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An Internship Report on Chittagong Water Supply and Sewerage Authority (CWASA) Submitted by- Quock San MS Environmental Science ID: 08208067 Session: 2011-12 Institute of Forestry and Environmental Sciences, University of Chittagong (IFESCU) Date: 10 th March 2014
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Page 1: An Internship Report on Chittagong WASA

An Internship Report on

Chittagong Water Supply and Sewerage

Authority (CWASA)

Submitted by-

Quock San

MS Environmental Science

ID: 08208067

Session: 2011-12

Institute of Forestry and Environmental Sciences,

University of Chittagong (IFESCU)

Date: 10th March 2014

Page 2: An Internship Report on Chittagong WASA

I

ACKNOWLEDGEMENT

At first, I express my profound gratitude to the God, the gracious and most munificent, who gives me

the energy and sound health to endure the rigor of this job.

We would like to express our profound sense of gratitude to Dr. Tapan Kumar Nath, Professor and

Acting Director, Institute of Forestry and Environmental Sciences, University of Chittagong

(IFESCU), provided us an opportunity to do our internship at Chittagong Water Supply and

Sewerage Authority (CWASA).

Utmost gratitude to The Chief Engineer Md. Abdul Karim Chowdhury of CWASA who accepted us as

an internee at their company and provided us an opportunity to enrich our technical competence as

well as increasing our managerial skillfulness regarding environmental aspects.

Then we would like express our sincerest gratitude to Secretary Md. Samsudduha, and Deputy-

Secretary Jahangir Alam Chowdhury, CWASA for their pleasant and benevolent cooperation.

We owe an immense debt of gratitude to Mr. Milan Kumar Chakraborty, Senior Chemist, Mohara

Water Treatment Plant (WTP), CWASA who helped us all the time by providing necessary

information whenever we need.

We want to express our sincere thanks to Executive Engineers of CWASA Md. Sarfaraj Akhter

(Mohara WTP), Md. Ariful Islam (MOD-2), Md. Mahbubul Alam (MOD-1), and Noor Mohammad

Abul Basher (Design Section) provided us a lot of information, suggestions and accompany us during

work under his supervision in their divisions.

We are thankful to Assistant Engineers of CWASA Mr. Sajib Barua (Mohara WTP), Mr. Soumit

Paul (Booster), Mr. S. M. Rabiul Hossain (MOD-2), Md. Abdur Rouf (MOD-1) for their kind

cooperation, assistance and providing important information in their divisions.

Then we would like to thank Sub-Assistant Engineer of CWASA Mr. Rafiqul Islam for his kind

support, assistance and accompany during our work in his divisions.

We are also indebted to all officials and staffs of CWASA for their cordial help and collaboration

during our work making life easier for us, which will be useful in our future career. We apologize if we

forgot to mention names of other personnel, but however, we are extremely grateful to every one

whatever he/she has offered us during our internship.

Author

10th March 2014

Page 3: An Internship Report on Chittagong WASA

II

TABLE OF CONTENTS

ACKNOWLEDGEMENT I

TABLE OF CONTENTS II

LIST OF TABLES IV

LIST OF FIGURES IV

LIST OF ABBREVIATIONS V

CHAPTER ONE: INTRODUCTION

1.1 General overview 1

1.2 Summary of Existing Facilities of CWASA 2

CHAPTER TWO: MOHARA WATER TREATMENT PLANT

2.1 General information 3

2.2 Halda River 3

2.3 Main Components of Mohara Water Treatment Plant 4

2.4 Treatment process description 4

2.5 Treatment plant design data 7

2.6 Description of Process Unit 8

2.6.1 Intake and Raw Water Pump Station 9

2.6.2 Desilting Basin 9

2.6.3 Rapid Mixture 10

2.6.4 Clarifiers 10

2.6.5 Filters 10

2.6.6 Clear Well and High Lift Pump Station 10

2.6.7 Chemical Facilities 10

2.6.8 Sludge and Backwash Facilities 11

2.6.9 Power Supply and Generator 11

Page 4: An Internship Report on Chittagong WASA

III

2.6.10 Laboratory 11

2.6.11 Plant Monitoring Arrangement 13

CHAPTER THREE: KALURGHAT IRP AND BOOSTER STATION

3.1 General information 15

3.2 Source and Treatment of Water in Kalurghat IRP 15

3.3 Treatment Procedure 16

3.4 Quality of Water 17

CHAPTER FOUR: MAINTENANCE, OPERATIONS AND DISTRIBUTION

(MOD)

