From frothing to fish kills, from putrid waters to scientific reports, the city has ample proof to show how its sewage is slowly choking lakes.
Despite the best efforts to rejuvenate the Uttarahalli lake, which is one in a series of lakes connected to Dorekere and Goudanakere in south Bengaluru, sewage continues to flow in. The fault, say residents, is the shoddily constructed diversion canal. Barely a couple of feet wide and with little depth, the canal — which is supposed to take sewage away from the lake — ends up dumping a significant portion into the waterbody.
“The smell is unbearable, and we have been demanding a permanent solution by diverting a majority of the sewage into sanitary drains. Chemicals have been seeping into the lake, and mosquitoes are plenty,” said Manmohan Kumar, a resident of the area.
Nearby, the rejuvenated Dorekere, which has been in the news for multiple fish kills over the past two years, sees the sewage treatment plant being rendered ineffective. Residents said much of the sewage was being let into a diversion canal untreated — and this pours into the lake during a blockage or excessive rain. Moreover, one of the trunk sanitary lines runs through the tank-bed, and residents believe these damaged and leaky pipes further contribute to sewage entering the lakes.
The city’s most recognisable lake — Ulsoor — is one such example. The 120-acre lake is fed by two inlets. An inlet close to the MEG and Centre brings in untreated sewage from Tannery Road, Fraser Town, and Pottery Town. Consequently, this is seen in the silt trap which is now filled with garbage and sewage.
These seem to be the tale of most lakes here. Bellandur and Varthur are the most stark examples, and have been effectively reduced to cesspools prone to frothing. “Until the sewage treatment plants are built, we can considerably improve Varthur lake by ensuring none of the apartments and bulk generators release sewage into drains that feed the lakes. There needs to be an effort to drive fear into those letting sewage into the lake,” said Elangovan K., a resident who has been active in bring to the fore issues around Varthur lake.
Set up decentralised STPs: Experts
Grand ambitious projects involving construction of sewage treatment plants (capable of processing millions of litres of sewage a day) may not be the answer as these projects end up being caught in land acquisition, environment problems as well as financial constraints. Moreover, most of these STPs do not receive the sewage they are designed for.
Instead, experts suggest setting up of decentralised STPs, catering only to the sewage entering to the lake. The treated sewage must also be passed through a wetland. This system has worked wonders in Jakkur lake, which can be a model for the city.
As even decentralised STPs can be expensive, the civic authority must encourage the use of CSR funds — as what is being done in Kundanahalli lake — to ensure faster construction.
On the policy front, stringent action is possible if the Karnataka Lake Conservation and Development Authority Act 2014 is strictly enforced and those found letting raw sewage into lakes are punished. Moreover, if the Karnataka Lake Conservation and Development Authority is suitably empowered and given the licence to act freely under the mandate, then we will have a singular agency for all lakes — rather than the at least six departments that are directly responsible for some aspects of lakes.
Moreover, to curtail the frothing and foaming of lakes, expert suggest a policy to regulate detergent manufacturers to make better and more eco-friendly detergents.
Though Dorekere has been rejuvenated, sewage continues flows into it. The sewage treatment plant cannot handle the amount of sewage in the inlets. We suggest that only treated water be allowed to flows into the lake, while the rest should be diverted through a main trunk channel away from the waterbody.
B.V. Mahesh Kumar, who stays near Dorekere
Doddagubbi lake (off Hennur Road) is an example of how pollution from just one industry can kill a lake. Despite complaints, chemicals from a nearby laundry unit continue to pour into the lake. Inspecting and penalising polluters can save this 120-acre lake.
Ravi Shah, resident of Doddagubbi
The process should be decentralised as much as possible to follow the topography of the city. Identify smaller treatment plants to come up close to lakes, and make large players treat and recycle their waste. The technology and know-how is available to make sure no sewage reaches the lakes.
A.N. Yellappa Reddy, environmentalist
The sewage that enters Bellandur lake mixes with fresh water and the excess water flows downstream into Varthur lake. This is highly polluted lake in the city. In spite of agitations by residents and activists, authorities have been lethargic. It is high time the government aggressively embarked on more intensive studies and application of latest technology to resolve this issue.
Syed Muneer, former Sub-Inspector, CRPF
The sewage flow into the lakes of Bengaluru makes them stink all the time
From blue to green to black, that’s how the lakes changed colour in Bengaluru
Karnataka State Pollution Control Board monitors 75 lakes for pollution
Zero lakes are graded A, B or C (water that can be consumed without conventional treatment)
25 lakes are graded D (only for fisheries purposes)
46 lakes are graded E (controlled waste disposal)
4 lakes — Kammasandra, Thigalarapalya, Gangondanahalli, Somasundrapalya — are below E grade (virtually cesspools)
Indian Institute of Science study shows 90 per cent of lakes are fed by sewage
Low pollution: 24 lakes, including Ulsoor, Agara, Hebbal, Rachenahalli, Hessaraghatta, Yelahanka, and Dorekere
Moderately polluted: 22 lakes, including Hemmigepura, Madivala, Lalbagh, Sankey, Dasarahalli, Kaikondrahalli, and Jakkur
Highly polluted: 34 lakes, including Begur, Doddanekundi, K.R. Puram, Allalasandra, Varthur, Bellandur, and Arekere
The many instances of fish kills
May 29, 2016: Overflow of storm-water drain, carrying sewage, leads to scores of fish floating dead in Hebbal lake
March 7 and May 10, 2016: Multiple instances of fish kill seen in Ulsoor lake. Inflow of sewage, lowering of dissolved oxygen in the lake and overbreeding blamed.
March 18, 2016: Fish in Devarabisanahalli lake in Belandur become the victims of increasing pollution levels
April 23, 2015: More than 10,000 fish estimated to have died because of sewage in Dorekere
April 16, 2015: More than 700 fish die in the pond at Cubbon Park after sewage and fuel from nearby vehicles flow into the lake
January 6, 2015: Hundreds of fish die in Jakkur lake
May 30, 2014: More than 20,000 fish estimated to have died after excess sewage flow into Dorekere lake