Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

118

Assessment of Heavy Metals in Borkena River in South Wollo

Ethiopia

Alemu Mengesha

and Omprakash Sahu

1- Department of Chemistry, NSC Wollo University (SW) Ethiopia

2- Department of Chemical Engineering, KIOT Wollo University (SW) Ethiopia

Received: 02/12/2014 Accepted: 06/03/2015 Published: 30/06/2015

Abstract

Trace elements concentration in Borkena River was investigated, as they can deteriorate water quality. Levels of Lead

(Pb) and Cadmium (Cd) in river water and industrial effluents taken from 3 industries found in Kombolcha were

determined by differential pulse anodic striping voltammetry. The river water down the site, where effluents join, had

significantly higher concentration of Pb and Cd than did the water above the drainage system. The concentration of Pb and

Cd in river water down the site where effluents join were found to be above the permissible limit values of WHO and

FAO. The highest contributor was KOSPI: BGI and Textile was the second and third interns of Pb content. The water

supply for domestic purpose and irrigation from the river down the site where the drainage system joins were note safe.

Keywords: Heavy metal analysis, Borkena River, Anodic Striping Voltammetry, Industrial Effluents

1 Introduction

Generally industrial or municipal wastes, containing

different chemicals, are disposed to water bodies such as

lakes, oceans and rivers as water is considered as

universal solvent [1]. The chemical contamination of

drinking water leads to health problems primarily

through chronic exposure, as it may persist for years

before detection [2]. In many countries the major

chemical pollutant of surface water comes from

industrial and municipal sewages as municipalities of

cities lacks sufficient waste treatment facilities [3].

Sometimes the corrosion of the urban water supply

system also contributes heavy metal contamination of

water [5]. The preservation and maintenance of natural

water resources is a burning issue. The quality of water

resources is deteriorating day by day due to continuous

discharge of municipal and industrial effluents. On the

other hand, the demand for safe water is increasing

continuously due to the increase in population, living

standard and industrialization [6]. The discharges from

many industrial wastes contain various organic and

inorganic water contaminants including higher level of

toxic heavy metals like Pb, Cd, Zn, Cu and others.

Among the various water bodies river water is the most

exposed for pollution due to the direct discharge of

municipal and industrial effluents to rivers. Under ground

water in the vicinity different drain systems also can be

polluted by toxic metals contamination from industrial,

domestic, mining and others waste discharges [3-5].

Among the various metal ions Pb, Cd and Hg are toxic at

all concentration level and have no known functions. The

metal ions of Cu, Zn, Co and Fe are required for

physiological and cellular activities but toxic above a

certain level [7, 8]. Toxic metals as they are non-

Correspondence author: Omprakash Sahu, Department

of Chemical Engineering, KIOT Wollo University (SW)

Ethiopia, Email:ops0121@gmail.com,

Tel: +251933520653.

degradable and bio-accumulative, cause tissue

degradation in nature [9, 10].

In literature different method has been suggested by

author as well some standard method are also available in

which Voltammetric is one of them. Voltammetric

method was first introduced by Heyrovsky in 1992, it

also known as Polarography. Polarography is a special

case of voltammetry referring to the current voltage

measurement acquired using a dropping mercury

electrode (DME) with a constant flow of mercury drops.

Voltammetry today represents a refined technique that

offers wide limits of detection and is used for trace

analysis [3]. Voltammetric techniques offer a number of

analytical advantages in environmental analysis [11, 12].

These includes, applicability to a wide range of

substances, high sensitivity with a linear concentration

range of analyse (10

-12

to 10

-1

M), tremendous number of

useful solvents and electrolyte, ease of automation, the

capability of determining more than one species at a

time, a well-developed theory which allows to reasonably

estimate the values of unknown parameters, and the ease

with which different potential wave forms can be

generated and small currents are measured. With

impactive impression toward the analyses pollution, it

was decided to dected the heavy metal in Broken River

by Voltammetric method. The river originates from Tosa

Mountain, which is located few kilometres from Dessie

town in South Wollo of Amhara region, Ethiopia, and

flows down to Kombolcha. Borkena River crosses the

plane of Kalu, Kemissie and finally joins to Awash River

in Afar region. Thousands of people are dependent on the

water of Borkena River and play vital role. The river is

used for irrigation, drinking and common household

purposes in the towns including Kombolcha, Harbu,

Dawa Chefa and Kemisie.