4.1 General information 18

4.2 Coverage area: 18

4.3 Main activities: 18

CHAPTER FIVE: DESIGN DIVISION

5.1 Activities 19

CHAPTER SIX: CONCLUSION

6.1 Conclusion 21

Page 5: An Internship Report on Chittagong WASA

IV

LIST OF TABLES

Table 2.1: Daily Water Analysis of Mohara WTP 12

Table 2.2: Weekly Water Analysis of Mohara WTP 12

Table 2.3: Monthly Water Analysis of Mohara WTP 12

Table 2.4: Water Quality of Mohara Water Treatment Plant 13

Table 3.1: Quality of water before and after treatment in Kalurghat Iron Removal

Plant (IRP).

17

LIST OF FIGURES

Figure 2.1: Process Flow Schematic of Mohara WTP 6

Figure 3.1: A Flow Chart of Kalurghat Iron Removal Plant and Booster Station 16

Figure 5.1: The activities of design division of CWASA 20

Page 6: An Internship Report on Chittagong WASA

V

LIST OF ABBREVIATIONS

WASA Water Supply and Sewerage Authority

CWASA Chittagong Water Supply and Sewerage Authority

WTP Water Treatment Plant

Ctg Chittagong

KV Kilovolt

KVA Kilovolt Ampere

Km Kilometer

MGD Million gallons per day

NTU Nephelometric Turbidity Unit

MLD Million Liters Per day

imp gal Imperial gallon

sft Square feet

ft Foot

m Meter

mm Millimeter

gm Gram

I or L Liter

Mg/l Milligram/liter

kw Kilowatt

lbs Pounds

ml Million liters

d Day

gpd Gallons per day

gpm Gallons per minute

fph Feet per hour

mg Million gallons

mil Million

gal Gallon

kg Kilogram

hr Hour

hp Horse Power

IRP Iron Removal Plant

PC Personal Computer

LCD Lower Circuit Panel

MOD Maintenance, Operation and Distribution

WHO World Health Organization

DO Dissolve Oxygen

BOD Biological Oxygen Demand

COD Chemical Oxygen Demand

TDS Total Dissolve Solids

Coli. Coli form

BWDS Bangladesh Water Standards

Page 7: An Internship Report on Chittagong WASA

VI

PDB Power Development Board

MIS Management Information System

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CHAPTER ONE

INTRODUCTION

1.1 General overview

Chittagong is the second largest city of Bangladesh. A part from being the main centre of trade,

commerce and industrial activities is the life line of the economy for its sea port. Country's first

Export Processing Zone was established in this city. Over the last 3 decades, Chittagong has

grown at a great pace. This decade's remarkable phenomenon in the economy of the country is

unprecedented growth of garment industry in Chittagong. Development of industries has brought

rapid increase of population. Chittagong has witnessed major growth in population over the last

3 decades; mainly due to migration from the country-side. Since 1971, the population of the city

has grown from about 0.5 million to more than 3.0 million in 2007. The city area has also

expanded. The total area of Chittagong and sub-urban areas (including proposed Hathazari and

Sitakunda) is around 270 sq. km. This kind of growth presents tremendous challenges to the

utility authorities in providing utility services. Chittagong WASA, responsible for the water

supply of port city has taken up its all necessary steps to digitalize its overall operations. For easy

access of the respected consumers to the information and data regarding CWASA, an website

has been launched. Through this website a new dimension has been added in its communication

with the respected consumers. For better customer service, CWASA facilitated the consumers

with online billing system. For improved operations of CWASA, heartiest co-operation from the

respected consumers is highly expected. CWASA is striving hard to keep pace with the city

development.

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1.2 Summary of Existing Facilities of CWASA

Facility Quantity Capacity

Surface WTP 1 no. 90 MLD

Ground WTP 1 no. 68 MLD

Deep Wells 91 nos. 115 MLD

Pipeline 610km -

Reservoirs 14 46,142 ML

HL & Booster 4 & 3 -

Service Conn. 57,043 nos. -

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CHAPTER TWO

MOHARA WATER TREATMENT PLANT (WTP)

2.1 General information

The Mohara Water Treatment Plant is the part of the city of Chittagong Water Supply

and Sewerage Authority’s (CWASA).

