‘STPs not an ideal solution for organic pollution in city lakes’

Construction of sewage treatment plants may not be a solution for organic pollution that is plaguing the urban lakes, especially when it comes to the smaller ones with lower holding capacity.

Scientists from the Telangana Pollution Control Board (TGPCB) have drawn attention to this fact at a meeting convened by the Commissioner of the Hyderabad Disaster Response and Asset Protection Agency (HYDRAA) A.V. Ranganath on Friday, which had attendance from experts in the Irrigation and Revenue departments, and environmentalists.

The limit for Biochemical Oxygen Demand (BOD) for treated water released from STP is 10 mg per litre even by the most modern technology, but the maximum BOD required for a lake’s survival is 3 mg/l. BOD is an important parameter to determine the level of organic pollution in a water body.

“If we continuously let the treated water in, the rising nutrient levels might kill the lake if its holding capacity is lower,” said D. Prasad, senior environmental scientist from TSPCB who attended the meeting.

Speaking on the side lines of the meeting, Mr. Prasad elaborated on this, saying that water with a 3 mg/l BOD is still impure for drinking, but may be used for bathing.

“But if not diluted enough, the treated water with a BOD of 10 mg/l may increase the nutrient levels in the lake. Together with the organic matter from the dying plants in the lake, the nutrients will further rise, resulting in eutrophication and death of the lake,” he explained.

STPs, however, are the only effective solution for the rejuvenation of Musi river which does not have perennial flows from upstream.

“The river cleans itself through natural aeration process downstream. The outflows from the STPs may be channelised parallelly along the river for the aeration process to take place, and may be connected with the river where the water gets relatively better,” Dr. Prasad said, when asked about the efficacy of STPs for Musi cleaning.

The meeting dwelt majorly on the fixing of the full tank levels, which has recently been disputed in case of the Ameenpur lake.

Irrigation experts who attended the meeting, said the memoirs of the Ameenpur lake mistakenly mentioned the FTL as 93 acres, which matched with the government land inside the lake. Height of the surplus weir is the only criterion for determining the FTL, hence a probe may be conducted to know if the same is tampered with.

Published - November 23, 2024 12:59 am IST