The main objective of this study is to investigate the

pollution potential of industrial effluents on the river by

considering the targeted toxic metal pollution status of

the river and point sources of the effluents.

Journal web link: http://www.jett.dormaj.com

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

119

2 Material and methods

2.1 Material

2.1.1 Chemicals

Nitrate salts of Pb

and Cd

(Blulux), concentrated

HNO

(LOBA), NaOH (Blulux), sodium acetate

(Blulux), acetic acid (Blulux ) and distilled water were

used through the experiment.

2.1.2 Apparatus

Voltammetric determination of Cd

and Pb

was

performed with BAS 100B, electrochemical analyzer

connected with Dell computer. Three-electrode

electrochemical system consisting of a glassy carbon

working electrode (radius =1.5 mm), a platinum wire as

counter electrode and an Ag/AgCl reference electrode

were used. The glassy carbon electrode was polished

with alumina (0.05 μM) and rinsed with distilled water

after each run. To measure the pH of solutions a Jenway

digital model 3305 pH meter with a combination of glass

electrode were used. Plastic bottles (HDPE), filter paper,

electrochemical glass cell were used in the experiment.

2.2 Methods

2.2.1 Preparations of Standard Solutions

(a) Lead (Pb): A 0.1599 g of Pb(NO

)

was dissolved

in 200 mL of distilled water; 10 mL of

concentrated HNO

was added and the solution was

diluted to the mark of 500 mL volumetric flask.

(b) Cadmium (Cd): A 0.2744 g of Cd (NO3)2.4H2O

was dissolved in 200 mL of distilled water, 10 mL

of concentrated HNO

was added and the solution

was diluted to the mark of 0.5 L volumetric flask.

The prepared stock solutions were containing 200

mg/L of the targeted metal ions. Standard solutions

were prepared by series of dilutions of the stock

solutions daily.

was prepared by dissolving 8.2 g of sodium acetate

in 0.8 mL of distilled water and by adding 5.75 mL

of acetic acid ( CH

COOH). The pH of the buffer

solution was adjusted by adding drops of

concentrated HNO

or NaOH. The HNO

was also

used to acidify the sample which prevents

adsorption of the metal ions on the wall of the

container. Distilled water was used to prepare

solutions and to clean equipments.

2.2.2 Sampling

From five sites, a total of seventeen composite

samples were collected in clean high density

polyethylene (HDPE) bottles within a week. Seven

industrial effluent samples were collected from the outlet

of the tankers of KOSPI, BGI and Textile factories

according to the schedule of discharge for a week. In

order to study the net contamination potential of the

industrial wastes at Kombolcha on the river, two sets of

samples (five bottles for each) were collected from sites;

i) Borkena Before the drain system of Effluents join the

river (BOBE); ii) Borkena After the drain system of

effluents join the river (BOAE). During sampling, the

bottles were first filled and rinsed three times with the

sample before collecting some for analysis and a grab

sample at each site was collected within 12 hours of a

day with 30 minutes intervals. Besides, tap water sample

from physical chemistry research laboratory of Bahir Dar

University was probed for the toxic metals ions of Pb and

Cd.

2.2.3 Sample Preparation

The samples were filtered through 0.45 μm

membrane filter into a beaker and acidified by adding

concentrated HNO

to the pH of 2. The acidified filtrate

was cooled in a refrigerator until analysis to avoid

variation in composition [13- 17]. Substantial

concentrations of organic materials in samples hinder the

electro chemical analysis of metal ions by forming stable

complexes with metal and by adsorbing on the electrode

surface. To avoid the interference acid digestion of the

samples was used. A 50 mL of the acidified sample and

10 mL of concentrated nitric acid in an Erlenmeyer flask

was heated on a hot plate for 2 hours. The light-colored

solution was cooled and filtered into 50 mL volumetric

flask and diluted to the mark. These digested samples

were preserved in refrigerator for analysis.