Commissioning: Commissioned in December 1987.

Capacity: Its Capacity is 20 million gallon per day (MGD).

Source: River Halda at a point nearly half a mile upstream from its confluence with

the river Karnaphuli.

2.2 Halda River

Originates at the Badnatali Hill ranges in Ramgarh Upazila in the Ctg. Hill Tracts.

Flows through Fatickchari Upazila, Hathazari Upazila, Raozan Upazila and Kotwali

Thana, and falls into the Karnaphuli River.

81km long river has a very turbulent tributary.

The Dhurung River, which joins Purba Dahlai about 48.25 km downstream.

Navigable by big boats 25km into it (up to Nazirhat) and by small boats 16-24km

further (up to Narayanhat).

Halda is famous for breeding Pure Indian carp.

This is the only pure Indian carp breeding field of Bangladesh, perhaps in South Asia.

2.3 Main Components of Mohara Water Treatment Plant

Intake and Raw Water Pump Station

Desilting Basin

Rapid Mixer

Clarifier

Filter

Chlorine Contact Chamber and Clear Well

High Lift Pump Station

Chemical Facility

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Sludge and Backwash Facility

Power and Standby Generator

Laboratory

Plant Monitoring Arrangement

2.4 Treatment process description

The objectives of the Mohara water treatment plant are not only to provide safe water for

human consumption and appealing to consumers, but to bring the water quality within the

limit of the maximum allowable standards set by the World Health Organization (WHO).

The raw water for the Mohara Water Treatment Plant is taken from the Halda River. The

Halda River Water contains varying level of alkalinity (10-75 mg/l) and turbidity (15-350

NTU). These variations are a result of seasonal changes with the monsoon season causing the

higher turbidities, low alkalinities and high level of suspended solids. The overall treatment

process units include an intake structure with bar racks, pump station, raw water rising main,

desilting basins, rapid mixtures, clarifiers, filters, clear well, high-lift pump station, sludge

and backwash facilities, standby power generator, chemical building and facilities and

administration building. The intake structure and pump station are located on the west bank

of the Halda River. The intake structure contains five separate compartments, each with a

capacity of 45 ml/d (10 imp mgd). Hand raked bar screens is located in each compartment to

prevent the entry of coarse debris and floating material. Each compartment includes a pipe

that connects the intake structure to the raw water pump station. Provisions have been made

for five raw water pumps, but initially two duty pumps and one standby pump have been

provided. After the intake structures, the raw water are lifted by the raw water pumps to

either the desilting basins or directly to the rapid mix units. Two desilting basins are provided

to reduce heavy sediment loads to the clarifiers during the monsoon season, but may be

bypassed during the dry season. Provision is made to add alum to the water at the raw water

meter vault to aid in the settling of suspended solids in the desilting basin if necessary.

After desilting the next process steps are chemical injection, flash mixing and coagulation.

Mixing takes place in two upflow chambers in series by means of vertical turbine mixtures.

Chemicals added at this point include alum for coagulation, chlorine for aquatic growth

control and when necessary lime for pH adjustment. Chemically dosed water flows from the

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mixing chambers to a series of 24 upflow, inverted pyramid shaped, solid-contacts

clarification tanks. The hydraulic energy released at the bottom of the tank by the incoming

coagulated water results in a decreasing mixing action as the water rises up the diverging

tank and sludge blanket. Sludge is drawn off each clarifiers sludge blanket continuously by

fixed sludge conditioning or periodically by a draw off pipe for the sludge which settles to

the bottom and consolidates when the tank is taken out of service for cleaning.

Clarified water is separated from the sludge blanket and collected near the surface with

submerged orifice launders and flows by gravity to the filters. The filters are inflow splitting,

constant rate, variable head, self-backwashing, rapid unisized mono-media sand filters. The

filters operate until the rising water surface in the filter box reaches the maximum level at

which time the filter must be taken out of service and backwashed. Backwashing is

accomplished by stopping the inlet flow with a manually operated plug. Filtered water from

the operating filters flows back through the clogged filter to clean the media. The backwash

waste water flows over the central backwash water channel and out to waste.

Filtered water flows by gravity into the chlorine contact zone of the clear well, where

chlorine is added for disinfection. From the contact zone the water flows over a weir into the

clearwell. The weir ensures that filtered water has a 30- minute contact time after the addition

of chlorine and maintains a constant head available for filter backwashing. The clearwell is

divided into two halves to allow alternative cleaning.

