CE 6305
Water pollution and its control
Term paper
On
WATER POLLUTION AND ITS CONTROL STRATEGIES IN KHULNA CITY
PERSPECTIVE
Submitted To
Khondoker Mahbub Hassan
Professor
Department of Civil Engineering
Submitted By
Name: Md.Tahasin Khan
Roll No: 1901560
Department of Civil Engineering
Khulna University of Engineering & Technology
Khulna-9203, Bangladesh
Abstract
Khulna is the third largest city of Bangladesh and situated at the Southwest region of the country
having 1.4 million populations living in 45.65 square kilometers area. It has been facing growing
urban environmental problems due to daily generated wastewater. There is no sewerage network
or any central treatment system in Khulna city. Conventional wastewater treatment plant needs
large space for treating vast quantities of wastewater and also requires very high initial as well as
operation and maintenance cost. This study is concerned about the two decentralized wastewater
treatment (DEWAT) plants constructed at the Peoples Panchtola Colony' at Khalishpur in Khulna.
DEWAT system may be defined as the collection treatment, and disposal or reuse of wastewater
from individual homes, clusters of homes, isolated communities, industries or industrial facilities
at or near the point of waste generation. The specific objectives of this study were to study the
performance of two DEWAT plants regarding its technical and socio-economic acceptance by
ordinary population in Panchtola Colony, compare the performance of two DEWAT plants based
on field and laboratory investigations. To conduct necessary investigation both in field and
laboratory, wastewater samples were collected from six different points. The experimental results
when wastewater passed through ABR, achieved removal efficiency are 65%, 64%, 93%, 44%,
32%, 48%, and 50% for BOD5, COD, TSS, TDS, FC, Nitrate and Phosphate respectively in the
DEWAT plant . The results show that the concentration of all harmful parameters were reduced
significantly and lowered to an acceptable level. The results also indicate the effectiveness of
ABR and AFBBR over the planted gravel filter considering the area required for PGF.
Introduction
Due to unaffordable cost of construction, most of the drains in the towns and cities are open and
as a result they are misused, sometimes serving as defecating sites for homes without adequate
toilet facility(Arifurrahman et al., 2013).Sewage water management is one of the major
environmental issues of recent times. Waste is produced by all human being, but the amount is
very large for humans. So it is our responsibility to manage it efficiently. Due to rapid urbanization,
industrialization and massive growth of population waste management has become more critical
nowadays. Normally if the quantity of waste water is small, nature can cope with it but if large
amount of wastewater and sewage are not treated then nature can’t endure it. Normally sewers are
discharged into lake, river, and stream. But now in developed countries it is not directly discharged
into it. At first the water is treated then it is discharged. In most of the case in Bangladesh though
there is soak well in office building, there is hardly any septic tank in residential or private building.
Though the population is increasing in an alarming rate the area is same. In major cities of
Bangladesh the buildings are congested so there is not enough area for the treatment process. So
the management process should be done carefully keeping in mind of the little space. Waste
produced by residential buildings should be treated before discharging to the environment. Sewage
is of two kinds one is black water, which is from toilet and the other is gray water, which is from
domestic uses except toilets. Bangladesh provides a striking example of progress to meet the
Millennium Development Goal (MDG) - 7 to halve, by 2015, the “proportion of urban population
with access to improved sanitation”. Open defecation has reduced from 19% in 2000 to 3% in
2012, though 53% of households still do not use improved sanitation (WHO-UNICEF, 2014).
Blockage of drainage systems occurred for wastewater overflow during rainy season. In
consequence, self-purification capacity of receiving water bodies is overloaded and it causes
surface and ground water pollution, impacting directly to the health of community, reducing the
value of environment(Systems, 2002). Progress in reducing open defecation and use of improved
sanitation in Bangladesh has been remarkable. Only 4% of the population are practicing open
defecation, 15% of the population are using unimproved latrines, 25% of the population are sharing
improved latrines and 56% of the population are using improved latrines (WHO-UNICEF, 2014).
According to JMP, open defecation reduced from 34% in 1990 to 3% in 2012 and now it said to
be of 1% (WHO-UNICEF, 2014).Conventional wastewater treatment plant needs large space for
treating vast quantities of wastewater and also requires very high initial as well as operation and
maintenance cost that Khulna municipality faces structural and financial adjustment problems
(Shuma rani saha, 2014). Sewage/Wastewater treatment involves breakdown of complex organic
compounds in the wastewater into simpler compounds that are stable and nuisance-free, either
physio-chemically and or by using micro-organisms (Cheremisinoff, n.d.). Methods of wastewater
treatment were first developed in response to the adverse conditions caused by the discharge of
wastewater to the environment and the concern for public health. Further, as cities became larger;
limited land was available for wastewater treatment and disposal, principally by irrigation and
intermittent filtration. Also, as populations grew, the quantity of wastewater generated rose rapidly
and the deteriorating quality of this huge amount of wastewater exceeded the self-purification
capacity of the streams and river bodies(Spellman, 2010).