2.2.4 Procedures

In a typical differential pulse anodic striping

voltammetry, 10 mL of a 0.1 M acetate buffer and 10 mL

of sample were transferred to a clean cell. After the

operating parameters of DPASV have been adjusted the

solution was sprayed with nitrogen for 5 min. The

operating parameters are given in Table 1.

Table 1: Operating parameter of Voltammetry

S.No

Parameters

Description

Mode

Differential Pulse

Calibration

Standard Addition

Purge Time

180s

Deposition Time

300s

Quite Time

30s

Depositions Potential

-1V

Pulse Amplitude

50mV

Pulse Width

50ms

Initial Potential

-1V

Finial Potential

-0.2V

Sweep Rate

15mV/s

The metal ions of Pb and Cd were deposited by

reduction at - 1.0 V on a bare glassy carbon electrode

surface. The deposited metals were oxidized by scanning

the potential of the electrode from -1.0 to - 0.2 V using

differential pulse model.

The voltammogram of the sample were recorded and

the procedure was repeated after addition of standard

solution of the targeted metal ions. The quantification

and determination of sensitivity for Pb (II) and Cd (II)

were accomplished by standard addition to the sample.

The peak currents of each metal in the sample, and after

standard addition were recorded for calibration and

quantification. This method was preferred as the

sensitivity of differential pulse striping voltammetry

analysis varies between samples of different ionic

strength [5, 10, 18].

The activity coefficient and the diffusion current

constant of metal ions vary with the matrix of the

solution. As the rates of diffusion and the activity

coefficients of the analyses vary with composition of the

sample, the signal produced by a given analyse changes

as the matrix changes. The sensitivity, the magnitude of

peak current produced per 1pp, of metal ion in standard

and samples of different composition can vary

substantially [13, 19-20]. A basic issue that must be

considered for all calibration procedures is the matrix

effects on the analyse signal. The advantage of standard

addition method in both qualitative and quantitative

analysis is that all measurements, (E½, ip), are made in

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

120

the same matrix [19]. Hence, as the calibration –curves,

as well as, the sensitivity of analyses is strongly affected

by the matrix of the solution standard addition method is

preferred over the method of calibration using standard

solution alone [18, 19].

3 Results and Discussion

3.1 Mechanism of Voltammetric

The common characteristics of all Voltammetric

techniques is the application of a potential (E) to an

electrode and monitoring of current for chemical

analysis. In voltammetry method the potential is varied

or the current is recorded over a period of time (t). Thus

the current response is used to qualitatively and

quantitatively characterize the electro-active species. The

current (i) is plotted as a function of an applied potential

wave form. The magnitude of the peak current (ip) is

proportional to the concentration of the analysis. In each

Voltammetric waves, the current increases at the

reduction or oxidation potential of the analysis. The

measure of the peak currents forms the basis of

quantitative analysis. The maximum current is

proportional to concentration and the rate of diffusion of

analyses from the solution to the electrode surface. The

potential at which the diffusion current reaches half of

the limiting values is known as the half-wave potential

1/2

).It is characteristic of the particular electro- active

species involved and used for qualitative analysis of

metal ions [18,19]. Half wave potential (E

1/2

) for

reduction of metal ions can be expressed by equation (1)

ln ln

D nF

E E KC

  

Where; Eo is the standard reduction potential, n is

number of electrons, D

is diffusion coefficient of

oxidized specie, D

is diffusion coefficient of reduced

specie. When current is generated because of reduction

or oxidation reaction at the WE, a counter reaction takes

place at the CE. The analyses in the bulk diffuse to the

surface of the WE and undergo reduction or oxidation

reaction. The current generated due to this reaction

provides chemical information about the analyse. The

fundamental principles and applications of the various

types of Voltammetric techniques are derived from the

same electrochemical theory [21]

3.2 Analysis of Industrial Effluent Samples

3.2.1 Textile Effluent Samples

Three samples collected on different days at the point

source of textile effluent site were probed for Pb (II) and

Cd (II). Only Pb was found at detectable concentration.