The high lift pump station is next to the clearwell. Five (four duty one standby) constant-

speed, electric, vertical centrifugal pumps delivered the treated water to the Battali hill

reservoir.

Sludge comes from three sources: the desilting basins, the clarifiers and filter backwashing.

The sludge side streams will be returned to the Halda River downstream of the plant raw

water intake. Typically the river surface is low enough to allow silt, sludge and backwash

water to flow by gravity through a pipeline to discharge in the river. During times of

relatively high tides or river flooding, backed up water will close a check valve diverting

sludge and backwash water into the wet well of the sludge and backwash water pumping

facility, where they will be lifted enough to permit gravity flow to the river. Three duty pump

and one standby pump are provided at the sludge and backwash facility to handle the sludge

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and wash water from the clarifiers and the filters respectively. Silt and sludge is withdrawn

from the desilting basins by gravity when the river stage is low enough.

Figure 2.1: Process Flow Schematic of Mohara WTP

2.5 Treatment plant design data

Plant criteria for the Mohara Water Treatment Plant are listed as follows:

Design Data:

Capacity: 91 ml/day

Raw Water Pumps:

Number-duty/standby 2/1

Capacity-each 45/day (12.7 imp mgd)

FILTERS

(8)

ALUM

FLOW

METER

RAW WATER

PUMPS (3)

SLUDGE & BACK

WASH WATER

PUMPS (4)

CLEAR WELLHIGH LIFT

PUMPS (4)

FLOW

METER

LIME

Cl2

PROCESS FLOW SCHEMATIC

BYPASS

SLUDGE CHANNEL

SL

UD

GE

& B

AC

KW

AS

H C

HA

NN

EL

TO DISTRIBUTION

DESILTING

BASIN (2)

HALDA RIVER

INTAKE &

SCREEN

CLARIFIERS

(24)

Alum

Cl2Lime

RAPID MIX

CHAMBERS

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Power-each 110 kW (132 hp)

Desilting Basins:

Number 2

Overflow rate 0.18 mm/s (312imp gpd/sqft)

Detention time 120 minute

Flash Mixers:

Number 2

Detention time 10 s/chamber

Power-each 5.6 kW (7.5 hp)

Clarifiers:

Number 24

Type Upflow solids contact

Detention time 1.2 hours

Overflow rate 0.75 mm/s(1333imp gpd/sqft)

Minimum upflow velocity 0.75 mm/s (8.9 fph)

Filters:

Number 8

Area-each 22.3m2 (480 sq. ft.) each half 2.44m *9.1m (8 ft*30 ft)

Controls Influent-splitting Self-backwashing

Media type Unisized, mono media sand

Media size 0.85-1.2 mm

Media depth 1.22 m (4ft)

Loading 3.1 mm/s (3.8imp gpm/sq ft)

Backwash Rate 16.3 mm/s (20imp gpm /sq ft)

Clear well

Chlorine contact zone

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Volume 2.27 ml (500000 imp gal)

Detention time 30min at91 ml/d(20imp mgd)

Clearwell volume 11.4 ml (2.5 mil/imp gal)

Standby power generation:

Number 2

Type Diesel fuel

Size 1000 kW

High-lift Pumps:

Number-duty/standby 4/1

Capacity-each 22.5 ml/d (5imp mgd)

Power-each 350 kW (468 hp)

Sludge Backwash Facility Pumps:

Number-duty/standby 3/1

Capacity-each 645 L/S (2250 imp gpm)

Power-each 22.4KW (30 hp)

2.6 Description of Process Unit

2.6.1 Intake and Raw Water Pump Station

20 MGD with necessary provision & space for expansion up to 40 MGD.

Intake & Raw water pumping station constructed for 40 MGD capacity to meet future

requirement.

Since construction of Intake structure on the river bank is difficult & expensive.

2 Nos. duty & 3 Nos. Stand-by Raw Water Pumps of capacity 11 MGD & 132/160 KW

each.

2.6.2 Desilting Basin

Turbidity level varies from 20 NTU to 800NTU.

Provision for two desilting basins has been made.

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During monsoon river water first brought to the desilting basins. Turbidity reduced by

the settlement of mud, sludge etc.

