Impact of Municipal effluent on the water quality ofreceiving rivers: A case of River Aturukuku in Tororo

district, Eastern Uganda.Julius Matsiko, Jolocam Mbabazi and Muhammad Ntale*

Department of Chemistry, Makerere University P.O Box 7060 Kampala

Abstract

Physicochemical parameters (electrical conductivity, pH,

temperature, chemical oxygen demand, total suspended solids,

hardness, nitrate, nitrite, phosphate) were determined in water

samples collected from River Aturukuku in Tororo District,

Eastern Uganda. Selected heavy metals (Zinc, Copper, Lead and

Cadmium) were also determined using Atomic Absorption

Spectrophotometry. The aim was to study the effect of Tororo

municipal effluent on the water quality of River Aturukuku. These

determinations were made for both the dry (January 2011) and the

rainy (May 2011) seasons. The results from both dry and rainy

seasons were compared to determine the extent of pollution for

either season. In addition, the levels of pollution upstream and

downstream were also compared. Generally, lead was not detected

from most of the samples. Cadmium was not detected in all the

samples for all seasons. Results of a t – test showed that there

was a significant difference (p= 0.020 < 0.05) between the dry1

and rainy seasons for the physico chemical parameters and the

nutrients. The implication is that the river was more polluted in

the rainy season than dry season. Results for most parameters

were within the standard allowable limits such as those of WHO,

NEMA and USEPA and FMENV.

Key words; Tororo, Effluent, Water quality, River Aturukuku

INTRODUCTION

Many streams and rivers that are an important means of livelihood

for numerous communities have been converted into slow-moving,

polluted drains (Mbabazi et al., 2010 ). Most sewage (wastewater of

mainly domestic origin, containing among others, human excreta)

from urban areas and industrial wastewaters are discharged from

point sources. Industrial effluents account for several point

sources of water pollution (Awomeso et al., 2010). On the other

hand, runoff from large urban or agricultural catchments carrying

loads of sediments and nutrients is one of the examples of non-

point sources of water pollution. Virtually all categories of

water use contribute to pollution (Walakira, 2011).

2

*Corresponding author; mntale@chemistry.mak.ac.ug

The effect of Tororo municipal effluent on the water quality of

River Aturukuku, Eastern Uganda was investigated in this study.

The increase in population over the years has led to an increase

in the anthropogenic processes for example metal works, increase

in motor traffic, paintings with increase in building

construction, increase in car batteries’ disposal, electrical

wiring, waste water discharges from homes and increase in calcium

from limestone deposits. Nevertheless, the sources of domestic

water have remained constant, if not diminished.

With the rapid expansion of population and industrialization in

the town, Tororo is presently faced with mounting untreated

polluted effluent entering the receiving River Aturukuku. The

municipality is traversed by a network of underground pipes of

running water and piped water is pumped from River Malaba, around

eight to ten kilometres east of the town centre. Knowledge of the

current state of the quality of water at specific points in the

township was therefore essential, especially with regard to the

soluble and invisible inorganic pollutants, notably heavy or

trace metals. The study was therefore developed to make an

assessment in order to evaluate the prevailing situation and

3

provide accurate information on the water quality of River

Aturukuku using pollution indicators that would give basis for

appropriate waste-water management practices. Sewage treatment

takes place in the waste stabilisation ponds located one

kilometre along Mbale Road and the effluent is discharged

directly into a nearby River Aturukuku which is one of the easily

accessed sources of water for the rural population of Tororo.

The general objective of this investigation was to establish the

extent to which the water quality of River Aturukuku is affected

by Tororo municipal effluent both in dry and rainy seasons, as a

result of the increasing municipal industrial and anthropogenic

effluent wastewaters draining directly into the water-way.

Specifically, physicochemical parameters (Electrical conductivity

(EC), Temperature, pH, Total suspended solids (TSS), Chemical

oxygen demand (COD), nitrite, nitrate, ammonia nitrogen,

phosphate calcium (Hardness) and four selected heavy metals

(Cadmium, Lead, Zinc and Copper), were determined. Comparison of

the levels of pollution of the river water in the dry season with

the rainy season and upstream levels with downstream levels of

the physical chemical parameters was also done.