In Fig. 1 the DPAS voltammogram for Pb obtained from

standard addition in the textile sample. The net current of

Pb (II) value in the sample was 12.75 μA and the

reduction potential was observed at - 0. 44 V. The peak

current was increasing proportionally with the

concentration of Pb in standard addition.

The successive addition of standard solution did not

bring significant potential peak shifts or any other

changes to the voltammogram, except an increase in peak

currents. The peaks of Pb (II) were reasonably symmetric

with narrow bas widths. The calibration curve of the peak

current as a function of Pb (II) concentrations in solution

during standard addition was linear with correlation

coefficient (R) = 0.993 as shown in Fig. 2. From the

intercept of this line with concentration axis at zero

current signals, the concentration of Pb (II) in the sample

can be calculated.

Fig.1: Differential pulse anodic striping voltammogram for textile

effluent sample spiked with standard Pb (II) solution: a) 10 mL of acetate

buffer + 10 mL of sample, b) a +100 µL of 10 mg/L standard Pb solution,

c) a + 150 µL of 10 mg/L standard Pb solution, d) a + 200 µL of 10 mg/L

standard Pb solution, e) a + 250 µL of 10 mg/L standard Pb solution.

Fig.2: Plot of peak current as a function of concentration for Pb (II)

obtained by standard addition method in textile sample.

In the three samples from the same site similar peak

currents and average Pb (II) concentrations were

obtained. The average Pb (II) concentration determined

from the intercept and R value of the calibration plot was

134 ± 3 μg /L.

3.2.2 BGI Effluent Samples

Based on the waste disposal schedule, after the waste

has been passed the treatment system three effluent

samples were collected at a point source of BGI. These

different samples were analyzed for detection of Pb (II)

and Cd (II) by differential pulse anodic stripping

Voltammetry. From the three samples only Pb (II) was

found. In Fig. 3 the DPAS voltammogram of Pb in three

BGI effluent samples. The voltammogram of each

sample were broad with different peak currents as

indicated in the figure. The reduction potential of Pb (II)

was observed at - 0. 42 V and the average peak current

was 23 μA. The magnitude of the peak currents of

sample two was higher than that of sample three and

sample one. But the sensitivity for Pb (II) in each sample

was identical.

Based on their peak currents, sample two has the

highest Pb (II) concentration and sample one has the

least. The average concentration of Pb (II) calculated

from the sensitivity determined by single standard

addition method and from the peak currents of each

sample was found to be 241± 5 μg /L. The sensitivity of

the technique for Pb in these samples was 95.2 nAL/μg

and current produced by 1 μg/L of Pb in the solution. To

determine the sensitivity a single standard addition

-0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Current (mA)

Potential (V) vs. Ag/AgCl

y = 0.0923x + 11.625

R² = 0.9955

-200 -100 0 100 200 300

Current (µA)

Concentration (µg/L)

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

121

method was used: the current produced before and after

spiking with 10 mg/L of Pb solution were recorded and

the proportion was set from the change in concentration

and current produced. The plot of peak current for

function of concentration shown in Fig. 4.

Fig.3:Differential pulse anodic stripping voltammograms for three BGI

effluentsamples in 0.1 M acetate buffer at pH = 4.5; a) sample 1 b)

sample 3 c) sample 2

Fig.4: Plot of peak current as a function of concentration for Pb (II)

obtained by standard addition method in BGI sample.

In the three samples from the same site similar peak

currents and average Pb (II) concentrations were

obtained. The average Pb (II) concentration determined

from the intercept and R value of the calibration plot was

241 ± 5 μg /L.

3.2.3 KOSPI Effluent Samples

A bottle of composite sample from the point source

was analyzed for determination of Pb (II) and Cd (II).

The DPAS voltammogram for KOSPI waste water

sample obtained from standard addition technique is

shown in Fig. 5. Both Pb (II) and Cd (II) were detected in

this sample. The Cd striping peaks in the sample, and

after spiked with standard solution, were symmetric with

narrow bas widths. The peak current increases rapidly

during each spike. However, the Pb stripping peaks were

asymmetric with slow increment of peak current as it can

be seen in the voltammogram.

