DATTA MEGHE COLLEGE OF ENGINEERING AIROLI, NAVI MUMBAI – 400 708

2011 – 2012

Civil Engineering Department

A Project Visit Report on:

Bhandup Complex – Water treatment Plant

Name: _______________________________________________________

Class: ___________ Div: __________ Roll No: _______ Batch: ________

A report submitted in partial fulfillment of the requirements of

UNIVERSITY OF MUMBAI In

ENVIRONMENTAL ENGINEERING - I

GENERAL

The Municipal Corporation of Greater Mumbai was formed way back in

the year 1865 as Mumbai’s civic body. The M.C.G.M. is variably the cradle of

Local Self Government of India. It embodies the principle of democracy of

“Governance of the People, by the people, for the people”.

Through the multifarious civic and recreational services that it provides,

the M.C.G.M. has always been committed to improve the quality of life of

Mumbai. M.C.G.M. covers an area over 437.71 square Kilometers, catering to the

civic needs of over 1.25 crores Citizens. The Corporation operates an annual

tilizati outlay of more than Rs.9,000/- crores. Most of the functions carried out by

this Corporation are service oriented. The service offered includes Sanitation,

Health (Public Health Care and Secondary Health Care Services through its

Hospitals, Maternity, Child Health Care Units, Dispensaries and Field Services)

Water, Community service, Primary Education and Town Planning etc.

The Hydraulic Engineer’s Department is the one responsible for supply of

potable to the city of Mumbai.

The present water sources are –

Tulsi 18 MLD 0.5 %

Vihar 90 MLD 2.6 %

Tansa 440 MLD 13.10 %

Modak Sagar 455 MLD 13.10 %

Upper Vaitarna 635 MLD 18.85 %

Bhatsa 1830 MLD 51.82 %

TOTAL 3368 MLD 100%

DRINKING WATER STANDARDS As per BUREAU OF INDIAN STANDARDS

(BIS 10500: 1991)

Sr.

No

Substance or Characteristic Requirement

(Desirable Limit)

Permissible Limit

in the absence of

Alternate source

ESSENTIAL CHARACTERISTICS

1. Colour Hazen units, Max 5 25

2. Odour Unobjectionable Unobjectionable

3. Taste Agreeable Agreeable

4. Turbidity NTU, Max 5 10

5. pH Value 6.5 to 8.5 No Relaxation

6. Total Hardness (as CaCo3) mg/lit., Max 300 600

7. Iron (as Fe) mg/l, Max 0.3 1.0

8. Chlorides (as Cl) mg/l, Max. 250 1000

9. Residual free chlorine mg/l, Min 0.2 --

DESIRABLE CHARACTERISTICS

10. Dissolved solids mg/l, Max 500 2000

11. Calcium (as Ca) mg/l, Max 75 200

12. Copper (as Cu) mg/l, Max 0.05 1.5

13. Manganese (as Mn) mg/l, Max 0.10 0.3

14. Sulfate (as SO4) mg/l, Max 200 400

15. Nitrate (as NO3) mg/l, Max 45 100

16. Fluoride (as F) mg/l, Max 1.9 1.5

17. Phenolic Compounds (as C6H5OH) mg/l, Max 0.001 0.002

18. Mercury (as Hg) mg/l, Max 0.001 No relaxation

19. Cadmiun (as Cd) mg/l, Max 0.01 No relaxation

20. Selenium (as Se) mg/l, Max 0.01 No relaxation

21. Arsenic (as As) mg/l, Max 0.05 No relaxation

22. Cyanide (as CN) mg/l, Max 0.05 No relaxation

23. Lead (as Pb) mg/l, Max 0.05 No relaxation

24. Zinc (as Zn) mg/l, Max 5 15

Water treatment describes those processes used to make water more

acceptable for a desired end-use. These can include use as drinking water,

industrial processes, medical and many other uses. The goal of all water

treatment process is to remove existing contaminants in the water, or reduce the

concentration of such contaminants so the water becomes fit for its desired end-

use. One such use is returning water that has been used back into the natural

environment without adverse ecological impact.

The processes involved in treating water for drinking purpose may be

solids separation using physical such as settling and filtration, chemical such as

disinfection and coagulation.

Biological processes are also employed in the treatment of wastewater

and these processes may include, for example, aerated lagoons, activated sludge

or slow sand filters.

