IntroductionIntroductionSalient Features of Powai LakeSalient Features of Powai Lake

Location : Powai Lake is located about 27 Km away in the North - East of Mumbai City

Year of construction : 1891

Catchment Area : 6.61 sq. km. and Water spread when lake is full ---2.10 sq.km.

Length of Dam : 110 Mts. (stone masonry construction)

Height of Dam : Varying from 3 Mts to 6 Mts, with top of dam is 58.5Mt.THD (Town hall Datum)

Water quality : Non potable. Used for recreation, gardening, cattle washing and fishing .

The only tourist attraction in the Heart of the city of Mumbai.

Lake water got highly polluted due to untreated disposal of sewage and garbage from nearby

residential and slum colonies.

So as to save the lake it was necessary to revive and rehabilitate it urgently.

Powai Lake under National Lake Conservation Plan.Powai Lake under National Lake Conservation Plan.

In the Year 1995 under National Lake Conservation Plan of MOEF of Govt. of India, Powai Lake of MCBM was reviewed and identified as one of the Ten major lakes in the country for revival and improvements.

A high level committee was therefore formed to check the pollution levels of the lake and to take steps to create public awareness to save the lake.

Detailed Feasibility Report (DPR) prepared by consultant M/s. Wockhardt Ltd. was approved by MOEF GOI and sanctioned Rs.6.62 Crore as grant to MCBM for implementation of the scheme on priority.

Importance and Status of Powai LakeImportance and Status of Powai Lake

Powai Lake which is located in the heart of suburban of Mumbai is surrounded by NITIE , IIT, large housing complexes and unauthorized Hutment colonies.

The water of the lake is supplied to M/s L&T company and Aarey colony for non domestic uses.

During last few decades, Population surrounding the lake has increased substantially.

Heavy siltation occurred which has an estimated quantity of 4.5 lakh Cu.M. approx.

Eutrophication of lake was observed with abundance of hyacinth & floating weeds on the surface of lake.

Dissolved Oxygen level at the bottom of lake has gone low as 0.71 mg/ltr.

[Before Revival]

MAJOR CAUSES OF DETERIORATION OF LAKE

Uncontrolled development and unauthorized quarrying activities in the catchments area.

Ingress of untreated sewage from the residential areas.

Dumping of garbage and other waste materials in the lake.

Washing of clothes, vehicles, open defecation etc. On the lakeshore.

Pollution Levels of the LakePollution Levels of the Lake

A physical and analytical survey was carried out to ascertain the pollution levels and Eutrophycation condition in the lake

Water Analysis Parameter Average Values

1) pH 7.22) Total suspended solid 43.00 mg/Ltr.3) Nitrate Nitrogen 0.23 mg/Ltr.4) Total phosphorus, 0.25

mg/Ltr.5a)D.O. (Top) 4.11 mg/Ltr.5b)D.O. (Bottom) 0.71 mg/Ltr.6a)C.O.D. (Top) 42.70 mg/Ltr.6b)C.O.D. (Bottom) 119. 00 mg/Ltr.

[Before Revival]

Sludge Analysis

Parameter Average Values

1. Total Organic Matter 42.80 %

2. Organic Nitrate 2.94 gms/kg

3. Phosphorus 5.16 gms/kg

4. Ash Content 57.20 %

[Before Revival]

Chlorophyll A Contents in Lake WaterChlorophyll A Contents in Lake Water

Sr. Sampling Site Chlorophyll A (mg/ m3)

No (Average of Three Sample analyzed)

1 Boat Club 14.68 to 18.342 Powai Garden (Hill Side) 38.66 to 55.123 Near Sonar Baug Bay 86.04 to 104.444 Kol Dongri Side 44.24 to 86.445 Road Side Near Ghat 24.22 to 42.886 Near Centre of the Lake 138.48 to 166.227 In the Lake Centre 66.88 to 84.148 IIT Side (Near Temple) 28.86 to 64.66

[Before Revival]

Scientific parameters to Establish Eutrophication Condition of the Lake Water

Tropic state Phosphorus Chlorophyll A (mg/m3) Average Maximum

Oligotrophic 4 - 10 1 - 2.5 2.5 - 8.0

Mesotrophic 10 - 35 2.5 - 8.0 8.0 - 25.0

Eutrophic 35 - 100 8.0 - 25.0 28.0 - 75.0

Hypertrophic 100 25 75

Phosphorus & Chlorophyll A levels observed in the water analysis showed that the lake was under the

Hypertrophic condition.

