CHENNAI: After TNSE reported mass fish kill at Kovalam estuary due to pollution, a team from Tamil Nadu Pollution Control Board (TNPCB) visited the estuary on Sunday evening and collected samples for lab analysis. For the past few years, Kovalam estuary has been reporting mass fish kill before the onset of the northeast monsoon. This is believed to have caused by pollutants draining into the estuary from upstream Muttukadu backwaters.
These pollutants create a condition known as eutrophication wherein an estuary gets enriched with minerals that induce excessive growth of blue-green algae, capable of producing toxins (cyanotoxins). This toxin can affect human beings, fish, and shellfish. When the officials visited the place, there weren’t many dead fish on the banks as the high tides had taken everything in; locals, too, had cleaned the shores up to avoid stink.
A TNPCB official claimed there were no industries nearby to discharge trade effluent into the Kovalam estuary. He, however, acknowledged that the Buckingham Canal, a carrier of sewage from unsewered areas of Chennai metropolitan and suburban areas, confluence with Muttukadu backwaters and then joins the Kovalam estuary. TNPCB chairman Supriya Sahu told TNIE that necessary action would be initiated after the team submits a detailed report.
TNIE had carried articles on how the Muttukadu backwaters were becoming a safe haven for private tankers to illegally dump untreated sewage. The Southern Bench of National Green Tribunal (NGT) had taken suo motu cognizance of the issue and formed a joint committee to investigate the matter. The panel recommended a fine of `48 lakh on three panchayats – Muttukadu, Navalur, and Padur – in Chengalpattu for failing to check the pollution.
An analysis of water samples from the backwaters had revealed that the Biological Oxygen Demand (BOD) in them didn’t meet any water-quality standard set by the Central Pollution Control Board. And the presence of coliform indicated that the pollution was primarily due to discharge of untreated sewage and leachate from the municipal solid waste along the banks. A detailed report was submitted by the committee before the NGT Bench recently.