Restoration of Urban lakes:a case study from Bangalore
Dr Priyanka Jamwal (ATREE, Bangalore)
Prof. Laurence Carvalho (UKCEH, Edinburgh)
[email protected] @[email protected] @LacLaurence
Bangalore’s Lakes – The Challenge
Poor quality is threatening multiple
benefits derived from the city’s lakes:
o Groundwater recharge and quality of
borehole water
o Fisheries
o Irrigation water
o Green spaces for recreation
o Biodiversity refuge in city
Phenomenal Population Growth Inadequate STP capacity
The Problem
Solutions – Beacons of hope
Questions addressed in talk
1. What does monitoring data tell us about current status and future wastewater treatment needs?
2. What is the effectiveness of wastewater treatment?
3. Goals for lake restoration?
4. Recommendations
Bellandur Lake Untreated sewage
Jakkur LakeSewage plant AND wetland treatment
Untreated “Control” Site
Community Rejuvenation Site
Photograph: Aaditya Sood
Status of Jakkur & Bellandur Lakes
1. Water quality (BOD, DO, Pathogens)
2. Ecological health (Algae)
3. Methane and other greenhouse gas emissions
Jakkur vs Bellandur plots
Inflows OutflowsCW Inflows Outflows
Biological Oxygen Demand (BOD)
Jakkur Bellandur
Drinking Water Treatment & Recreational Use: BOD target ≤3 mg/l)
Dissolved Oxygen (DO) (Midday)
Fisheries Use: CPCB DO target >4 mg/l)
Jakkur DO (Sunrise)
• Oxygen declines at night below CPCB quality target
• Reduced habitat availability for fish
Pathogens – faecal coliforms
Inflows OutflowsCW Inflows Outflows
Jakkur Bellandur
Cyanobacteria in Jakkur Lake exceed WHO high risk threshold for recreational (bathing) use
Anne DobelPhytoplankton (algae)
Jakkur: Trophic status (Phytoplankton abundance)
Phosphate variation in Jakkur lake
P-threshold for ecological response (
Methane & CO2Stella White, Julia Drewer, Carole Helfter, Amy Pickard, Sumita Bhattacharyya
Bellandur Jakkur
0
2
4
6
Methane CO2 Methane CO2
Jakkur (close up)
Wastewater treatment also greatly reduces methane emissions
Questions
2. What is the effectiveness of wastewater treatment?
3. Goals for lake restoration?
• Upgradation of Lake STP- Additional technologies for removal of Nitrogen
• Addition of EM ‘Effective Microorganisms’ balls to reduce organic matter and nutrient loads
• Around 50 EM balls and 20 liters of EM Solution at the inlet and the outlet of lake
Interventions at Jakkur Lake
Jakkur Lake
Effectiveness of STP upgrade on inflow
Effectiveness of EM balls - Questionable
(mg/l)
(mg/l)
No significant improvement in lake water quality
(mg/l)
Aerators installed at HAL + Streams Inlet (BL3). Photographs taken on 04-02-2020
Intervention at Bellandur Lake – Aerators deployed at the Inlet
Aerators installed at Koramangala-Agara Inlet (BL4). Photographs taken on 04-02-2020
Intervention at Bellandur Lake – Aerators deployed at the Inlet
No significant improvement in lake water quality
Restoration Goals –Unclear
Restoration objectives as per detailed project report (DPR)- Bellandur Lake
• Improving trophic state (water quality).
• Enhancing recreational activities (e.g. swimming, boating, fishing, bird watching).
• Enhancing lake values (historic, conservation).
• Enhancing lake use (water source).