4

The need to establish the extent to which River Aturukuku is

polluted is because the effluents which are discharged therein

consist of many wastes which pose serious threat to the

environment, including human health risks. Therefore there is

need to control pollution of the availability of adequate

quantity of good quality water. Literature survey indicates that

no analytical work has been done on this river yet a bigger

percentage of the population in the district depends on its water

for domestic use. From the above information, it is obvious that

data on the quality of water in this stream is needed. The

findings of this study are expected to provide information that

will assist the district administrators and policy makers in

arriving at new and effective decisions about the management of

this river, create awareness among the natives of the land on how

to ensure that they use safe water despite the pollution and

provide analytical data on some of the river water parameters

upon which further research on the stream can be based.

MATERIALS AND METHODS

Study area

5

This study was carried out in River Aturukuku in the district ofTororo in eastern Uganda.

Figure 1: The schematic map of Tororo municipality with samplingpoints indicated in black.

Sampling procedure

One sample was collected up stream before the river enters the

municipality; other ten (10) samples were collected from ten (10)

points 200 metres apart as the river traverses through the

6

US

J

A

municipality. These samples were collected in triplicate both in

the dry and rainy seasons in order to get meaningful results for

all the parameters to be determined. The collection containers

(1000 ml each) were rinsed with the appropriate sample before the

final sample collection was made. The containers were tightly

closed and put in a bag after which they were taken to Makerere

University, Department of Chemistry and Department of Geology for

laboratory analyses. A few drops of concentrated nitric acid were

added to measured volumes to preserve the metals and also to

avoid precipitation.

Analytical methods

Analytical grade reagents bought from BDH (British Drug Houses)

Laboratory Suppliers and Westford Laboratory Supplies, Kampala

were used and double distilled water was used for preparation of

solutions.

Electrical conductivity was determined by a conductivity meter.

Temperature was determined by using the thermometric method. pH

was measured by a pH meter which was calibrated first by standard

buffer solutions. The total suspended solids in the water samples7

were determined by pouring carefully measured volumes of the

water (typically 100ml) through a pre-weighed Whatman No.40

filter paper. The filter paper and its contents were then dried

at 105 0 C. The gain in weight was taken to be the dry weight

measure of the particulates present in the water sample. Total

suspended matter was then determined by the following formula.

TSS mg/l = (final weight – initial weight)/volume of sample x

1000. (Anon, 1992). COD was determined using potassium dichromate

in the presence of concentrated sulphuric acid, mercury (II)

sulphate and silver sulphate catalysts. Nitrite, nitrate, ammonia

and phosphate concentrations were determined using the methods

described in the Wagtech manual. Hardness was determined by EDTA

titration (Harris, 2003). Heavy metal concentration was

determined using three methods so as to obtain values that would

yield more meaningful and representative results. In the first

case, the filtered samples were analysed directly without any

treatment (Kisamo, 2003), in the second case, to 250 ml of the

filtered water sample 5 ml of concentrated hydrochloric acid was

added and evaporated to 25 ml. The concentrate was then

transferred to a 50 ml flask and diluted to the mark with

8

distilled water. Metal contents were determined using the FAAS

(Olowu et al., 2010) to determine the presence of copper, zinc,

cadmium and lead. In the third case, at the time of analysis, 0.2

litres of the water samples from each site were evaporated to

dryness. To the residue, the acid system, namely concentrated

nitric acid (10 ml) and perchloric acid (2 ml) was then added.

The mixture was reheated to dryness. and the final residue was

then reconstituted in 2 ml of hydrochloric acid (2M),

transferred to a 25 ml volumetric flask and made up to the mark

with distilled water. The solution was analysed for copper, zinc,

cadmium and lead, using a flame atomic absorption

spectrophotometer, FAAS (Perkin_Elmer GmbH, Uberlingen, Germany.

Model 2380) and in each case, a read-out from the screen was

taken as the concentration of the selected metals. Data was

analysed by using Microsoft Excel, General Statistics and SPSS to

determine the level of significance.

9

RESULTS AND DISCUSSION

After the analyses, the results were obtained as shown in the tables 1 and 2 below for both the dry and rainy seasons.

Table 1: Average Levels of physicochemical parameters of the water samples in the dry season.

