
4.000
4.050
3.850
4.350
4.200
4.150
Mean
Conc.
Standard
Deviation
Maximum
Conc.
Minimum
Conc.
0.238
0.067
0.286
0.143
0.476
0.067
0.571
0.429
0.476
0.243
0.714
0.143
1.000
0.117
1.000
0.857
0.562
0.517
0.986
0.835
Guide Line
Limit
(mg/L)[25]
≤ 0.250
Chromium
Textile
Waste
Before Treatment
Textile Waste After
Treatment
Tikur Wuha
Hawasa Lake
0.537
0.019
0.900
0.063
≤ 0.100
0.703
0.860
0.019
0.026
0.729
0.895
0.683
0.835
Lead
Textile
Waste
Before Treatment
Textile Waste After
Treatment
Tikur Wuha River
Hawasa Lake
1.417
0.062
1.500
1.350
3.867
0.062
3.950
3.800
3.967
0.085
4.050
3.850
4.233
0.085
4.350
4.150
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≤ 0.100
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Table 3. 3 Absorbance Data and Calculated Concentration of Heavy Metals in Arba Minch
Textile Waste Water and Neighboring Water Bodies.
Sample sites
Textile
Waste
Before Treatment
Textile
Waste
After Treatment
Chamo Lake
Absorbance
Calculated
Conc.
0.020
0.021
0.022
0.024
0.023
0.021
0.026
0.025
0.025
0.143
0.286
0.429
0.714
0.571
0.286
1.000
0.857
0.857
0.001
0.003
0.002
0.002
0.004
0.003
0.005
0.007
0.008
0.244
0.274
0.259
0.259
0.289
0.274
0.305
0.335
0.350
0.050
0.051
0.052
0.053
0.051
0.051
0.060
0.070
0.073
0.050
0.100
0.150
0.200
0.100
0.100
0.550
1.050
1.200
Copper
Mean
Conc.
Standard
Deviation
Maximum
Conc.
Minimum
Conc.
0.286
0.117
0.429
0.143
0.524
0.178
0.714
0.286
0.905
0.067
1.000
0.857
0.259
0.012
0.259
0.244
0.274
0.012
0.289
0.259
0.33
0.019
0.350
0.305
0.100
0.041
0.150
0.050
0.133
0.047
0.200
0.100
0.933
0.278
1.200
Guide
Line Limit
(mg/L)[25]
≤ 0.250
Chromium
Textile
Waste
Before Treatment
Textile
Waste
After Treatment
Chamo Lake
≤ 0.100
Lead
Textile
Waste
Before Treatment
Textile
Waste
After Treatment
Chamo Lake
≤ 0.100
0.550
Graphs of Comparison of Sample Concentration with Guideline Limit.
Fig. 3. 4 Comparison of Concentrations of Copper with Guide Line Limit in Hawassa Textile Industry
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Fig. 3. 5 Comparison of Concentrations of Chromium with Guide Line Limit in Hawassa Textile Industry
Fig. 3. 6 Comparison of Concentrations of Lead with Guide Line Limit in Hawassa Textile Industry
The data of metal concentration in textile effluents are furnished in Table 3.3 & 3.4.
Analytical results revealed that the concentration of chromium in effluents of textile
industries were recorded maximum of 0.986 and minimum of 0.517mg/L, in Hawassa (Table
3.3); maximum of 0.350 and minimum of 0.244mg/L in Arba Minch textile industries (Table
3.4). In all cases the concentrations of Chromium is above the guideline limit (≤ 0.100mg/L).
This high concentration may cause allergic reactions in the skin, damage the lungs, and
asthma attacks26.
Concentration of copper was found maximum of 1.000 and minimum of 0.143 mg/L
for both Hawassa textile and Arba Minch textile industries. For most of the samples taken
the concentration of copper exceeds the guideline limit. Copper is an essential element in
mammalian nutrition as a component of metallo-enzymes in which it acts as an electron
donor or acceptor. Conversely, exposure to high levels of copper can result in a number of
adverse health effects.
Maximum value of lead was 4.350mg/L and minimum of 1.350 mg/L in textile
effluent of Hawassa (Table 3.3). On the other hand maximum of 1.200mg/L and minimum of
0.050mg/L of lead were noted in waste water samples of Arba Minch industry (Table 3.4).
The values for Arba Minch were 27.59% lower for maximum and 3.7% lower for minimum
as compared to the values of Hawassa textile and neighboring water bodies. Excess amount
of lead affects central nervous system, particularly in children and also damages kidneys and
the immune system.
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Generally the mean concentration before and after treatment of heavy metals such as
Cu, Cr, and Pb were 0.286±0.117; 0.259±0.012 and 0.100±0.041mg/L & 0.524±0.178;
0.274±0.012; and 0.133±0.047mg/L respectively for metals of Arba Minch and 0.238±0.067;
0.537±0.019 and 1.417±0.062mg/L & 0.476± 0.067; 0.900±0.063 and 3.867± 0.062 mg/L
respectively for heavy metals of Hawassa textile effluent. Calculated standard deviation
values related to the distribution of these metals before treatment and after treatment show a
very close dispersion around the mean (the data are more reliable) metal concentrations in
the effluents. The findings the data showed highest concentration of Pb have maximum value
of 4.350mg/L against a mean level of 4.233±0.085mg/L (Table 3.3) for Hawassa textile
effluents and that of Arba Minch; the maximum concentration of Pb is about 1.200mg/L
against an average level of 0.933± 0.278mg/L relative to other heavy metals. This implies the
textile effluent and adjacent water bodies are highly contaminated by lead. The content of
lead in water samples of Lake Hawassa showed average value of 4.233±0.085mg/L against
the levels relatively unpolluted Chamo Lake were found 0.933±0.278 mg/L this may be the
contribution of dyeing and finishing process of Hawassa textile industry. Metal
concentrations in the water samples from both stations are shown in Table 3.3 & 3.4 to be
above the guide line limit.
Comparisons were made between the mean metal concentrations in waste water
samples before treatment and after treatment were tending to be similar and are above the
permitted level of the guideline limit. The average levels metal concentrations of both water
samples for Hawassa and Chamo lake were above permitted levels for drinking water (Fig
3.12, 3.13 & 3.14)26. From the evidence the levels of metals such as Cu, Pb and Cr arisen due
to textile effluents and other source to the natural environment.
4. CONCLUSIONS
The textile industry emits a wide variety of pollutants from all stages in the
processing of fibers and fabrics. Results from this study showed especially Hawassa textile
effluents were highly toxic not only for human beings living near affected areas but also a
serious threat to ground and surface water resources. It is clear that the effluent of Hawassa
textile industry is far from the prescribed limits, toxic in nature and requires treatment before
disposal on land as well as water because trace metals are too higher than the prescribed
limits and not safe for final release. These are the most frightening values and cause a real
threat to the environment27. These could mean the factory poses series pollution load to the
environment in general and the aquatic habitat in particular.
The concentration of these metals in all samples exceeded the prescribed guideline
limit. The wastewater treatment plant of the Hawassa textile factory is nominal as it is
inefficient for treating heavy metal. Therefore, the effluent demands frequent control and
proper treatment before being discharged to the environment and Proper legislation should be
done for all quality parameters of wastewater and should be implemented and monitored
regularly28.
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Tessema Bashaye Tafesse, et al., J. Chem. & Cheml. Sci. Vol.5 (4), 153-168 (2015)
167
ACKNOWLEDGEMENT
The authors are grateful to the Research Grant & Monitoring Directorate of Arba
Minch University for providing financial support through award of a minor research Project.
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