Proceedings of International Conference on Planning, Architecture and Civil Engineering, 07 - 09 February 2019,

Rajshahi University of Engineering & Technology, Rajshahi, Bangladesh

Assessment of Tannery Effluent: A Case Study on Dhaleshwari River

in Bangladesh

P. K. GHOSH1 & M. D. HOSSAIN2

1
Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh, <
premkumerghosh@gmail.com >
2
Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh, <
delwar@ce.buet.ac.bd >

Abstract

Effluents from leather processing industry which already crippled Buriganga river in Bangladesh and now
destroying Dhaleshwari water as well. It is one of the main source of continuous input of pollutants in river water
which hampers the aquatic ecosystem. In this study we made an investigation on the effect of tannery effluents on
Dhaleshwari river water near Savar, Dhaka. As the river water continuously polluted by tannery effluents so
concentration of tannery effluents in river water is getting high day by day. So, the CETP’s effluents and influents
were mixed with Dhaleshwari water at concentration of 5%, 25%, 50%, 75%, 90% and analyzed along with the
river water, effluent and influent of CETP. Then physicochemical properties like pH, Conductivity, Total
Dissolved Solid(TDS), Total Alkalinity(TA), Total Hardness(TH), Dissolved Oxygen(DO), Biological Oxygen
Demand(BOD), Chemical Oxygen Demand(COD), Sulfate , Chloride and Chromium are analyzed for all the
samples and the results show that with the increasing effluent concentration water quality getting worse day by
day. If this continues, will pose a serious threat to aquatic ecosystem, agriculture and human life. We also found
an idea about the efficiency of the CETP by assessing both CETP’s influents and effluents.

Keywords: Tannery effluents; River water; Concentration; Physicochemical.

1 Introduction

Leather industry plays an important role in Bangladesh Economy due to its large potential for employment, growth
and export (Tinni et al, 2014). At the same time, it poses serious environmental threats by discharging liquid
effluents and solid wastes directly into surrounding low lying areas (Tinni et al, 2014). Savar is a major industrial
area of Dhaka city and now a major part of Leather industry of our country relocated there. The CEPT in Savar
has the capacity to treat, if properly functional, 2500 cubic meters of waste, but the tannery industries produce
more than double that during this large religious festival (Lynne, 2018). Finally, not all the tanneries go through
the CETP .That’s why we selected Dhaleshwari River near Savar, Dhaka. Physicochemical and microbiological
characteristics may describe the quality of water, therefore an analysis of physicochemical parameters of River
water was made by many workers (Sinha, 1986; Trivedi et al, 2009; Sinha et al, 2000; Richa et al, 2012; Vinod et
al, 2003; Yadav et al, 2011). Industrial effluents from leather tanneries discharged higher amount of metal
especially chromium (Vinay et al, 2014). These effluents released on river or canal as well as dump into ground
water and lead to contamination of chromium due to accumulation (Vinay et al, 2014). Tanneries caused
environmental problem very much. Survey results showed that the most environmental effect was bad smell to the
surrounding area, indicated by respondents of 45% and the secondly scarcity of fresh water was 32% among the
respondents (Tinni et al, 2014). The waste water were fall in the nearby river and the slums people use these water
which causes various diseases to them. Over 8,000 workers in the tanneries suffer from gastrointestinal,
dermatological, and other diseases, and 90% of this population dies before the age of 50 (Human Rights Watch,
2012). Major problems are due to waste water containing heavy metals, toxic chemicals, chlorides, lime with high
dissolved and suspended salts and other pollutants (Uberai, 2003). Tanneries generate waste water in the range of
30-35 L/Kg skin/hide processed with variable pH and high concentration of suspended solids, BOD, COD, tannins
including chromium (Nandy et al, 1999). The present work is focused to see the modulatory effect of tannery
effluents on physicochemical parameters like pH, temperature, conductivity, TH, TA, TDS, DO, COD, BOD, SO4,
Cr etc. of Dhaleshwari River water. The Water quality of Dhaleshwari River can be estimated after addition of %
tannery effluents in laboratory condition to predict the future status of river water (Vinay et al, 2014). This is why

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we run this study. The observed values of various physicochemical parameters of water samples were compared
with standard values recommended by world health organization (W.H.O, 1993).

2 METHODOLOGY

Water sample was collected from Dhaleshwari River 3km upstream from tannery village and treated and untreated
tannery effluents was collected from Common Effluent Treatment Plant (CETPs) Savar, Dhaka. At 1st we collected
the river water, tannery influent and effluent from CETP in the month of November and run the study. Then we
also collected the river water in the month of June and run the test with influent and effluent collected from
(CETPs)Savar, Dhaka. That’s how we also get a seasonal variation of the river water. The percent of effluents viz.
5%, 25%, 50%, 75%, 90% v/v were made in the collected river water sample and these concentrations were used
for physicochemical analysis.
The samples were kept in room temperature. The pH of samples (river water, 5%, 25%, 50%, 75%, 90% effluent,
100% effluent) was determined using a digital pH meter. Conductivity of samples was determined using EC meter.
Temperature and Dissolve Oxygen (DO) were determined by digital DO meter. TDS was determined by standard
method. Total Hardness (TH), Total Alkalinity (TA) were determined by titration. 5 days incubation method was
used to test BOD and Chemical Oxygen Demand (C.O.D.) was measured by open reflux method. Sulphate and
Chloride were determined by direct Spectrophotometric method. Trace metal Cr was determined by digesting the
sample with concentrated HNO2 and H2SO4 made up to 50 ml volume and analyzed by atomic absorption
spectrometer.