EC/ 302 246 284 284 292 288 314 362 662 279 250μS/cm ±0.82 ±1.63 ±0.82 ±0.8

2±0.82 ±1.63 ±2.4

5±0.82 ±1.63 ±2.49 ±1.63

Temp/ 24.7 24.5 24.5 24.6 24.7 24.7 24.5 24.5 24.6 24.7 24.50C ±.082 ±.082 ±.047 ±.08

2±.163 ±.082 ±.08

2±.082 ±.047 ±.082 ±.082

PH 6.96 7.12 7.12 7.24 7.33 7.45 7.51 7.42 7.32 7.49 7.56± 0.004

70.0082

0.0082

0.0047

0.0082

0.0082

0.0082

0.0124

0.0082

0.0082

0.0047

TSS/ 0.046 0.024 0.031 0.037

0.019 0.035 0.007

0.0077

0.014 0.0013

0.0013

mg/l± 0.0008

0.0008

0.0008

0.0008

0.0008

0.0013

0.0008

0.0012

0.0008

0.0005

0.0005

COD 100.00

30.00 23.33 23.33

26.67 103.33

23.33

140.00

143.33

96.67 20.00

mg/l ±8.16 ±8.16 ±4.71 ±4.71

±9.43 ±12.47

±4.71

±8.16 ±4.71 ±4.71 ±0.00

NH3 0.050 0.023 0.050 0.043

0.047 0.037 0.090

0.013 18.03 0.043 0.010

mg/l± 0.0082

0.0047

0.0082

0.0047

0.0047

0.0047

0.0082

0.0047

0.1248

0.0047

0.0000

NO3- 0.177 0.117 0.217 0.16 0.129 0.073 0.23 0.227 0.527 0.671 0.052

10

9 7mg/l± 0.000

820.00082

0.00082

0.0013

0.00082

0.0017

0.0012

0.0016

0.0013

0.00082

0.00047

NO2- 0.008

00.0013

0.0003

0.0003

0.0080

0.0003

0.0003

0.0013

0.0090

0.0003

0.0000

mg/l± 0.00082

0.00047

0.00040

0.00040

0.00082

0.00040

0.00040

0.00047

0.00082

0.00040

0.00000

PO43- 2.213 1.560 2.220 1.51

72.710 1.310 2.01

02.410 2.900 2.517 1.553

mg/l± 0.0125

0.0082

0.0163

0.0125

0.0082

0.0082

0.0082

0.0082

0.0082

0.0125

0.0047

HardnesS

92.00 95.00 94.00 97.00

88.33 100.70

113.00

132.33

157.00

154.00

91.00

mg/l ±0.82 ±0.82 ±0.82 ±0.82

±0.47 ±0.94 ±0.82

±0.47 ±0.82 ±0.82 ±0.82

Stations

A B C D E F G H I J US

Table 2: Average Levels of physicochemicalparameters in the water samples in the rainy season.

11

EC/ 240 240 250 260 260 260 301 300 309 301 210μS/cm ±0.82 ±1.63 ±1.63 ±0.00 ±0.82 ±1.63 ±0.82 ±0.82 ±0.82 ±1.41 ±0.00Temp/ 23.83 23.80 23.90 23.80 23.90 24.00 24.00 24.00 23.90 23.90 23.900C ±.047 ±.082 ±.082 ±.082 ±.082 ±.082 ±.163 ±.082 ±.082 ±.082 ±.082pH 6.54 6.60 6.63 6.62 6.66 6.71 6.69 6.70 6.69 6.73 6.87± 0.008

