Palike says no sewage entering lake, but IISc study refutes claim

Researchers from the Indian Institute of Science (IISc) collected water samples from Ulsoor lake which showed that the level of dissolved oxygen (DO) was less. The samples also show high amount of chemicals and sewage contaminants.

“Normally, the DO level should be five mg/litre or more. But at Ulsoor lake, it is 1.5- 2 mg/litre. Fish mortality highlights asphyxiation (absence of oxygen) due to enhanced biological activities. This happens when there are other organic contents in the lake because of sewage entering it,” said Prof T V Ramachandra from the Centre for Ecological Sciences, IISc.

Due to high organic input coupled with unfavourable environment (high temperature of around 34 degrees Celsius), fish kill occurs. Absence of oxygen highlights the organic load (due to untreated sewage, effluents and organic inputs with fish culture). Thus, there is a need for decentralised treatment of sewage in the City, no diversion of sewage from one region to another, enhanced aeration either through introduction of ducks or aerators/fountains, scientific management of the lake keeping in mind ecological aspects and avoiding further structural changes in lakes like creating floating restaurant.

Officials are blaming one another for the pollution in the lake and fish kill. A KSPCB official said high levels of chlorine was found in the lake (may have been put by BBMP and BWSSB to purify water).

BBMP officials maintained that no sewage was entering the lake. “Sewage has been diverted to the underground drain. Fish kill happened because of increase in temperature and drop in DO level. The algae have increased. We have no details of fish harvesting or anything as that is taken care of by the Fisheries department,” Ravindra, executive engineer of BBMP, said.

‘All agencies responsible’

BWSSB engineer-in-chief Krishnappa S said all agencies - BWSSB, KSPCB and BBMP - were at fault. While the water board should establish STPs, the KSPCB should periodically inform about the DO and other parameters. BBMP should also ensure proper waste management. There is a pipeline carrying sewage to Kommaghatta-Challaghatta valley. There is no source of water to the lake, except rain, he said. All departments and officials should be booked. Presently, there is no STP in the lake, Krishnappa added.