Effectiveness of the interventions
Use Details
Raw water source (untreated) (A)pH (6.5-8.5), BOD5 (≤2 mg/l), Dissolved Oxygen (DO) (≥6 mg/l)
Total coliforms (≤50 MPN/100 ml)
Recreation (organized bathing) (B)
pH (6.5-8.5), BOD5 (≤3 mg/l)
Dissolved Oxygen (DO) (≥5 mg/l)
Total coliforms ≤500 MPN/100 ml)
Drinking water source (treated) (C)pH (6-9), BOD5 (≤3 mg/l)
Dissolved Oxygen (DO) (≥ 4 mg/l)
Total coliforms (≤5000 MPN/100 ml)
Fisheries (D)pH (6.5-8.5)
Dissolved Oxygen (≥ 4 mg/l)
Free ammonia as N (≤1.2mg/l).
Irrigation (E)
pH (6.0 to 8.5)
Electrical Conductivity (≤2250 µmhos/cm)
Sodium absorption Ratio (SAR≤26)
Boron (≤2mg/l)
Designated Best Use - Water Quality Criteria
????
https://kspcb.gov.in/CPCB-Water-Quality-Index.pdf
C
Water Quality Index
https://kspcb.gov.in/CPCB-Water-Quality-Index.pdf
Indicator SDG Indicator Type Impact Impact SDG
Nutrients, Secchi, chlorophyll-a 6 Water Quality Ecosystem health 6.4
Dissolved oxygen 6 Water Quality Food: Fishery potential 2
Faecal coliforms and pathogens 6 Water Quality Public Health 3
Cyanobacteria 6 Water Quality Public Health 3
Mosquito larvae abundance 3 Public Health Public Health 3
Fish catch per unit effort (sustainable fishery) 2 Hunger Food: fishery sustainability 8
Macrophyte species and abundance 6 Ecological Health Well-being, crops, energy 3
Greenhouse gases 13 Climate Action Climate mitigation 13
Re-defining Restoration Targets
Sumita Bhattacharyya
PhD
Solving Bangalore Lakes problem
Step #1: Create
consensus
through
participatory lake
visioning
Step #2: Establish
quantitative/
economically
feasible
goals for restoration
Step #3: Build
an evidence-
base
of solutions and
foster learning
Step #4: Build
communities
towards an
integrated
“bluegreen-
grey water
infrastructureplan”
https://www.csei.org/insights
Technologies
Instream Treatment systems
Decentralised Treatment Systems
• Freshwater savings• Improved water quality
Improvement in water quality
Engagement with stakeholders and citizens Co-developing “Water solutions” workshop with stakeholders and business,
Engagement with Citizen Groups
http://blrlakesdashboard.org/atree/lakes/#/app/welcome
Citizen Dashboard
Solutions Workshop
Solutions for Bellandur & Jakkur
Bellandur Lake• STP treatment necessary to reduce organic
loading to reduce methane emissions and stop fire and foam
• Recovery a long-term process - CW and in-stream treatments will also be necessary. Aeration to speed up recovery
Jakkur Lake• P-recovery at STP
• Constructed wetland needs upgrading and maintained regularly
Nutrient reduction (especially P)• P-recovery at STP• Effective constructed wetlands for
NO3 removal
Solutions for reducing algal blooms
Other solutions• Aerate/mix water column to
favour more beneficial algae• Hydrogen peroxide treatment• Algal harvesting for biogas
generation
Organic Pollution
Nutrient Pollution
Restored Lake
General Recommendations
• On-going investment needed in both centralised and decentralised water treatment
• Water quality standards need to be comprehensive and updated to urban context of multiple use
• Monitoring needs to be outcome focused, not just episodic reporting
• Need for rapid, publicly available data to track water quality and ecological health
Acknowledgements
• Anne Dobel• Stella White• Carole Helfter• Julia Drewer• Amy Pickard• Dan Read• Iain Gunn
• Veena Srinivasan• Durba Biswas• Shashank• Sumita Bhattacharyya• Pavan Muttepawar• Chandan Gowda• Ramya• Richu• Malkan
[email protected] @[email protected] @LacLaurence
Further Information:
Dr Priyanka JamwalProf Laurence Carvalho
mailto:[email protected]:[email protected]