There are two major water treatment plants namely Bhandup Complex

within the Mumbai City and Pise- Panjrapur Complex about 25 kms. from the

Mumbai City Limits. The water from Tansa, Modak Sagar, Upper Vaitarna and

part of Bhatsa (Injection) is treated at Bhandup Complex having capacity of 1910

MLD.

French company Degremont Suez, which had set up the 1910 MLD water

treatment plant at Bhandup in 1981, is Asia’s largest water treatment plant. This

plant is continuously working from last 28 years. This plant controls 70 per cent

of the city’s water supply and was recently awarded the ISO 9001-2000

certification for consistent high quality water treatment. The application of new

techniques helps to reduce the wastage of water and the plant can treat the 2100

MLD water which is greater than its designed capacity.

The combination of following processes is used for municipal drinking

water treatment worldwide:

Pre-chlorination – for algae control and arresting any biological growth

Aeration – along with pre-chlorination for removal of dissolved iron and

manganese

Coagulation – for flocculation

Coagulant aids also known as polyelectrolytes – to improve coagulation

and for thicker floc formation

Sedimentation – for solids separation, that is, removal of suspended solids

trapped in the floc

Filtration – for removal of carried over floc

Disinfection – for killing bacteria

Purification of water at Bhandup Water Treatment

Plant

Supply of Raw water from through 1 km Horse shoe tunnel to the plant

Aeration

Feeding of Coagulant (PAC) and Mixing

Flocculation cum Sedimentation

Filtration (Rapid Gravity Filters)

Disinfection (Postchlorination)

Storage and Distribution from MBR

Prechlorination of Raw water from the sources

1. Prechlorination:

The addition of chlorine at the head works of a treatment plant prior to

other treatment processes. Done mainly for disinfection and control of tastes,

odours, and aquatic growths, and to aid in coagulation and settling,

The normal dosage of this treatment plant for pre chlorination of water is

3.0 mg/l. After giving dosage to the water the water is flowed to the 1 km long

horse shoe type formation tunnel in which contact of chlorine with raw water takes

place.

2. Supply of Raw Waters from Sources to the plant:

Raw water from different sources are brought to the plant in a 1 km long

Horse shoe type tunnel by means of 4 water mains. Generally raw water of

turbidities 40 – 45 NTU during normal flow and 80 NTU during the rains.

The water is treated so as to achieve turbidity less than 5 NTU.

After reaching the treatment plant the Raw water is divided into 2 types

Inlet bays one of 3 m depth and other of less than 3 m. The water is divided into

four streams/sections A, B, C & D.

3. Aeration:

Aeration is a unit process in which air and water are brought into intimate

contact. Turbulence increases the aeration of flowing streams. In industrial

processes, water flow is usually directed countercurrent to atmospheric or forced-

draft air flow. The contact time and the ratio of air to water must be sufficient for

effective removal of the unwanted gas.

Aeration as a water treatment practice is used for the following operations:

Carbon dioxide reduction.

Oxidation of iron and manganese found in many well waters (oxidation

tower).

Ammonia and hydrogen sulfide reduction (stripping).

Aeration is also an effective method of bacteria control.

Types of Aerators:

Four types of aerators are in common use:

(i) Gravity aerators

(ii) Spray aerators

(iii) Diffusers, and

(iv) Mechanical aerators

The Treatment plant in Bhandup uses Gravity aerators in which cascade

type arrangement is made for the purpose of aeration.

Spray Aerators

4. Feeding of Coagulant and Mixing:

Accepters extensive range of high performance organic and inorganic

coagulants have been developed to significantly enhance the coagulation of

suspended solids across a range of industrial applications involving process water

treatment, wastewater and effluent treatment.

At this treatment plant the alum was used as a coagulant. But due to

advantages of PAC (Poly-Aluminum Chloride) over Alum such as efficiency and

dosage required, now a days PAC is used as coagulant.

After pre chlorination and aeration, the water comes in mixing basing. In

mixing basin PAC coagulant is added and mixed in water by creating the

turbulence by freefall of water from 0.9 m height.

After this the water is pumped in to Clariflocculator.