20.0082

0.0047

0.0047

0.0082

0.0082

0.0082

0.0082

0.0082

0.0082

0.0082

TSS/ 0.0990

0.1023

0.1030

0.1027

0.0650

0.0400

0.0280

0.0310

0.0300

0.0300

0.0450

mg/l± 0.0013

0.0012

0.0008

0.0005

0.0013

0.0008

0.0008

0.0008

0.0008

0.0008

0.0008

COD 123.3 83.33 123.3 80.0 360.0 1313.0

1513.3

310.0 1073.0

1273.0

320.0

mg/l ±12.47

±4.71 ±4.71 ±8.16 ±0.00 ±9.43 ±9.43 ±8.16 ±9.43 ±9.43 ±0.00

NH3 1.180 0.543 1.150 1.440 0.593 0.670 0.070 0.950 0.790 0.823 0.553mg/l± 0.008

20.0125

0.0082

0.0082

0.0125

0.0082

0.0082

0.0082

0.0082

0.0125

0.0047

NO3- 1.704 0.866 0.896 1.346 1.066 0.487 2.803 2.627 2.926 0.551 0.293

mg/l± 0.00082

0.00082

0.00082

0.00082

0.00082

0.00160

0.00210

0.00120

0.00130

0.00082

0.00082

NO2- 0.063

00.0590

0.0680

0.0570

0.0827

0.0370

0.0360

0.0943

0.0986

0.0643

0.0250

mg/l± 0.0016

0.0013

0.00082

0.00082

0.0012

0.00082

0.00082

0.0012

0.00047

0.00047

0.00082

PO43- 2.403 1.903 1.707 1.853 1.607 1.950 1.410 2.510 1.647 2.103 2.103

mg/l± 0.0125

0.0125

0.0170

0.0047

0.0047

0.0082

0.0082

0.0082

0.0047

0.0047

0.0047

HardnesS 96.00 108.00

103.00

113.30

115.00

119.70

137.33

131.00

108.00

136.00

90.33

mg/l ±0.82 ±0.82 ±0.82 ±1.25 ±0.82 ±1.25 ±0.94 ±0.82 ±0.82 ±0.82 ±0.47Stations

A B C D E F G H I J US

12

Table 3. Average Total heavy metal levels in the waters atvarious points along Aturukuku stream, Tororo town – EasternUgandaZn,DS

.1353

.0067

.0067

.0733

nd .0267

.0157

.0590

.0710

.0157

.0067

± .0115

.0041

.0041

.0059

nd .0059

.0047

.0125

.0047

.0047

.0000

RS

.2557

.0857

.0820

.2433

.3900

.3233

.3477

.2533

.0787

.2933

0.437

± .0070

.0043

.0059

.0059

.0059

.0070

.0059

.0047

.0047

.0126

.0047

Cu,DS

.0867

.0843

.0687

.6720

.0267

.0987

.0723

.0033

.0767

.0033

.0000

± .0085

.0070

.0031

.0152

.0031

.0085

.0043

.0021

.0059

.0021

.0000

RS

.0857

.0057

.1057

.0057

.0070

.0043

.1023

.0033

0.003

.0067

.0000

± .0096

.0029

.0125

.0029

.0024

.0035

.0070

.0021

.0040

.0041

.0000

Points

A B C D E F G H I J US

Cd,DS

nd nd Nd nd nd nd nd nd nd nd Nd

RS

nd nd Nd nd nd nd nd nd nd nd Nd

Pb,DS

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

13

RS

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

<.001

Table 4: Averages of the average parameter values compared withupstream average levelsParameter/Nutrient

Average of averageparameter values

Average Up stream levels

Dry season Rainyseason

Dry season Rainyseason

EC/µcm-1 323.88±1.41 266.45±0.95 250.00±1.63 210.00±0.00Temp/0C 24.60±0.083 23.90±0.086 24.50±0.086 23.90±0.082pH 7.32±0.0076 6.68±0.0076 7.56±0.0047 6.87±0.0082TSS/mgl-1 0.0203±0.00

08

0.0615±0.00

09

0.0013±0.00

05

0.045±0.000

8COD/mgl-1 of

02

66.36±6.36 597.48±6.90 20.00±0.00 320±0.000

Ammonia/mgl-1 0.0406±0.00 0.797±0.009 0.01±0.0000 0.553±0.004

14

53 1 7Nitrate/mgl-1 0.2361±0.00

11

1.4149±0.00

11

0.0523±0.00

05

0.2930±0.00

08Nitrite/mgl-1 0.00199±0.0

0049

0.0623±0.00

094

nd 0.0025±0.00

082Phosphate/

mgl-1

2.084±0.009

8

1.927±0.008

1

1.553±0.004

7

2.103±0.004

7COD/mgl-1 of

02

110.40±0.77 114.33±0.88 91.00±0.82 90.33±0.47

Physicochemical parameter levels of water samples collected from River Aturukuku in both dry and rainy seasons are displayed in tables 1 and 2 respectively.