In winter, water directly passes to the rapid mixing chamber through a by-pass system.

Desilting basins overflow rate 311gpd/sqft and detention time 120 minutes.

2.6.3 Rapid Mixture

Water from desilting basins/raw water pump station comes in the Rapid mix chamber.

Alum & lime is mixed with water.

Alum & lime are injected at the rapid mix chamber from the Chemical Building.

Two rapid mixtures of 7.5 hp each with detention time 10 second/chamber.

2.6.4 Clarifiers

24 Nos. hopper bottomed up-flow type clarifiers.

Water from rapid mix chamber come to the bottom of clarifier through 12" dia ductile

iron pipe from incoming channel.

Velocity of incoming water is reduced considerably when it comes to the top of the

clarifier.

Almost all the settle able materials settle down in the clarifiers and clean water are

collected to the filters.

Minimum flow velocity of 8.9 ft/hr with detention time 1.2 hrs & over flow rate 1333

gpd/sqft.

2.6.5 Filters

8 Nos. cells down flow conventional type rapid gravity filters.

Water from clarifier comes to the filter & passes through sand & gravel media.

All suspended materials & most of the bacteria are entrapped in filter media and clean

water is collected in the contact chamber for disinfections.

After disinfections collected in the clear well.

Each filter has an area of 480 sqft.

Filter media is sand monosized 0.85 -1.0 mm & 4' depth.

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The average loading 3.8gpm/sqft & back wash rate 20gpm/sqft.

Provision is kept for regular cleaning of filter media by back wash system.

Water from clear water channel of filter passes in a reverse direction from the bottom of

filter, cleaning the accumulated film of deposits.

To ensure top of the media adequately cleaned, an auxiliary fixed nozzle surface wash is

provided.

The back wash water passes to sludge tank & finally pumped out to river Halda.

2.6.6 Clear Well and High Lift Pump Station

Treated water from the filters is received in a 2.5 MG reservoir after disinfections in the

chlorine contact chamber.

Treated and disinfected water is pumped to the city by 4 Nos. pump duty and 1 no. stand-

by high lift pumps of capacity 3475 gpm and 320 KW each.

Chlorine contact time in the contact chamber is 30 minute at 20 mgd.

2.6.7 Chemical Facilities

Alum & lime are added to the water for aiding the flock formation & pH adjustment.

Provision is made to add alum to the water at the raw water venturi meter vault to aid in

the settling of suspended solids in the desilting basin during high turbidity.

Chlorine also injected to the water at rapid mixture and at contact chamber of clear well

for preventing any growth of algae & disinfections purpose.

Necessary storage, mixing & dosing of chlorine, alum and lime are done by pumps

centrally from the chemical building.

Re-circulation pumps of capacity 167 gpm re-circulate the alum solution within the alum

tank to promote the dissolution of lump alum to keep the alum solution mixed.

Hydrated lime is mixed by turbine impeller type mixture to make suspension of lime

slurry.

Alum & lime proportioning positive displacement diaphragm type pumps meter out the

correct Alum/lime dosage from the mixing tank.

The high capacity vacuum type chlorinators dose chlorine.

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2.6.8 Sludge and Backwash Facilities

Sludge that is collected at the bottom of clarifiers & desilting basins and back wash water

from filters is collected to sludge tank.

From where it is pumped out to the river Halda at a safe distance.

There are 4 pumps (with one standby) of each 2245 gpm at 13 ft and 30 hp capacities.

2.6.9 Power Supply and Generator

High lift pumps are operated at 3.3 KV.

Other pumps are operated at 0.415 KV.

Two 33 KV power supply from PDB directly from Madunaghat and Mohara Substation.

One stand-by diesel generator of 2500 KVA installed for use during any power failure.

2.6.10 Laboratory

The objective of the Mohara WTP is not only to provide water safe for human

consumption & appealing to consumers. But to bring the treated water quality within the

limits of the maximum allowable standards set by the World Health Organization

(WHO).

To this end laboratory in the plant is equipped with various sophisticated instruments for

regular testing of turbidity, pH, residual chlorine, alkalinity, hardness, TDS etc.

Depending on raw water quality the quantity of chemicals such as alum, lime and

chlorine are also determined through various tests.