5. Clariflocculator:

Clariflocculator unit is a combination of both flocculation and clarification

in a single tank. This unit consists of concentric circular compartments. The inner

compartment is the flocculation chamber and the outer compartment is the

clarifier. The chemically dosed water is uniformly distributed over the surface of

the flocculation compartment for effective tilization of the available volume for

flocculation. The specially designed flocculating paddles enhance flocculation of

the feed solids. As heavy particles settle to the bottom, the liquid flows radially

outward and upward and the clarified liquid is discharged over a peripheral weir

into the peripheral launder. The deposited sludge is raked to the bottom near the

central pocket from which it can be easily discharged.

At this Treatment plant the rectangular Sedimentation tank with the circular

flocculation tank in center of it and its size is 44 m length, 44m breadth, 7.5m

depth in center and 5.5m depth in corners. The Clariflocculator is of 17m diameter

and it consists of sludge removal pump and scrapers rotating on 2-3 rpm for

removal of sludge. This treatment plant has 20 Clariflocculator of this size and its

capacity of each one is 12.5 MLD water.

The water comes into the flocculation tank from mixing basin. Some

amount of raw water is aided in to flocculator for proper formation of floc. Then

water goes in clarifier (sedimentation tank) for sedimentation.

The detention period of flocculator is 15 minutes and that of clarifier is 2

hours 15 minutes. Thus the total detention time of this Clariflocculator is 2 hours

and 30 minutes.

The quantity of sludge formed in this process is around 3% of raw water.

The process of removal of sludge is done at night only.

The water is then passed to Rapid gravity filters for filtration.

Empty Full

Night View

Different Views of Clariflocculator

6. Filtration:

Filtration is the most relied water treatment process to remove particulate

material from water. Coagulation, flocculation, and settling are used to assist the

filtration process to function more effectively. The coagulation and settling

processes have become so effective that sometimes filtration may not be

necessary.

However, where filtration has been avoided, severe losses in water main

carrying capacity have occurred as the result of slime formation in the mains.

Filtration is still essential. Rapid Sand filters are used to serve the purpose of

filtration in BWTP.

Rapid sand filters use relatively coarse sand and other granular media to

remove particles and impurities that have been trapped in a floc through the use of

flocculation chemicals – typically salts of aluminum or iron. Water and flocs flows

through the filter medium under gravity or under pumped pressure and the

flocculated material are trapped in the sand matrix.

Rapid sand filters must be cleaned frequently, once in a day, by

backwashing, which involves reversing the direction of the water and adding

compressed air. During backwashing, the bed is fluidized and care must be taken

not to wash away the media.

The process, called “BACKWASHING”, involves several steps. First, the

filter is taken off line and the water is drained down to the filter bed. Then, the air

wash cycle is started which pushes air up through the filter material causing the

filter bed to appear to boil. This breaks up the compacted filter bed and forces the

accumulated particles into suspension. After the air wash cycle stops, the

backwash cycle starts with water flowing up through the filter bed. Clean water is

passed through the filter bed in order to wash the material and remove most of the

accumulated particles. This cycle continues a fixed time or until the turbidity of

backwash water is below a set value. In some cases, the additional step of

air/water wash (simultaneously) is done after air wash cycle and followed by rinse

water wash. This useless water compared to traditional step and has higher

removal efficiency which results in the cleaner filter.

This treatment plant is having 4 stakes of rapid sand filters and each stake is

consisting of 18 numbers of rapid sand filters. Thus this plant is having total 72

numbers of rapid sand filters.

The size of each filter is 15m x 11m and it filters around 300 liter water per

second. Each filter are having 8000 numbers of filtering nozzles and filter media

of 5cm thick 4mm sand and 90cm thick 0.8mm sand. The depth of this filters are

2.5m up to the top of filter media.

Rapid Gravity Filter

7. Disinfection:

Chlorination became the accepted means of disinfection, and it is the single

most important discovery in potable water treatment. Recently, however, the

concern over disinfection by-products (DBPs) produced by chlorine has given new

impetus to investigating alternative disinfectants. Disinfection of potable water is

the specialized treatment for destruction or removal of organisms capable of

causing disease; it should not be confused with sterilization, which is the

destruction or removal of all life.

Pathogens (disease producing organisms) are present in both groundwater

and surface water supplies. These organisms, under certain conditions, are capable

of surviving in water supplies for weeks at temperatures near 21° C, and for

months at colder temperatures. Destruction or removal of these organisms is

essential in providing a safe potable water supply.

Post-chlorination is done to filtered water at Bhandup water treatment plant

is done at CCT (Chlorine Contact Tank), where more chlorine is aided to the water

for disinfection purpose and to remove pathogenic bacteria from water. The

detention period of this tank is 30 minutes.