Khulna is the third largest city of Bangladesh located in the south-western part of the country and
lies in the delta of the river Ganges. The city has an estimated population of 1.6 million and total
number of household is 66,257 (SNV, 2014). Human deposits about 70 g per capita per day of
solids into water and also produce more and more waste water daily. Direct or indirect contact to
wastewater and fecal sludge is associated with microbial and chemical hazards, which frequently
result in adverse effect both on humans and animals. Khulna City Corporation (KCC) is adversely
affected by the influence of sewage water. This city has no sewer network. The household
sanitation is predominantly on-site technologies, 68.4% septic tanks and 31.6% pits(Foundation,
2011), which require regular emptying. But formal emptying is rare as most are directly connected
to surface water drains or water bodies. In many developed countries, fecal sludge is often allowed
to accumulate in poorly designed plant whereas this scenario is not very common in the developing
countries. Without proper management, fecal sludge is often allowed to accumulate in poorly
designed pits and wastewater is discharged into storm drains and open water, or is dumped into
waterways, wasteland, and unsanitary dumping sites (Water and Sanitation Program, 2014).The
major obstacle on the way to successful implementation of any sewage treatment process in middle
and low income countries are the stake holders. In Khulna as well as Bangladesh, the key
stakeholders are household’s users and owners, municipal authority, pit or septic tank emptier or
sweepers, government, local or international organizations and NGOs with sanitation activities.
Adequate water and wastewater management, essential for human health and economic
Development, poses a major challenge to many countries around the globe. Whereas in
Industrialized countries water and wastewater control had reached a fairly high Standard, in lower
and middle income countries1 severe problems with respect to water Supply and wastewater
management are still apparent (Hophmayer-Tokich, 2006). As the water supply system is given
the first priority, waste water treatment is lagging behind and is becoming a major issue in different
cities in a developing country like Bangladesh. The main aim of this paper is to investigate the
existing treatment systems, assessment of raw sewage and effluent sewage quality through
different treatment systems in small space.
Materials and Methods
Performance study of existing two DEWAT plant and its modification
Baseline survey
Questionnaire for
DEWAT users
Questionnaire for
non DEWAT users
Analysis of field data
Evaluation of
socioeconomic
acceptance of
DEWAT plant
Identification of
technical problems
in O & M
Collection of wastewater samples
Laboratory determination of
wastewater quality parameters
Analysis of test results
Comparison of performance of
existing two DEWAT plants
Providing recommendations for necessary modifications
of DEWATS for its sustainable development
Fig 1: Flowchart showing the sequential steps in the research works
Selection of study area
After the independence in 1971 there was no reformation of the pipes that were used in khalishpur
area. Among all the wards in Khulna, The wards under khalishpur have the worst sanitation system.
The sewerage system is directly connected to the drain which is very harmful. Most of the
residential building don’t have any soak pit. That’s why the BOD and fecal coliform limit for
wastewater crosses the allowable limit and causes different diseases to different people. Here
sewage and waste from residential buildings are dumped beside their residence as there is hardly
any sewerage systems or dumping place for management. That’s why the area under ward no.10
was selected to be surveyed.
Fig 2: Khulna City Corporation wards
Two DEWAT plants have been already constructed in Panchtola Colony at Khalishpur in Khulna
by a local NGO named as Nabolok. A field survey was carried out to investigate the performance
of the existing DEWAT plants. A sample of 166 families who are users of DEWAT plants was
selected. Family interviews were conducted in the families of the colony. This was done with
assistance of a Nabolok staff One questionnaire was prepared for the users of DEWAT plants
considering much information such as general, socio-economic, environmental condition, hygiene
practice, benefits of DEWAT plant, maintenance of DEWAT plants, and aesthetic view of
DEWAT plant, and recommendation on existing DEWAT plants. The aim of this survey was to
find out the socio-economic acceptance and technical problems of existing DEWAT plant
Fig 3: DEWATS system
A total of 1 liter sample was collected in 6 bottles from six different points such as inlet and outlet
of settler tank, middle of AFBBR, outlet of ABR, PGF and PP of two existing DEWAT plants of
the Panchtola Colony. Wastewater samples were collected from the DEWAT plants once a month.
Then the sample bottles were put in a cool box with ice cubes before being transported to the
environment laboratory at KUET campus. This was to prevent any change of wastewater quality
which could occur between the time of collection and analysis in the laboratory. Some parameters
which were determined immediately upon arrival in the laboratory included Faecal Coliform, DO
and BOD5.
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Results and Discussion
To get a broad view of community acceptance and management of the system, interviews were
carried out with key stakeholders. The interviewees were local people, relevant stakeholders and
authorities. This work gave few answers and evidences. Total 166 families were using the DEWAT
plants. During the field inspection, the users were asked only how much money they spent when
they had been suffering from diarrhea, cholera, hookworms etc. before implementation of DEWAT
plants.In this study, six sampling points of the two DEWAT plants and eleven experimental
parameters were selected as stated by Nabolok with the assistance of Water Aid Bangladesh. Those
points are in and outlet of settler tank, middle of anaerobic filter bed baffled reactor, outlet of
anaerobic baffled reactor, planted gravel filter and polishing pond.