Table 2.1 Daily Water Analysis of Mohara WTP

Sl. Parameter Unit

9.12.2009 10.12.2009

BWDS WHO

BWDS Raw

water

Treated

water

Raw

water

Treated

water

1 pH - 6.93~6.97 7.01~7.06 6.93~6.98 7.01-7.08 6.5-8.5 -

2 Turbidity NTU 60~100 0.8~0.98 60~100 0.8-0.99 10 5

3 T- Alkalinity mg/l 53~56 60~64 54~56 65-67 - -

4 Res. Chlorine mg/l . 0.61~0.69 - 0.59-0.68 0.2 -

5 Chloride mg/l 12~24 12~22 12~26 14~25 150-600 250

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Table 2.2 Weekly Water Analysis of Mohara WTP

Sl. Parameter Unit

9.12.2009 10.12.2009

BWDS WHO

BWDS Raw

water

Treated

water

Raw

water

Treated

water

1 T-Fe mg/l - 0.42 - 0.38 0.3-1 0.1-1

2 Mn. mg/l - 0.08 - 0.05 0.1 0.05-0.5

3 Coli. Bacteria Col/100

ml 2800 0 2250 0 0 0

4 TDS mg/l - 112 - 130 1000 1000

5 Ca Hardness mg/l - 25 - 31 - -

6 T-Hardness mg/l - 54 - 65 500 -

Table 2.3 Monthly Water Analysis of Mohara WTP

Sl. Parameter Unit

9.12.2009 10.12.2009

BWDS WHO

BWDS Raw

water

Treated

water

Raw

water

Treated

water

1 DO mg/l 7.8 7 8.2 7.8 6 -

2 BOD mg/l 1.1 1.01 2.2 0 0.2 -

3 COD mg/l 38 2 32 3 4 -

4 As mg/l - <0.004 - <0.003 0.05 0.01

5 Cd mg/l - <0.001 - 0.002 0.005 0.003

6 Cr mg/l - 0.002 - 0.003 0.05 0.05

7 Pb mg/l - 0 - 0 0.05 0.01

8 Zn mg/l - 0.12 - 0.2 5 3

9 CN mg/l - <0.02 - <0.01 0.1 0.07

10 F mg/l - 0.3 - 0.4 1 1.5

11 NH3-N (NH3) mg/l - 0.2 - 0.3 0.50 1.5

12 NO3-N (NO3) mg/l - 1.3 - 2.8 44 -

13 PO4 mg/l - 0.18 - 0.2 6 -

14 SO4 mg/l - 12 - 16 - 250

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2.6.11 Plant Monitoring Arrangement

PC monitoring system installed in the control room of main administrative building.

PC monitor LCD panel contains graphic display, plant alarm, and status indicators of

treatment plant process.

Plant intercoms paging systems for easy communication of the operation staffs within the

plant installed.

Table 2.4 Water Quality of Mohara Water Treatment Plant

No. Parameter Unit

Mohara Water Treatment Plant

Ba

ng

lad

esh

Sta

nd

ard

WH

O

Sta

nd

ard

Raw water

(Halda river)

Treated water

Min Max Min Max

1 Water temperature Degree

Centigrade 28 29 24 25 …… ……

2 Conductivity Micro

Siemens/cm …… …… 90 600 …… ……

3 pH NTU 6.4 7.2 6.9 7.4 6.5-8.5

4 Turbidity Mg/Liter 20 830 0.50 1.0 10 Max. 5 Max.

5 T-alkalinity Mg/Liter 34 70 35 70 …… ……

6 Calcium hardness Mg/Liter 22 28 24 30 …… ……

7 T hardness Mg/Liter 50 92 50 80 500 Max. 500 Max.

8 Ammonia-nitrogen Mg/Liter 0.2 0.4 0.2 0.4 0.5 Max. ……

9 Nitrate-nitrogen Mg/Liter 1.6 3.4 1.3 3.2 10 Max. 10 Max.

10 Phosphate Mg/Liter 0.30 0.61 0.18 1.2 6 Max. ……

11 Chloride Mg/Liter 4 200 4 200 600 Max. 250 Max.

12 Residual chlorine Mg/Liter …… …… 0.41 0.72 0.2 Min.

13 Sulphate Mg/Liter 13 28 156 20 400 Max. 400 Max.

14 Iron Mg/Liter 0.18 1.0 0.20 0.50 0.3-1.0 0.1-1.0

15 Manganese Mg/Liter …… …… 0.05 0.08 0.1 Max. 0.5 Max.

16 S.S. Mg/Liter 30 1000 1.0 3.0 10 Max. ……

17 TDS Mg/Liter …… …… 70 300 1000

Max. 1000 Max.