Chlorine contact chamber

8. Storage and Distribution from MBR:

The water is then pumped to the Master balancing (MBR) reservoir from

which the water is distributed under gravity type of distribution to other 26

Elevated storage reservoirs (ESR).

In distribution reservoirs again chlorination is done for disinfection purpose

in distribution system, this process is called as “Booster Chlorination”. This time

the dosage of chlorine is around 2-3 mille grams per liter.

In water treatment plant, adequacy of water treatment from health point of

view is ensured by maintaining residual chlorine of 0.2 to 0.1 mg/l at the farthest

point of distribution system.

Internal View of an MBR

TESTING OF WATER

The Water being treated is tested at various stages of treatment which was

described above. It has facilities for carrying out tests like:

1. Turbidity:

Turbidity is measured in

NTU: Nephelometric Turbidity

Units. A digital laboratory

turbidimeter was used (as shown in

figure below) which gives turbidity

directly in NTU after placing a test

tube containing water to be tested

on left side of the device.

2. Jar Test:

The jar test is a reliable method for determining the proper chemical

dosages and conditions for coagulation of water to remove color and turbidity.

This method allows adjustments in

pH, variations in coagulant or polymer

dose, alternating mixing speeds, or

testing of different coagulant or

polymer types, on a small scale in

order to predict the functioning of a

large scale treatment operation. A jar

test simulates the coagulation and

flocculation processes that encourage

the removal of suspended colloids and

organic matter which can lead to

turbidity, odor and taste problems.

The jar test procedure involves the following steps:

1. Fill the jar testing apparatus containers with sample water. One container

will be used as a control while the other 5 containers can be adjusted

depending on what conditions are being tested. For example, the pH of the

jars can be adjusted or variations of coagulant dosages can be added to

determine optimum operating conditions.

2. Add the coagulant to each container and stir at approximately 100 rpm for 1

minute. The rapid mix stage helps to disperse the coagulant throughout

each container. Coagulants are chemical additions, such as metallic salts,

which help cause smaller aggregates to form larger particles.

3. Reduce the stirring speed to 25 to 35 rpm and continue mixing for 15 to 20

minutes. This slower mixing speed helps promote floc formation by

enhancing particle collisions which lead to larger flocs. These speeds are

slow enough to prevent sheering of the floc due to turbulence caused by

stirring to fast.

4. Turn off the mixers and allow the containers to settle for 30 to 45 minutes.

Then measure the final turbidity in each container. The final turbidity can

be evaluate roughly by sight or more accurately using a nephelometer.

3. Chlorine Content:

The orthotolidine (OT) test permits the measurement of relative amounts of

total residual chlorine, free available chlorine, and combined available chlorine.

This test has some limitations. Samples containing a high proportion of

combined available chlorine may indicate more free available chlorine than is

actually present, while samples containing a low proportion of combined

available chlorine may indicate less free available chlorine than is actually present.

Precise results depend on strict adherence to the conditions of the test. The

conditions are the time intervals between the addition of reagents and the relative

concentration of free available chlorine and combined available chlorine in

the sample and the temperature of the water. The temperature of the sample

under examination should never be above 68°F (20°C). The precision of the test

increases with decreasing temperature.

EQUIPMENT: Either a disk or slide comparator may be used in

performing the orthotolidine test. A disk comparator is shown in figure. This

comparator consists of a

standard color disk and two

sample tubes. Water to be

tested is placed in both

tubes. Reagent is added to

one and the resulting color

matched with the disk. The

other tube is placed behind

the disk to eliminate any

color error that might be

caused by turbidity in the test sample. The only reagent used is a standard

orthotolidine solution.

4. MPN Test: Coliform Bacteria Test

This test is used when the water cannot be filtered due to turbidity, high

iron, large amounts of sediment, or high non-coliform bacteria count. This test

involves incubation of measured volumes of sample in liquid nutrients which

favor the growth of any coliform bacteria present. This is a statistical method of

testing based on the number of positive tubes of media after 48 hours of incubation

and 48 additional hours of confirmation. The procedure can be represented by the

following diagram.

MPN test

CONCLUSION The Site visit to Bhandup Water Treatment plant has given us an

opportunity to think in a broader aspect of Water purification and its supply. The

in depth knowledge earned by the visit will be very useful with respect to our

studies and in the near future too.

Thank you