Electrolytical conductivities were comparatively high, with

values ranging between 246 ± 1.63 and 362 ± 0.82 μS cm -1 in the

dry season (Table 1) and between 210 and 309 ± 0.82 μS cm -1 in

the rainy season, more than 6000 fold that of pure distilled

deionised water. This suggested a presence of more soluble ionic

substances, among them; metallic hydroxides, carbonates and

hydrogen carbonates that would in turn tend to buffer the waters

against excessive intrusive acidities and alkalinities. A higher

value of electrical conductivity (662 ± 1.63μScm-1) was observed

at sampling station I in the dry season implying that the

concentration of the dissolved inorganic substances in ionized15

form was high as at this point; the effluent from the treatment

ponds enters into the river directly at this point. There was a

general decrease in average electrical conductivity that is, from

323.88 ± 1.41 μScm-1 in the dry season to 266.45 ± 0.95 μScm-1 in

the rainy season (Table 4). This is attributed to the decrease in

number of conducting ions per unit area in the rainy season. In

other words, there was dilution of the salts arising from the

increased water volumes in the river (Phiri et al., 2005). Values

obtained for all the samples were within the permissible limits

of US – EPA , WHO, NEMA and FMENV of 400, 300, 400 and 400 μScm-1

respectively (Khan and Khan, 1985).

The average values of water temperature for both dry and rainy

seasons respectively, ranged between 24.5 ± 0.082 and 24.7 ±

0.082 0C and between 23.83 ± 0.047 and 24 ± 0.082 0C (Tables 1

and 2) which is within the FEPA permissible limit of less than

400 C (Olajumoke et al., 2010). There was a general decrease in

temperature that is from 24.60 ± 0.083 0C in the dry season to

23.90 ± 0.086 0C in the rainy season (Table 4). This might be due

to an increased amount of effluents entering into the river. The

property of water is that with change in temperature, it’s16

density varies and it becomes less with warming up and more with

cooling (Murhekar, 2011). Temperature readings for all the

samples were above the WHO standard value of 12 0C.

The pH of the filtered water samples at 25°C was in the range

6.963 ± 0.0047 to 7.557± 0.0047 in the dry season and 6.54 ±

0.0082 to 6.87 ± 0.0082 in the rainy season (Table 1 and 2) which

was indicative of the relative neutrality, in spite of the direct

seepage of the untreated municipal effluent, into the stream

waters. These ranges are in line with the FEPA/FMENV(Federal

Environmental Protection Agency /Federal Ministry of Environment,

1991), permissible limit (Olajumoke et al., 2010), WHO, US – EPA

and NEMA of 6.5 – 8.5, 6.5 – 9.2, 6.0 – 8.5 and 6.0 – 8.0

respectively. There was a general decrease in pH that is from

7.32±0.0076 in the dry season to 6.68±0.0076 in the rainy season

(Table 4). The relatively lower values of pH in the rainy season

could be due to a combined effect of the effluent and some

incoming fertilizers such as ammonium nitrate and urea from the

farming areas due to run off (Phiri et al., 2005).

17

Despite the relative neutrality of the waters, water samples in

the rainy season were acidic implying that they may not be

favourable to the existence of bacteria in the river (Aremu et al.,

2011).

The levels of the Total suspended solids (TSS) (Tables 1 and 2)

were in the range of 0.0013±0.0005 to 0.046±0.0008 mgl-1 in the

dry season and 0.028±0.0008 to 0.1027±0.0005 mgl-1 in the rainy

season. There was a general increase in the levels of the Total

suspended solids (TSS) that is from 0.0203±0.00083 mgl-1 in the

dry season to 0.0615±0.0009 mgl-1 in the rainy season (Table 4).

The values obtained for all the samples were within WHO and FMENV

limits of 5 and 0 – 5 mg/l. Water containing high levels of TSS

is not suitable for aquatic life (Olajumoke et al., 2010) and

human consumption. In the dry season, the levels of the total

suspended solids were lower and this can be attributed to the

fact that the water was free from materials that could be brought

into the river through runoff (Phiri et al., 2005). In the rainy

season, the degree of runoff is high and this is the reason for

the increased levels of total suspended solids (TSS).

18

The values of COD (Tables 1 and 2) ranged from 23.33±4.71 to

143.3±4.71 mgO2l-1 in the dry season and from 80±8.16 to

1513.3±9.43 mgO2l-1 in the rainy season. There was a sharp

increase in COD values from 66.36 ±6.36 in the dry season to

597.48±6.90 mg(O2) l-1 (Table 4). For all the water samples the

values of COD obtained are above the maximum allowable limits

according to WHO and US – EPA of 10 – 20 and 10 mg/l. However

some samples for example at points A,B.C,D,E,J and US in the dry

season and points B and D in the rainy season were within the

limits of NEMA drinking water standard of 100 mg/l. High values

of COD make the water to have objectionable odour, render the

water unfit for domestic purpose and reduce oxygen available for

aquatic organisms.

