“Science and Technology” Inputs for Powai Lake Rejuvenation

1. Course Instructor: Prof. Shyam R. Asolekar
21st October, 2021
“Science and Technology” Inputs for Powai Lake
Rejuvenation
ES 645: Environmental Law & Policy
Project # 2
Umangi Mehta Roll No.: 204180002
Satyam Patel Roll No.: 203180008
Vasudev Malyan Roll No.: 19I180003

2. Introduction
• Increasing urbanisation and the ensuing imbalance between blue-green
spaces within urban ecosystems are often major elements that lead to the
degradation of surface water bodies.
• Most urban water bodies have experienced increased turbidity, algal
blooms, eutrophication, and siltation due to the discharge of untreated
sewage and partially treated industrial effluents.
• According to Asolekar (2002), untreated or poorly treated effluents
discharged into rivers and lakes, as well as run-off from urban and
agricultural regions, are the two main causes of deterioration of India's
drinking water resources.
• Lakes in India provide a variety of ecosystem services to metropolitan areas
when they are properly managed.
• Natural treatment systems (NTSs) such as constructed wetlands (CWs),
polishing ponds, and waste stabilisation ponds should be built to revitalise blue-
green spaces in urban ecosystems.
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3. Description of Powai Lake
• Powai Lake, a man-made lake in Mumbai's northern suburbs, has a water spread area
of around 2100 hectares
• It was built in 1891. It was believed to be home to 37 different fish species
• The increasing development of the surrounding areas has resulted in lake siltation,
encroachment by construction, sewage dumping, and deforestation in the area
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Location Northern suburb of Mumbai
State Maharashtra
Coordinates 19 08'N 72 54'E
Lake type Reservoir, Fresh water
Construction year 1891
Primary inflow Mithi River
Surface area 2.10 km2
Catchment area 6.61 km2
Maximum depth 12 m
Surface elevation 58.5 m
(Source: Lekshmi et al., 2021)

4. Issues of Water Quality in Powai Lake
• Powai is presently facing organic pollution threats due to the accelerated growth of
residential, commercial and industrial areas around the lake with about 22 storm water
sewer drains from nearby slums connected to Powai Lake.
• Lake encroachment is also a major concern as per Landsat MSS and Landsat 8 data
there is 26% decrease in the lake area by 2014 when compared to 1973 (Kumar & Manju,
2015; Gupta & Gupta, 2020).
• Water quality is also deteriorating over years for example: The visibility of lake has
drastic fall of about 86% from 120 cm in 1988 to 17 cm in 2017. The amount of DO had
dropped to critically low level since 1961 and the BOD levels were also found to be in
range of 27-34 mg/l which is not suitable for human consumption as per the CPCB
guidelines (Salaskar et. al., 2008 ; Usman et. al., 2018).
• As per recent reports Powai Lake has not been cleaned since 2019 and lake is over run
with hyacinth, weeds, floating garbage and plastic bottles contributing to formation of
dense layer over lake depleting oxygen and increasing eutrophication (URL 1).
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5. Objective & Criteria for Lake Rejuvenation
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The objective of a lake rejuvenation strategy is to maintain a high quality of
portable water suitable for recreation, social, industrial, agriculture as well as
domestic usage by meeting with the regulatory compliances with science and
technology inputs as shown below:
Science Technology
Aspects Of Powai
Lake Restoration
Water Quality
Improvement
Sewage And Effluent Management
Desilting & Soil Erosion
Eutrophication
Monitoring
Remote sensing
Ground Based Measurements
Other Aspects
Solid Waste Management
Urban Development
Green Buffer zone and Biodiversity
environment
Storm water and Flood Management

6. Sewage and Effluent Management
• Since the early 1970s, designed NTSs have been used into wastewater
treatment plants (WWTPs) to treat wastewater, particularly in poor Asian and
African countries.
• Small rural and semi-urban populations preferred constructed wetlands (CWs) to
treat wastewater and industrial biodegradable effluents for the elimination of
carbonaceous and nitrogenous organic contaminants.
• The treated effluents from CWs have been used to irrigate and rejuvenate lakes
in some circumstances.
• The HSSF-CWs are commonly used for the treatment and reuse of treated
wastewater, as well as the treatment of industrial effluents.
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7. Case Study: Mansagar Lake, Jaipur
• The city of Jaipur is in the state of Rajasthan and has a population of 3.1
million people.
• Lake Mansagar is a 300-acre man-made lake basin bordered by the Nahargarh
Hills, known for its outflow which supports downstream farmers.
• Lake's health has steadily declined over the last three decades, reaching
apathetic levels of degeneration due to dumping of untreated waste into the
lake year-round.
• Flagship project aimed at renewing Lake Mansagar was developed, planned,
designed, and implemented by Asolekar and co-workers under the supervision
of Prof. Soli J. Arceivala.
• The project combined environmental conservation, heritage restoration, and
commercial development.
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8. Sewage and Effluent Management
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Figure: Flow diagram of the secondary WWTP for
Lake Mansagar (Kumar et. al., 2015).
Location of WWTP HSSF-CW at
Mansagar Lake, City
of Jaipur, State of
Rajasthan, India
Capacity 7.8 MLD
% Removal of BOD5
(Average Annual
Performance)
50 – 96 %
% Removal of COD
(Average Annual
Performance)
75 – 87 %
% Removal of FC
(Average Annual
Performance)
99.99 %
Details of WWTP at Mansagar lake
(Source: Kumar and Asolekar, 2014)