Scientific parameters to Establish Eutrophic Condition of the Lake Water

Tropic state Phosphorus Chlorophyll A (mg/m3)

Average Maximum

Oligotrophic 4 - 10 1 - 2.5 2.5 - 8.0

Mesotrophic 10 - 35 2.5 - 8.0 8.0 - 25.0

Eutrophic 35 - 100 8.0 - 25.0 28.0 - 75.0 Hypertrophic 100 25 75 Phosphorus & Chlorophyll A levels observed in the water analysis showed

that

the lake was under the Hypertrophic condition.

EUTROPHIC FISH PONDEUTROPHIC FISH POND

Floating Scum of decaying Algae Hot surface water drives out oxygen

Blue-green Algae Bloom shuts out sunlight excretes toxins.

Fish try to catch food on its way to bottom.

Dead algae, fish, insects and food settle at bottom.

Decaying septic sludge of decomposing fish, animals, plants, fertilizer, fish food.

Septic water… no oxygen… loaded with toxic gases & solutions from decaying organic matter.

Dead water. No living fish or animal life

Thin layer of water with oxygen suitable for fish life

Lake Revival Project Implementation StrategyLake Revival Project Implementation Strategy

The work was divided in two parts.

Part I :- Pretreatment activities.

Part II :- Contract for revival using aeration and bio- remediation technique.

Contd…

Pretreatment activities consists of:-

a) Stop entries of all untreated sewage into the lake by providing treatment facility or connect it to main sewerage system.

b) Installation of penstock gates on four major nallahs along Adi Shankaracharya Marg to prevent entry of silt and sullage water into the lake.

c) Preventing the activities like open deification, throwing of garbage, washing of cars and clothes on the bank of the lake.

Contd…

Lake Revival Project Implementation StrategyLake Revival Project Implementation Strategy

Pretreatment Activities.

Contract work consists of :--a)Collection of baseline data.b)Removal of floating and unrooted weeds.c)Providing aeration system.d)Application of speciality Bio-products for biodegradation of sludge.

The project work of revival and treatment was proposed to be executed on turnkey basis. The work was awarded to M/s. Ace Housing & Construction Pvt. Ltd. in association with M/s. Clean-flow International USA at the total cost of Rs.4.69 crore (including execution, maintenance and monitoring), who claimed to have international experience in treatment and restoration of large water bodies.

Contd…

Lake Revival Project Implementation StrategyLake Revival Project Implementation Strategy

Contract for revival using aeration & bio- remediation technique.

Water Sampling PointsI)Removal of floating water hyacinth and other unrooted weed from lake water surface :

The contract period for the project was 12 months for execution and 36 months for maintenance and monitoring. The work commenced on 20-4-2002 and completed within the stipulated period of contract i.e. on 19-4-2003.

Further the maintenance period was started from 20-4-2003 and will get over on 19-4-2006.

Aeration System:- Consisting of 6 nos of air compressors (5 HP to 40 HP capacity) installed on floating jetties & on the bank of the lake & 195 Nos of Air diffusers.

The Aeration System was operated initially for a period of 18 to 20 Hours per day & further it was reduced to 8 to 12 Hours during night time.

Contd…

Lake Revival Project Implementation StrategyLake Revival Project Implementation Strategy

NATURAL INVERSION OF POND WATERNATURAL INVERSION OF POND WATER

First dose in liquid form was spread on 18th July 2002 all over the lake @ 1.5 liters / hector.( Total quantity=300 ltr.)