18 DO Mg/Liter 6.0 7.9 7.0 8.0 6 Min. ……

19 BOD Mg/Liter 0.9 1.2 …… 0.1 0.2 Max. ……

20 COD Mg/Liter 12 18 …… 2 4 Max. ……

21 Fecal bacteria Colonies /

100 ml 1800 2400 00 00 00 00

22 Arsenic Mg/Liter 0.001 0.004 0.001 0.004 0.05 Max. 0.01 Max.

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23 Cadmium Mg/Liter 0.001 0.003 0.003 0.005Max

.

0.005

Max.

24 Chromium Mg/Liter 0.004 0.009 0.008 0.05 Max. 0.05 Max.

25 Cupper Mg/Liter 0.4 0.7 0.06

26 Lead Mg/Liter 0.001 0.009 0.002 0.05 Max. 0.05 Max.

27 Mercury Mg/Liter 0 <0.001 <0.001 1 Max. 1 Max.

28 Zinc Mg/Liter 0.11 0.14 0.11 0.12 5.0 Max. 5.0 Max.

29 Cyanide Mg/Liter <0.02 …… <0.02 …… 0.1 Max. 0.1 Max.

30 Fluoride Mg/Liter 0.20 0.30 0.20 0.30 1.0 Max. 0.05 Max.

31 Trihelomethane Mg/Liter …… …… …… 0.037 …… 0.1 Max.

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Institute of Forestry and Environmental Sciences, University of Chittagong 15

CHAPTER THREE

KALURGHAT IRON REMOVAL PLANT (IRP) AND

BOOSTER STATION

3.1 General information

The second source of water of CWASA is extraction of ground water. There have more than 90

deep tube-wells in Chittagong city, by which CWASA extract ground water. The deep tube-wells

of Kalurghat region provide ground water with containing high concentration of Iron. Due to this

reason, CWASA treated this water before supply to the city dwellers. The production capacity of

Kalurghat Iron Removal Plant (IRP) is 64 MLD (Million Liter per Day) water. Now, water

supply from Kalurghat Iron Removal Plant (IRP) is 45 MLD. There have total 7 pumps which

are to create pressure in distribution line. For continuous electricity supply in this station, there

have a generator which able to supply 1750 KVA electricity during load-shedding.

3.2 Source and Treatment of Water in Kalurghat IRP

The source of water is ground water in Kalurghat Iron Removal Plant (IRP). Kalurghat Iron

Removal Plant (IRP) is treated water coming from 41 tube-wells. Among these tube-wells 39 is

in MOD-2 area and 2 in MOD-1 area. The main purpose of treatment of ground water in

Kalurghat IRP is removal of hardness of water. Hardness is the sum of all multivalent ions,

mainly calcium and magnesium. Water is considered to be hard if it contain 150 mg/l as calcium

carbonate (CaCO3) or more. Ground water also contains high concentration of carbon dioxide

(CO2). Lime is used to remove carbon dioxide (CO2) and hardness of water. Excess carbon

dioxide (CO2) concentration is reduced through aeration and also lowers lime requirements.

Calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2) compounds are able to

precipitate out of water. If non-carbonate hardness also needs to be removed from water, then

soda ash (Na2CO3) must be added to the water along with lime. Relevant chemical reaction is

given below:

Removal of Carbon dioxide (CO2):

CO2 + Ca (OH) 2 → CaCO3 ↓ + H2O

Lime

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Institute of Forestry and Environmental Sciences, University of Chittagong 16

Removal of Carbonate Hardness:

Ca (HCO3)2 + Ca (OH) 2 → CaCO3 ↓ + H2O

Calcium bicarbonate Calcium carbonate

Mg (HCO3)2 + Ca (OH) 2 → CaCO3↓ + MgCO3 + H2O

Magnesium bicarbonate Magnesium carbonate

MgCO3 + Ca (OH) 2 → CaCO3↓ + Mg (OH) 2↓

Magnesium hydroxide

3.3 Treatment Procedure

At first, extracted ground water comes to the aeration tower. There are two aeration towers. Then

water move to the sedimentation basin. Before coming sedimentation basin water mixes with

lime solution. There have two sedimentation basin, where calcium carbonate (CaCO3) and

magnesium hydroxide (Mg (OH) 2) compounds are precipitated. Then water is filtered by rapid

sand filter. There have 8 filters in Kalurghat IRP. The filtered water move to clear-well by

mixing with chlorine. Then from clear-well water move to distribution line by distribution pump.