Though the sensitivities were different, the peak

currents of both Pb and Cd were increased proportionally

with the solution concentration. Fig.6 and Fig.7 show the

standard addition curves of peak current versus

concentration of Cd (II) and Pb (II), respectively.

Fig.5:Differntial pulse anodic stripping voltammogram for KOSPI waste

water sample spiked with the standared solution of Cd (II) and Pb (II)

(10 mg/L each) : a) 10 mL of acetate buffer + 10 mL of sample, b) a +

100 µL of 10 mg /L standard solution, c) a + 200 µL of 10 mg/L standard

solution, d) a + 250 µL of 10 mg/L standard solution.

Fig. 6: Plot of peak current as a function of concentration for Cd

obtained by standard addition method in KOSPI sample.

Good linearity of peak current and concentration of

the standard added was observed for Cd (II). The

concentration of Cd in the sample was calculated from

the magnitude of intercept on the negative X-axis and

from the linear regression correlation coefficient (R =

0.998). The quotient of the intercept and R value gives

the concentration.

Fig 7: Plot of peak current as a function of concentration for Pb

obtained by standard addition method in KOSPI sample.

The linearity of the response and added concentration

of Pb (II) was observed with regression coefficient of

0.999. In the calibration, the sensitivity of voltammetry

for Pb and Cd were 8.95 nA L/μg and 107.5 nAL/μg,

respectively. In this sample the Pb sensitivity was much

less than that of Cd. From the intercepts and correlation

coefficients of the two calibration graphs the

concentrations of Pb and Cd in KOSPI sample were

determined to be 514.4 ± 4 and 251 ± 5 μg /L,

respectively.

-0.6 -0.5 -0.4 -0.3 -0.2

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Current (mA)

Potential (V) vs. Ag/AgCl

y = 0.0923x + 11.625

R² = 0.9955

-200 -100 0 100 200 300

Current (µA)

Concentration (µg/L)

-1.0 -0.8 -0.6 -0.4 -0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Current (mA)

Potential (V) vs. Ag/AgCl

y = 1.0509x + 263.76

R² = 0.9974

100

200

300

400

500

600

-300 -200 -100 0 100 200 300

Current (µA)

Concentration (µg /L)

251

y = 0.0093x + 4.7207

R² = 0.999

-600 -400 -200 0 200 400

Current (µA)

Concentration (µg /L)

514

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

122

3.3 The Borkena River Water Samples

The level of Pb and Cd were also measured in ten

water samples of Borkena River. In order to see the net

impact of the industrial wastes at Kombolcha two

locations in the river were chosen on the basis of the

reach of the industrial effluents into the river.

3.3.1 Borkena River before effluents joins the river

(BOBE)

A total of five water samples from BOBE, were

analyzed by DPASV. In these samples well-defined

stripping peaks for Pb and Cd were observed. Fig. 8

shows the DPAS voltammogram for Borkena River

water sample at the site before the industrial drain

systems join the river. The peaks for both metals in the

sample, as well after spiking, were symmetric with

narrow bas width. The reduction potentials for Pb (II)

and Cd (II) were observed at - 0.41 V and -0.56V with a

corresponding maximum net current values of 0.47 and

0.8 μA.

Fig.8: Differential pulse anodic stripping voltammogram for Pb and Cd

in water sample of Borkena River, at the site before the efflents mix

(BOBE), spiked with standard Pb (II) and Cd (II) solution : a) 10 mL

of acetate buffer + 10 mL of sample, b) a + 100 µL of 1 mg/L standard

Pb and Cd solution, c) a + 150 µL of 1 mg/L standard Pb and Cd

solution.

The reduction potential of Cd (II) in these samples

shift from the expected value, (-0. 59 V) by a 0.03 V. But

because of the complex formation and variation in

activity coefficient, the reduction potential of metal ion

can vary over one volt depending on the matrix of the

solution [5, 12]. Besides as the surface coverage and

adsorption of a metal deposit on the electrode change, the

reduction potential of a given metal ion can vary with

concentration. The most important advantage of

electrochemical techniques to assure a given analyse at

the observed potential is standard addition method [12].