9. Silting and Soil Erosion
• Silting and soil erosion are key problems with the lake. Due to siltation, encroachment,
and reclamation, the depth of Powai Lake has decreased.
• The lake has been estimated to have accumulated 3000m3 of silt.
• Desilting is the process of eliminating silt from a waterbody.
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(Source: Quadros et al., 2009)
Two methods of desilting
• Material may be pumped from
the water bed using the
Truxor's pump attachment.
• Material can be dredged from
the water bed and transferred
to its ultimate position using a
clamshell bucket attachment.
After desilting process main problem is of disposal of
silt for which
• A permeable membrane can be used to construct new
banks around the lake, by which removed silt can be
placed to create a site that can be planted to increase
both beauty and biodiversity.
• Silt may be poured into de-watering bags and allowed
to dry naturally, leaving behind a suitable planting
medium that can be utilized elsewhere on the property.

10. Eutrophication
• Eutrophication occurs as a result of this high nutrient load from sources, resulting in
unaccepted excessive plant growth, algal blooms, and fish deaths.
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Curbing the nutrient import into a lake
 In Germany, interior lakes, as well as the
North, Baltic, and Black Seas, are now
protected from nutrient pollution.
 The major method utilized to combat
eutrophication in the alpine region is a
3rd step sewage treatment plant or a
biological group treatment plant
downstream of the protected lake. These
plants receive all nutrition point sources
(Source: Klapper, 2003).
Various
technologies for
prevention and
removing of
eutrophication
Curbing the
nutrient import
into a lake
P elimination
technology
Increasing the
nutrient export
Fig: Water quality control in reservoirs by
selective off-take (Klapper, 2003)

11. Eutrophication
P elimination technology
• Phytoplankton harvesting is used in P-elimination technologies (Source: Klapper, 2003)
• Algae-rich waters are skimmed off the surface of eutrophic waterways using a special
shovel, and the algae with nutrients absorbed are mechanically redirected by filters.
Another alternative is to use P-adsorbing granules in a second filter stage
Increasing the nutrient export
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Fig: Transportable on-site
phosphorus elimination
plant PELICON
(Klapper, 2003)

12. Monitoring Technologies for Powai Lake
1. Remote Sensing Methods
• Drone surveying and Geographical
Information System (GIS) mapping
• Mod flow and Envi-Met.
• Landsat (URL 2), Google earth Pro
or Arduino based GPS system
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2. Ground Based Measurements
• As per the Guidelines of Water quality monitoring, 2017 given by MoEF & CC, all the water
bodies are required to be monitored following the Standard Methods for the Examination of
Water and Wastewater for collection of samples and analysis on site and research laboratory
by concerned department at least once in a month or but not less than 08 months in a year
(pre and post monsoon).
• The National Sanitation Foundation Water Quality Index (WQI) which is based on nine
parameters i.e., DO, faecal coliform (CFU), pH, BOD5, temperature, total phosphate, nitrate,
turbidity and sustainability can be used to classify changes in lake water quality (Uddin, 2021;
Lekshmi et al., 2021).
Figure 1.1: Development surrounding Powai lake (Source: Google earth Pro)
2000 2021

13. Other Aspects
1. Solid Waste Management :
• Robots for cleaning water surface
• Separate auto sensor Dustbins
2. Urban Development
• Repair and reconstruction of
inlets, outlets, silt traps, and lake
fence.
• Lake beatification by walking and
cycling tacks, solar lighting and
green Spaces
• Artificial ponds for religious
activities such as idol immersions.
• Decentralized water Treatment
Plants.
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Fig: Artificial Pond By
BMC (Source:
https://enewsinsight.com)
Fig: Solar powered surface
water cleaner (Source:
https://indianexpress.com)
Fig: Decentralized Water treatment system (settlement
tank or septic tank; Secondary anaerobic treatment in
baffled reactors; reed bed system (Source:
https://www.cseindia.org/decentralised-wastewater-treatment-
dwwt—1714)