The values of ammonia (Tables 1 and 2) obtained ranged from 0.01

to 0.09±0.0082 mgl-1 in the dry season and from 0.07±0.0082 to

1.44±0.0082 mgl-1 in the rainy season. There was a sharp increase

in the concentration of ammonia that is from 0.0406±0.0053 to

0.797±0.0091 mgl-1 in the rainy season (Table 4). In the rainy

season, runoff from the municipality increased in which a lot of

19

nitrogen containing compounds were entering directly into the

river.

The levels of nitrate concentration (Tables 1 and 2) ranged from

0.0523±0.00047 to 0.671±0.00082 mgl-1 in the dry season and from

0.293±0.00082 to 2.8027±0.0021 mgl-1 in the rainy season. There

was a general increase in nitrate average concentration that is

from 0.2361±0.0011 in the dry season to 1.4149±0.0011 mgl-1 in

the rainy season (Table 4). For all the samples, the values

obtained were within the WHO and US – EPA permitted limits for

drinking water of 45 and 100 mg/l. In the dry season, the

concentration of the nitrate was at a lower level possibly

because there was little or no run - off at all. In the rainy

season, the concentration of the nitrate increased possibly as a

result of water run – off through the application of fertilizers

and pesticides (Phiri et al., 2005; Aremu et al., 2011) by the host

communities since farming is carried out along and around the

river.

Nitrite concentration (Tables 1 and 2) ranged between 0.000 to

0.009±0.00082 mgl-1 in the dry season and from 0.025±0.00082 to

20

0.0986±0.00047 mgl-1 in the rainy season. There was a sharp

increase in average nitrite concentration that is from

0.00199±0.00049 mgl-1 in the dry season to 0.0623±0.00094 mgl-1 in

the rainy season (Table 4). The results obtained for all the

samples were within the limits of NEMA maximum allowable value of

3 mg/l. In the rainy season, run off from the municipality, farms

and from other water channels increases and all the effluent

enters the river directly. This is responsible for the elevated

concentration of the nitrite.

The concentration levels of the phosphate (Tables 1 and 2) ranged

from 1.31±0.0082 to 2.90±0.0082 mgl-1 in the dry season and from

1.41±0.0082 to 2.51±0.0082 mgl-1 in the rainy season. There was a

slight decrease in phosphate concentration that is from

2.084±0.0098 mgl-1 in the dry season to 1.927±0.0081 mgl-1 in the

rainy season (Table 4). The concentration levels of phosphate in

the dry and rainy seasons are almost the same probably because

the contamination with phosphate was equally likely in both

seasons and this could be attributed to atmospheric phosperous.

21

The levels of hardness (Tables 1 and 2) were in the range of

91±0.82 to 157±0.82 mgCaCO3l-1 in the dry season and 90.333±0.47

to 137.33±0.47 mgCaCO3l-1 in the rainy season as compared with the

WHO and US – EPA permissible limit of 100 mgCaCO3l-1. People with

kidney and bladder stones should avoid high content of calcium

and magnesium in water (Olajumoke et al., 2010). Water has been

classified on the basis of hardness as follows: water having (0 –

75) mgCaCO3l-1 as soft, for (75 – 150) mgCaCO3l-1 as hard and for >

300 mgCaCO3l-1 as totally hard (Adeyeye and Abulude, 2004).

Therefore basing on this, water in River Aturukuku varied between

moderately soft and slightly hard for almost all the water

samples apart from the samples at point I in the dry season where

the level of hardness was 157±0.82 mgCaCO3l-1(water was moderately

hard). There was a slight increase in the levels of hardness that

is from 110.40±0.77 mgCaCO3l-1 in the dry season to 114.33±0.88

mgCaCO3l-1 (Table 4). Activities such as farming, bathing and

washing of clothes by villagers along and around the river could

also account for the relatively high levels of hardness.

The levels of trace metals determined in the water samples aredisplayed in Table 3. The total concentration, in mg l−1, of the

22

metals in all the samples decreased in the order: Zn > Cu> Pb >>Cd.