As the analysis was done in the same matrix and from the

increment of peak current with standard Cd addition, it is

an obvious logic that the given analyse is Cd. The

standard addition peak currents for both Pb (II) and Cd

(II) were increased proportional to concentration. The

linear relation of the peak currents and concentrations of

added Pb (II) and Cd (II) are shown in Fig.9 and Fig.10

respectively.

The plot of peak currents against concentration of Pb

(II) added was linear with regression correlation

coefficient of 0.998.

Good linearity of peak current and concentration of

Cd (II) was observed with correlation coefficient of

regression 0.999. The concentration of each metal was

calculated from the intercept on the negative x axis and

from the correlation coefficients. The concentrations of

Pb and Cd are 21.7 and 3.95μg/L, respectively. The

calibration curves of peak current as a function of

concentration for each metal were linear with correlation

coefficient R= 0.999.

Fig. 9: Plot of peak current as a function of concentration for Pb

obtained by standard addition method in BOBE sample.

Fig. 10: Calibration plot of peak current as a function of

concentration for Cd obtained by standard addition method in BOBE

sample.

3.3.2 Borkena River after the effluents joins the river

(BRAE)

Five water samples of Borkena River at the junction

point of the river and the industrial effluent drain system

were analyzed. Fig.11 shows the DPAS voltammogram

of Pb and Cd in BOBE and BOAE samples

-0.8 -0.6 -0.4 -0.2

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Current (mA)

Potential (V)

Fig. 11: Differential pulse anodic stripping voltammogram for Pb and Cd

in water sample of Borkena River at two differen sites a) BOAE b)

BOBE

As it can be seen from the figure, the potentials of Cd

and Pb in BOBE and BOAE samples show shift from

each other. This is due to variation of the matrix of

solutions in the two sets of samples. Though it is not

possible to know the exact composition, the BOAE

samples should contain several complexing agents

disposed with industries wastes. However, both the

-0.8 -0.6 -0.4 -0.2

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Current (mA)

Potential(V) vs. Ag/AgCl

y = 0.0202x + 0.4296

R² = 0.9989

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-30 -20 -10 0 10 20 30

Current (µA)

Concentration (µg /L)

21.7

y = 0.215x + 0.8497

R² = 0.9991

-10 -5 0 5 10 15 20 25

Current (µA)

Concentration (µg /L)

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

123

relative and the absolute reduction potential shifts

observed are insignificant as compared with the

maximum potential shift suggested from variation of

matrix and concentrations [5,12 and 19]. Thereby it is

logical to see that the reduction potential of a given metal

ion in BOAE samples to be hgigher than in that of

BOBE. Besides the potential, it is clearly indicated from

the voltammograms that the peak currents of Pb and Cd

in Borkena River after the effluent join the river are

higher than that of BOBE samples. Based on the peak

currents of oxidation, concentrations of each metal in

BOBE and BOAE samples were determined to be 21.7 ±

2 and 333.5 ±4 μg /L for Pb and 3.95 ± 1 and 231.5 ± 4

μg /L for Cd in the respective order.

3.4 Tap water Sample

The tap water sample was also collected from

Bhirdar University for examine the heavy metal. The

study is shown in Fig.12.

Fig. 12: Differential pulse anodic stripping voltammogram for Pb

and Cd in sample of BDU tap water ; a) peak of Pb and b) peak of

Cd.

The sensitivity for Pb and Cd determined by standard

addition method were found to be 21.7 nAL/μg and

202.4 nAL/μg, respectively. The calculated

concentrations for each metal were 21.7 ± 0.5 μg /L for

Pb and 4.1 ± 0.2 μg /L for Cd. The net currents of Pb and

Cd found in the sample were 0.5 μA and 0.83 μA

respectively. The concentration of Pb is greater than that

of Cd unlike their peak current values. This is due to the

sensitivity of the technique, that is, the magnitude of the

current produced per 1 μg/L of each metal was lower for

Pb than for Cd and hence the ratio of the peak current to

the sensitivity (concentration) was greater for Pb.