It is observed from the result that when wastewater passed through ABR, achieved removal
efficiency are 65%, 64%, 93%, 44%, 32%, 48%, and 50% for BOD5, COD, TSS, TDS, FC, Nitrate
and Phosphate respectively in the DEWAT plant. Removal efficiency only planted gravel filter
are 61%, 37%, 38%, 12%, 29%, 38%, and 29% concentration based removal efficiency for BOD5,
COD, TSS, TDS, FC, Nitrate and Phosphate respectively. Removal efficiency only polishing pond
are 28%, 37%, 45%, 11%, 39%, 34%, and 38% for BOD5, COD, TSS, TDS, FC, Nitrate and
Phosphate respectively. Moreover, the total construction cost of DEWAT plant was BDT 900000,
whereas the construction cost of planted gravel filter was BDT 343112 (Table 4.9). It is observed
from the result (Table 4.8) that when wastewater passed through ABR, the 2' DEWAT plant
achieved 58%, 38%, 93%, 38%, 29%, 53%, and 37% for BOD5, COD, TSS, TDS, FC, Nitrate and
Phosphate respectively. Removal efficiency only planted gravel filter are 58%, 21%, 26%, 13%,
24%, 38%, and 28% concentration based removal efficiency for BOD5, COD, TSS, TDS, FC,
Nitrate and Phosphate respectively. Removal efficiency only polishing pond are 34%, 38%, 58%,
18%, 28%, 60%, and 23% for BOD5, COD, TSS, TDS, FC, Nitrate and Phosphate respectively.
Moreover, the total construction cost of 2 DEWAT plant was BDT 1500000, whereas the
construction cost of planted gravel filter was BDT 834762
Table 1: Comparison of the 1st and 2nd DEWAT plants
Parameters
Mean removal efficiency, (%)
1st DEWAT plant
Mean removal efficiency, (%)
2nd DEWAT plant
BOD5
88.58
83.37
COD
77.12
58.12
TSS
92.26
96.22
TDS
39.87
19.3
FC
65.86
17.66
Nitrate
52.75
68.73
Phosphate
52.91
37.28
Conclusions
This research investigated the performance of Decentralized Wastewater Treatment Plants in
Khulna. The study had four major objectives: (a) to study the performance of two DEWAT plants
regarding its technical and socio-economic acceptance by ordinary population in Panchtola Colony
in Khulna, Bangladesh; (b) to compare the performance of two DEWAT plants based on field and
laboratory investigations
Concerning the first objective of this thesis, the performance of DEWAT plants regarding its
technical and socio-economic acceptance by ordinary residents in Panchtola Colony in Khulna,
Bangladesh is highly appreciated in response to colony residents who are using the DEWAT plant
.With reference to second objectives of this paper, from the performance study of two DEWAT
plants it can be seen that the removal rate was higher in the 1st DEWAT plant compared to the 2nd
DEWAT plant.
According to economic point of view, DEWAT plants were impended as a source of water supply
for irrigation purposes. It was found that treated wastewater comes from polishing can be reused
for irrigation purposes or reused for the community toilet flushing. DEWAT plants can be reduced
the withdrawal of fresh water from ground water. DEWAT plants not only save fresh water but
also save withdrawal cost such as power cost. DEWAT plants were also profitable through
reduction of medical cost and loss of income due to illness which is another positive attitude of
this technology.
Finally, it can be concluded that the modified DEWAT system should be practiced in low incoming
developing countries as a mid-term solution to improve the sanitation condition.
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Khulna City, 13(8), 978–984.
Cheremisinoff, N. P. (n.d.). HANDBOOK OF WATER AND WASTEWATER TREATMENT
TECHNOLOGIES.
Foundation, M. G. (2011). Landscape Analysis and Business Model Assessment in Faecal Sludge
Management : Extraction and Transportation Models in Bangladesh Final report –
Bangladesh 20 October 2011, (October), 1–67.
Hophmayer-Tokich, S. (2006). Wastewater Management Strategy: centralized versus
decentralized technologies for small communities. CSTM-Reeks, 271(271), 27. Retrieved
from
https://research.utwente.nl/en/publications/wastewater-management-strategycentralized-v-decentralized-techno
Shuma rani saha. (2014). Study on the Decentralized Wastewater Treatment Plants in Khulna $.
Spellman, F. R. (2010). Spellman’s standard handbook for wastewater operators. CRC Press (Vol.
II). https://doi.org/10.1201/EBK1439818862
Systems, W. T. (2002). Decentralized wastewater treatment - new concept and technologies for
Vietnamese conditions. Science And Technology, (September), 24–26.