14. Other Aspects
3. Storm water and Flood management
• Ballasted sand flocculation
technology to improve the settling
properties of suspended solids
through improved floc bridging (EPA,
2003; Kumar et al., 2019).
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4. Green Buffer zone and Biodiversity environment
• At least 50-100m periphery around the lake should be maintained as green belt
zone with deeply rooted plant, trees and Shrubs.
• The safe environment with adequate shelter as well as suitable environment for
rich assortment of flora and fauna including 50 species of birds and other aquatic
species (Bhagat, 2011; Lekshmi et al., 2021).
Fig: BSF technology
(Source: https://www.flickr.com/photos/)

15. Conclusion
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• Powai lake is endangered due to disposal of untreated sewage form nearby settlements,
Storm water, eutrophication and Silting of the lake. So, it is important to rejuvenate the
lake to avoid any further depreciation in quality of lake.
• The rejuvenation of Powai Lake is an integrated approach to employ science and
technology with the appropriate governance and development of business model to
enhance the sustainability of the lake.
• The science and technology inputs should be applied for restoration of overall water
quality, Monitoring and Other aspects like urban development, storm water management,
Solid waste management, lake beatification, conservation of ecology and biodiversity.
• Thus, Powai Lake rejuvenation is an Holistic approach for restoring the ecosystem using
science and technology inputs in most feasible and environmentally sustainable way.

16. References
• American Public Health Association. Standard Methods for the Examination of Water and Wastewater, 23th
ed.; Rice, E.W., Baird, R.B., Eaton, A.D., Eds.; American Water Works Association: Washington, DC, USA,
2017.
• B., Lekshmi & Saha, Dipanjan & Sutar, Rahul & Singh, Richa & Prabhu, Shardul & Kamat, Arundhati & Sharma,
Shruti & Saxena, Raghuvansh & Loiselle, Steven & Asolekar, Shyam. (2021). Science & Technology Agenda for
Blue-Green Spaces Inspired by Citizen Science: Case for Rejuvenation of Powai Lake. Sustainability. 13. 10061.
10.3390/su131810061.
• Bhagat, S. City’s Flora & Fauna Live on in Little Isles. The Times of India. 1 June 2011. Available online:
https://timesofindia. indiatimes.com/city/mumbai/citys-flora-fauna-live-on-in-little-isles/articleshow/8673663.cms
(accessed on 16 October, 2021).
• EPA, 2003 Wastewater Technology Fact Sheet: Ballasted Flocculation. EPA 832-F-03-010 Office of Waste
Management. Municipal Technology Branch, US Environmental Protection Agency, USA.
• Gupta, Parikshit, And Rishi Gupta. “Past, Present and Future of Powai Lake, [Mumbai] And Revival Through -
Holistic Analysis.” Journal of Emerging Technologies and Innovative Research, 2020.
• Kumar D. and Asolekar S. R. (2014b). Pilot-scale horizontal sub-surface flow constructed wetland to treat sewage.
• Kumar, D., & Asolekar, S. R. (2014). Significance of engineered natural treatment systems for treating sewages:
India Case Study. Manuscript in Preparation.
• Klapper, H. (2003). Technologies for lake restoration. Journal of Limnology, 62(SUPPL), 73–90.
• Kumar, Sumant & Kazmi, Absar & Ghosh, Narayan & Kumar, Vinod & Rajpal, Ankur. (2018). Urban stormwater
runoff treatment of Nainital Lake’s catchment: An application of ballasted sand flocculation technology. Water
Science and Technology: Water Supply. 19. 10.2166/ws.2018.148.
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17. References
• Kumar, R. & N, Manju. (2015). State of Water Quality of Two Tropical Urban Lakes Located at Mumbai Megacity.
International Journal of Science and Research (IJSR). 438. 1991-1998.
• Quadros, G., Gurav, G., Rasal, V., Shenal, D., & Bhagat, K. (2009). Draft report on the Study of Lakes on Mumbai .
204 National Insurance Building ,. World Wide Fund for Nature.
• Salaskar P B, Yeragi S G, Gordon Rodricks [2008]: Environmental status of Powai Lake, Mumbai [India]
Proceedings of Taal 2007, 12th World Lake conference [ed. Sengupta M & Dalwani R], 1650-1655
• Uddin Md, G.; Nash, S.; Olbert, A.I. A Review of Water Quality Index Models and Their Use for
Assessing Surface Water Quality. Ecol. Indic. 2021, 122, 107218.
• Usman, A., K. Dube, S.P. Shukla, P. Salaskar, C. Prakash, P.B. Sawant and Singh, R. 2018. Water Quality Index
as a Tool for Assessment of Status of an Urban Lake of Mumbai.Int.J.Curr.Microbiol.App.Sci. 7(4): 520-533. doi:
https://doi.org/10.20546/ijcmas.2018.704.061
URL 1: https://www.dnaindia.com/mumbai/report-analysis-finds-powai-lake-s-northern-part-most-polluted-2604215
URL 2: https://www.usgs.gov/core-science-systems/nli/landsat
.
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18. THANK YOU!
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