3.5 Comparatively Study

Eighteen different samples were analyzed by

differential pulse anodic stripping voltammetry. Seven

waste effluent samples from three industries, ten river

water samples, and one tap water sample were probed for

Pb and Cd. The mean Pb and Cd contents of all samples

were successfully determined. Both metal ions were

found in KOSPI waste sample, in Borkena River water

samples collected at two sites, before and after the

effluents mix with the river and in tap water sample of

Bihar Dar University. Only Pb was found in BGI and

textile samples. The results of the experiments are

summarized in Table 2.

Table 2: Concentration of heavy metal in different sample and limits

S.No

Type

Sample

Pb (



g/L)

Cd(



g/L)

Effluents

Textile

134±3

Not dected

BGI

241±5

Not dected

KOSPI

514.4±4

251±5

River Water

BOBE

21.7

3.95

BOAE

333.5

230.5

Drinking Water

Tap Water

4.1

Permissible Limits

WHO (Drinking)

FAO (Irrigation)

500

100

It is evident from the results that the concentrations

of each toxic metal ion vary significantly in different

drains depending on the nature of waste effluents. As it

can be seen from Table 2 the highest concentration of

both toxic metals, Pb and Cd, were released from

KOSPI. Only Pb was found in BGI and Textile waste

effluents. The least polluted effluent both in quality and

quantity discharges out from textile.

The Borkena river water samples which were

collected at two sites, (before and after industrial drain

system joins the river) showed substantial difference in

their Pb and Cd content. The concentrations of each

metal ion in the river at the site just after the junction

point of the drain system were found much higher than

the other site.

It is apparent from the result that huge amount of

toxic metal ions are released from various industrial

drains at Kombolcha to Borkena River. The

concentrations of metal ions determined in three

industrial effluents are graphically compared in Fig. 13.

Fig.13: Comparatively study of heavy metal different industry

The sources of chemical contaminants of

environmental matrixes occur when chemicals are used

in industries and disposed with wastes. Agricultural

-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3

0.0004

0.0006

0.0008

0.0010

0.0012

0.0014

0.0016

0.0018

0.0020

0.0022

Current (mA)

Potential (V) vs. Ag/AgCl

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 118-125

124

activities, such as use of excessive amount of fertilizers,

pesticide and contaminated water for irrigation causes

contamination of crops. Thus the Pb and Cd

contamination of BOAE by industrial wastes at

Kombolcha should come from their applicability in the

nearby industries. Generally it is recognized that;

cadmium is used in metal plating, coating, pigments

stabilizer, and painting. Lead is used in painting dying,

and welding activities. Thereby the possible sources of

the contaminant Pb and Cd in KOSPI are wastes from

painting, plating, stabilizing and welding activities of the

steel products. In textile wastes from the use of dyes for

textile products is the most supposed source. For BGI,

the by-product of brewing crops, which have been

harvested by application of fertilizers, pesticide and use

of contaminated irrigation water, is the suspected source.

Trace metals can be absorbed by roots of plants and can

exist in adsorbed or complex forms with organic

compound. As toxic level of Pb and Cd in drinking water

or food results in profound disturbance to the normal

biochemical and neurological process by crossing the cell

membrane, the Borkena River water just as it reaches

Kombolcha is dangerous to people and to any aquatic life

[22-25].

4 Conclusions

The investigation of the contamination potential of

industrial wastes on Borkena River was successfully

accomplished in differential pulse anodic stripping

Voltammetry on glassy carbon electrode. Based on the

findings, Borkena River water gets polluted highly due to

toxic metals Pb and Cd when it reaches Kombolcha. The

quality of the river water is not safe for domestic use.

The largest contributor of the pollutants Pb and Cd was

Kombolcha steel products industry. Kombolcha brewery

and Kombolcha textile factory was the second and third

in their lead content, however, there are other factories

which were not included in this work and may cause

pollution. Such unregulated discharge of toxic metal

containing waste effluents should be ceased to avoid

farther pollution. Furthermore, the current effect of the

contamination of Borkena River on human and aquatic

life should be subject to full investigation. Finally this

work is not complete and exhausted. But, it lights

awareness and can be used as a foot step for full

investigation of environmental pollution.

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