3 RESULTS AND DISCUSSIONS

The observed average values of the samples water quality parameters of the study are given in Table 1 & 2 for
different percentage concentration of effluents and influents. The effluents were collected in the month of
November (winter season) 2017 and influents were collected in the month of June respectively.
The Dhaleshwari river water quality is seriously affected by tannery waste. The observed average value of the
Dhaleshwari river water quality parameters of the present study are given in table 1 for different percentage
concentration of effluents. The treated effluent was rich in TDS, deficit in DO, high BOD and COD. The pH value
ranging from 7.4 to 8.5 is an essential factor in formation of algal blooms (Palharyal et al, 1993). Low or high pH
value makes the water unfit for irrigation and soil becomes alkaline resulting in poor crop growth and yield (Vinay
et al, 2014). The observed value of pH for River water sample is 7.8 in winter and 7.4 in wet season, shows that
Dhaleshwari water sample is alkaline in nature. Almost alkaline nature remains for different percentage dilution
of Dhaleshwari water sample, not exceeding the pH value 8.5 with both tannery effluents and influents. The pH
was found slightly alkaline for sample of tannery waste water. Other workers also reported alkaline tannery waste
water (Deepali et al, 2009; Kadam et al, 1990). The EC of Dhaleshwari water sample was found 0.65 mS/cm in
winter and 0.35mS/cm in wet season. For different percentage of sample with tannery effluent, EC was found in
increasing order for both tannery effluents and influents. The EC were found from 1.16 mS/cm to 12.4 mS/cm for
5% to 100% tannery effluents modulated sample and 1.56 mS/cm to 13.33mS/cm for 5% to 100% tannery influents
modulated sample. Increase in EC values indicates the presence of higher concentration of ions (Vinay et al, 2014).
Furthermore, TA of River water was found 113 mg/L in winter and 238 mg/L in wet season. TA was found 286
mg/L to 1732 mg/L for different effluents percentage concentration of water samples from 5% to 100%, while TA
was found 178 to 2028 mg/L for 5% to 100% influent modulation for water sample. 260 mg/L is even beyond the
highest desirable limit prescribed by WHO standard for drinking water.

Table 1. Effect of different concentration of tannery effluent on physicochemical properties of the Dhaleshwari
River water.

Parameters Units River Water 5% 25% 50% 75% 90% Influent

Temperature ◦C 23 23 23 23 23 23 23
pH 7.8 8 8.2 8.3 8.3 8.4 8.5
Conductivity mS/cm 0.65 1.16 3.64 6.62 9.46 11.35 12.4
TDS mg/L 400 690 2090 3850 5560 6740 7410
TA mg/L 238 286 565 894 1246 1494 1732
TH mg/L 204 216 320 370 430 490 510

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DO mg/L 3.99 1.22 0.05 0.04 0.04 0.03 0.03

COD mg/L 12 23 235 587 779 1002 1228
BOD mg/L 4.8 20.8 50.4 82.4 102.4 160 240
Sulphate mg/L 60 130 450 925 1025 1400 1850
Chloride mg/L 40 160 1100 1900 2900 3700 3800
Chromium mg/L 0.014 0.267 1.837 3.779 6.132 7.569 8.197

Table 2. Effect of different concentration of tannery influents on physicochemical properties of the Dhaleshwari
River water.

Parameters Units River Water 5% 25% 50% 75% 90% Influent

Temperature ◦C 29.5 29.5 29.5 29.5 29.5 29.5 29.5
pH 7.4 7.8 8.2 8.4 8.4 8.4 8.5
Conductivity mS/cm 0.35 1.56 3.88 7.55 10.02 12.25 13.33
TDS mg/L 270 780 3037 4630 6810 8245 9280
TA mg/L 113 178 602 963 1454 1613 2028
TH mg/L 179 213 343 412 507 578 602
DO mg/L 4.41 1.8 0.11 0.04 0.04 0.03 0.02
COD mg/L 9 24 347 713 967 1403 2314
BOD mg/L 2.8 43 132 203 390 476 730
Sulphate mg/L 18 200 525 1050 1200 1550 1900
Chloride mg/L 24 120 1300 2400 3400 4300 4500
Chromium mg/L 0.01 3.013 28.267 57.014 113.569 133.029 147.257