The process is shown in a flow chart in below. (Figure: 3.1)

GROUND WATER FROM TUBE-WELL

AERATION TOWER

Lime Dosing

SEDIMENTATION BASIN

FILTERS

Chlorine Dosing

CLEAR WELL

DISTRIBUTION PUMP

TO MAIN TRANSMISSION LINE

Figure 3.1: A Flow Chart of Kalurghat Iron Removal Plant and Booster Station

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Institute of Forestry and Environmental Sciences, University of Chittagong 17

3.4 Quality of Water

Table 3.1: Quality of water before and after treatment in Kalurghat Iron Removal Plant

(IRP)

PH Fe

(mg/L)

T-Alkanity

(mg/L)

Cl2

(Mg/L)

T-

Hardness

(mg/L)

Residual

Cl2 (mg/L)

Before Filter 6.98 2.2 114 18

After Filter 7.11 1.4 118 18

Clear-well 7.21 0.72 128 20 80 0.58

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Institute of Forestry and Environmental Sciences, University of Chittagong 18

CHAPTER FOUR

MAINTENANCE, OPERATIONS AND DISTRIBUTION (MOD)

4.1 General information

This division of CWASA is responsible for the overall maintenance of water distribution in the

Chittagong city area. This division has two sections; these are MOD-1 and MOD-2.

4.2 Coverage area

MOD-1 operates the south-western part of Chittagong city from Dewanhat to Katgarh and

Katgarh to Salimpur. MOD-2 operates the north-eastern part of Chittagong city from Lalkhan

Bazar to Kalurghat, Kalurghat to Akbarshah including Chittagong Cantonment area.

4.3 Main activities:

The main responsibilities of MOD division are

Pipeline operation (such as pipe leakage mend, pipe set-up etc.)

Water distribution

Regular tube-well maintenance

Customer handling

Regeneration of tube-well.

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Institute of Forestry and Environmental Sciences, University of Chittagong 19

CHAPTER FIVE

DESIGN DIVISION

5.1 Activities

The main activity of Design Division of CWASA preserves documents of CWASA as built

drawing. These documents include pipeline design, distribution system map, treatment plant

design, tube-well distribution map, GIS data, MIS (Management Information System) Report

etc. MIS report is the total information of whole management of CWASA. This division also

arranges different training on their activity. The activity of design division of CWASA is given

in below chart (Figure No: 5.1)

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Institute of Forestry and Environmental Sciences, University of Chittagong 20

Design Division

Training M.I.S. (JICA) Bench Mark

(World Bank)

As Built

Drawing

G. I. S.

Non-Revenue

Water

Revenue Collection

Efficiency

Collection Period

No. of Permanent

Employee per %

Operating Ratio

Functioning Meter

of Installed Meter

Water Quality

Sample

Leakage Occurrence

Water Supply

Coverage

Average Tariff

Unit Production

Cost

Chief Revenue Officer

MOD-1

Accounts (M)

Mohara

Sales

Superintend Engineer

(MOD)

Secretariat

Computer Programmer

MOD-2

Accounts (Finance)

Construction Division-1

Sales

Construction Division-1

MOD-1

MOD-2

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Institute of Forestry and Environmental Sciences, University of Chittagong 21

CHAPTER SIX

CONCLUSION

5.1 Conclusion:

CWASA is one of the leading utility service provider government organizations in Bangladesh.

As a utility service Chittagong Water Supply and Sewerage Authority (CWASA) have great

contribution to development of Chittagong city. Despite of some sorts of limitation, they hardly

try to produce maximum quality water within their capacity to serve the citizens of Chittagong

city. I had the opportunity to work in this organization during my internship program. As a

student of Environmental Science, I have worked in engineering section of CWASA. During this

time I got an opportunity to observe the overall activities of CWASA specially treatment,

maintenance, operation, distribution and designing. As a utility service provider government

organization the overall management system of CWASA is well organized.

Page 29: An Internship Report on Chittagong WASA

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