The total average zinc concentration (Table 3) in the filtered

water was found to be the highest in all the samples. It ranged

from nd to 0.1353±0.0115 mgl-1 in the dry season and from 0.0787

±0.0047 to 0.3900±0.0059 mgl-1 in the rainy season. There was a

sharp increase in the concentration of zinc that is from

0.0379±0.0058 mgl-1 in the dry season to 0.2536±0.0064 mgl-1 in

the rainy season. Values obtained for all the samples were in

line with the WHO, NEMA, USEPA and FMENV limits of 5,5, 5 and <1

mg/l. Whereas zinc is a naturally occurring metal and was

expected to be present in low levels in river water, its notable

presence in the river is most probably due to several major

factors. Currently, the building construction industry has

increased tremendously in the town, with an extraordinary demand

for wall and roof paints, most of which are zinc-based. The

result is an increased release of zinc into the urban

environment, which finds its way into the municipality’s major

drainage system and then to the river. Zinc-coated corrugated

iron sheets, the commonest roofing material in the country, on

23

corrosion release considerable amounts of zinc as its oxide or

sulphide into the soil, the leaching of which concentrates the

metal in the water body via surface run-off and other processes.

Copper in the samples (Table 3) gave mean total concentrations of

0.000 to 0.0867±0.0085mg l−1 in the dry season and 0.000 to

0.1023±0.0070 mg l−1 in the rainy season. Copper was more or less

evenly distributed among all the sites (US to J), with the total

metal concentrations lying in the range 0.0–0.13 mg l−1 over the

entire study period apart from the samples obtained from point D

in the dry season where the average concentration of copper was

0.672mg/l. For all the samples, the values obtained are within

the limits of NEMA drinking water standards. The presence of a

rather elevated copper content in the water along the Aturukuku

river in Tororo municipality may at first sight not be easily

understood. Increased usage of imported electrical copper wire

and cables in the town leaves on a daily basis a considerable

amount of waste metal in the form of bits, choppings and cut-

offs. Metallic copper washed down in the run-offs subsequently

24

dissolves in the fluctuating acidities and alkalinities of the

effluent.

The total lead concentrations in the samples (Table 3) were in

the range 0.000 – 0.001 mg l−1. In fact, the findings from the

study showed that lead was not detected from most of the samples

both in the dry and the rainy seasons. However, for some samples

the maximum concentration was 0.001mgl-1 which is within the WHO

and FMENV permissible limits of 0.05 mg/l. The presence of this

toxic metal in the river waters either as free cations or as

associations with organic matter could be attributed to several

factors, which include the continued use of lead-based paints for

face-lifting buildings in the town and their inappropriate

disposal. In addition, there is poor management of industrial and

municipal waste. Car washing and emptying of dead lead-acid

accumulators regularly takes place directly along the streams and

channels leading to the river (Mbabazi et al., 2010 ) and even

along the river itself especially on a bridge which is along

Mbale road, 1km from the town centre. The untreated lead laden

effluent discharges directly into the river waters. From the turn

25

of the century, the volume of motor vehicles on Tororo roads has

greatly increased on the busy streets, especially the Tororo High

Street. Although unleaded petrol is available at fuel pump

stations in the country, a number of operators and drivers do not

insist on it. The gradual shift to the use of unleaded petrol

should lead to a reduction or elimination of the release of lead

into the urban atmosphere.

Cadmium was not detected in all the samples for all seasons. This

probably can be attributed to the fact that the activities of

small-scale metal works in the town, which process even scrap

metal and run their untreated effluent directly into the drainage

channels could still be at a stage where the amount of cadmium is

still below the detectable limits. Traces of cadmium embedded in

the scrap iron and steel are released to the environment in the

effluent and run-off. If this continues, soon cadmium levels will

soon be detected. Further, cadmium is widely used in paints, and,

owing to the booming construction in the town, there is a

considerable release of the metal into the environment via the

associated painting and face-lifting of buildings. Cadmium has

been blamed for large-scale poisoning incidents in industrial

26

workplaces, particularly where any ore is being processed or

smelted and among welders who have unsuspectingly welded on

cadmium-containing alloys or working with silver.

Conclusions

Tororo town relies partly on River Aturukuku for its drainage of

wastewater, runoff and industrial or other effluent. The

analytical results obtained show that the levels of heavy metals

in the river water are on the rise, which is reflective of the

growing anthropogenic pollution problem in the town. The results

further suggest that effluents being discharged into the river

have considerable negative effects on the water quality in the

river though the values obtained are in the acceptable ranges for

most of the parameters. A comparison of upstream and downstream

levels indicates that pollution levels increase as the river

traverses the municipality. This poses a big threat to this

reliable source of fresh water for domestic and industrial use.

Acknowledgements.

27

Authors are grateful to DAAD and Carnegie Corporation for funding

this research project.

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