Second dose was spread on 12 th Feb 2003 @ 3.33 liter / hector . ( Total quantity=700 ltr.)

On 12 th April dose of Enzyme was added to activate the bio-degradation process.Quantity-2000 Ltr.

The improvement in various parameters monitored is shown in the following table.

Lake Revival Project Implementation StrategyLake Revival Project Implementation Strategy

Application of Bio-products:--

Water sampling points for monitoring qualityWater sampling points for monitoring quality

1

23

4

5

6

7

8

9

10

Values of various parameters before the start of work and Values of various parameters before the start of work and after completion of work.after completion of work.

Sr Parameter Units Value forNo Eco-balance Value (initial) Value (final)

1 D.O./ top mg/l 5 2.87 6.85

2 D.O./ bottom mg/l 2 1.30 5.45

3 C.O.D/ top mg/l 10 to 30 57.50 20.70

4 C.O.D./ bottom mg/l 10 to 30 103.90 28.90

5 Phosphate / top mg/l 0.01 to 0.035 3.971 0.0188

6 Phosphate / bottom mg/l 0.01 to 0.035 5.618 0.0178

Contd…

Sr Parameter Units Value forNo Eco-balance Value (initial) Value (final)

07 Nitrate / top mg/l < 0.1 2.063 0.727

08 Nitrate /bottom mg/l < 0.1 3.100 0.0692

09 pH / top No 7 to -8.5 7.730 7.6010 pH / bottom No 7 to -8.5 6.980 7.88

11 S. Solids / top mg/l < 10 65.00 8.3012 S. Solids / bottom mg/l < 10 131.500

8.20

13 Chlorophyll A/ top mg/cu.m. 8 tp 25 60.00 23.9013.a. Chlorophyll A/Bottom mg/cu.m. 8 tp 25 20.720 10.00

Values of various parameters before the start of work and Values of various parameters before the start of work and after completion of workafter completion of work (contd) (contd)

Dissolved Oxygen at Bottom.Dissolved Oxygen at Bottom.

1.3

0.15

1.46

6.64

5.515.52

6.696.856.85

11.26

7.33

5.45

8.58.8

6.145.975.15

7.02

5.1

6.93

5.91

6.986.95

0

2

4

6

8

10

12

MONTHS

D.O. at BOTTOM Reqd. for BOTTOM

Dissolved Oxygen at TopDissolved Oxygen at Top

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 52.87

1.18

2.82

7.95

7.2 7.5

6.457.18

7.64

11.92

7.62

6.05

8.49.2

8.04

6.836.997.32

5.56

7.43

6.48

7.51 7.5

0

2

4

6

8

10

12

MONTHS

D.O. at TOP Reqd. for TOP

Phosphates at Top and BottomPhosphates at Top and Bottom

MONTHS

PO4 at Top PO4 at Bottom Reqd. Value

Chlorophyll-A at Top & BottomChlorophyll-A at Top & BottomC

hlo

rop

hy

ll A

(m

g/L

it)

Months

Chlorophyll A of Top Chlorophyll A of Bottom Reqd. Value

FINANCIAL STATUS OF THE PROJECT

1) Total Cost of the Project :Rs.4,69,82,000.00

2) Amount Received from MOEF :Rs.4,69,82,000.00 of Govt. of India

3) Total Expenditure Incurred :Rs.4,32,00,000.00

CONCLUSIONCONCLUSION

i. Powai lake having catchment area of 6.61 Sq. Kms & lake surface area of 2.10 Sq. Kms is improved within a period of 12 months. This is the 1st successful project executed in India using “Aeration and Bio-remediation Technique”.

ii. The status of lake was transformed from Hypertrophic condition to Mesotrophic condition.

iii. Use of the aeration and bioremediation technique was effective for improving the quality of lake water to the accepted standard for water bodies being used for fishing and recreational purposes.

iv. Though the installation cost of equipment, power and monitoring the water quality is high, the cost of maintenance is relatively low.