The value of total hardness (TH) of River water was found 204 mg/L in winter and 179 in wet season. TH was
found 216 mg/L to 510 mg/L for different effluents percentage concentration of water samples from 5% to 100%,
while TH was found 213 to 602 mg/L for 5% to 100% influent modulation for water sample. 180 mg/L is the
highest desirable limit prescribed by WHO standard for drinking water.TA was found 286 mg/L to 1732 mg/L for
different effluents percentage concentration of water samples from 5% to 100%, while TA was found 178 to 2028
mg/L for 5% to 100% influent modulation for water sample. 260 mg/L is even beyond the highest desirable limit
prescribed by WHO standard for drinking water. The presence of calcium, magnesium and bicarbonates in excess
makes water unfit for irrigation since its application increase problem of soil salinity and its permeability
detrimental to crop plants (Srinivas, 1984) .
For different percentage of sample with tannery waste water, TDS was found in increasing order for both tannery
effluents and influents. The TDS were found from 690 mg/L to 7410 mg/L for 5% to 100% tannery effluents
modulated sample and 780 mg/L to 9280 mg/L for 5% to 100% tannery influents modulated sample. In winter the
river water’s TDS was 400 mg/L and 270 mg/L in wet season.
Dissolve Oxygen (DO), is an important factor for water (Vinay et al, 2014). Here we can see that for both the
influents and effluents the value of DO is very low. For the river water we found DO value 3.99 mg/L in winter
and 4.41 in wet season which are also very low.
For different percentage of sample with tannery waste water, COD value was found in increasing order for both
tannery effluents and influents. The COD were found from 23 mg/L to 1228 mg/L for 5% to 100% tannery effluents
modulated sample and 24 mg/L to 2314 mg/L for 5% to 100% tannery influents modulated sample. In winter the
river water’s COD was 12 mg/L and 9 mg/L in wet season. High COD and BOD value indicate the pollution
strength of the waste water (Vinay et al, 2014).
For different percentage of sample with tannery waste water, BOD was also found in increasing order for both
tannery effluents and influents. The BOD values were found from 20.8 mg/L to 40 mg/L for 5% to 100% tannery
effluents modulated sample and 43 mg/L to 730 mg/L for 5% to 100% tannery influents modulated sample. In
winter the river water’s BOD was 4.8 mg/L and 2.8 mg/L in wet season.
Sulfate was found in increasing order for both tannery effluents and influents with increasing effluent percentage.
We found Sulfate from 130 mg/L to 1850 mg/L for 5% to 100% tannery effluents modulated sample and 200 mg/L
to 1900 mg/L for 5% to 100% tannery influents modulated sample. In winter the river water’s Sulfate was 60 mg/L
and 18 mg/L in wet season. The WHO limit for Sulfate in drinking water is 630 mg/L (WHO).

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Figure 1. Effect of tannery effluents on physicochemical properties of the Dhaleshwari River water.

Chloride amount in samples also increased with the increasing concentration of tannery waste water. The Chloride
were found from 160 mg/L to 3800 mg/L for 5% to 100% tannery effluents modulated sample and 120 mg/L to
4500 mg/L for 5% to 100% tannery influents modulated sample. In winter the river water’s Chloride was 40 mg/L
and 24 mg/L in wet season. Chromium and its compounds are toxic, which are being mixed with natural water
from a variety of industrial effluents (Siraj et al, 2012). Tannery is a major source of Chromium as waste in water.
It leads to liver damage, pulmonary congestion and causes skin irritation as well as results in ulcer formation (Raji,
1998). In winter we found 0.014 mg/L Chromium and in wet season 0.01 mg/L Chromium in Dhaleshwari river

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water. The Chromium were found from 0.267 mg/L to 8.197 mg/L for 5% to 100% tannery effluents modulated
sample and 3.013 mg/L to 147.257 mg/L for 5% to 100% tannery influents modulated sample which is higher than
WHO permissible limit for Chromium in drinking water.

4 CONCLUSIONS

From the study we can see that the water quality of Dhaleshwari River is getting damaged at a great extent. After
adding only 25% tannery effluent all the WHO limits were crossed. As mixing of tannery effluent is a continuous
process, then that day is not so far when Dhaleshwari will turn into new Buriganga. The CETP isn’t working at
that limit as it need to be. So continuous and periodical monitoring of water quality is necessary so that appropriate
preventive measures can be undertaken. Other than that serious environmental quality deterioration could take
place in a few years which will be serious threat for human and aquatic life. We also get the idea that water quality
is varies with temperature and seasons. The situation will be even more catastrophic if the effluents are directly
discharged into the river without using the CETP. So all the tanneries in Savar should discharge their waste water
at first into the CETP and for that necessary steps should be taken as soon as possible. Other than that the situation
will be horrible.

5 ACKNOWLEDGEMENT

The authors would like to acknowledge Department of Civil Engineering for the lab facilities, the lab assistants of
Environment lab, BUET for their help. Also like to acknowledge stuff of CETPs for their help.

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