TNPCB Suspects Sewage Contamination After Mass Fish Death in Ennore

Sewage contamination is suspected to have triggered a recent mass fish death in Ennore, Chennai, after the Tamil Nadu Pollution Control Board recorded depleted dissolved oxygen levels in local waters.

More than two tonnes of dead fish, including prawns and catfish, were found floating in the Kosasthalaiyar river on Sunday. The incident triggered concern among local fishers, who voiced fears that chemical contamination from nearby industries might have caused the widespread mortality.

Following the incident, Tamil Nadu Pollution Control Board officials collected water samples from five locations across the area for testing. The analysis revealed that dissolved oxygen levels had dropped below 4 milligrams per litre at two of the five sampled sites.

According to authorities, untreated sewage entering Ennore Creek is a primary suspect behind the oxygen depletion. Microorganisms rapidly consume oxygen while breaking down organic matter present in untreated sewage, leading to conditions that can suffocate aquatic life.

Tamil Nadu Pollution Control Board Chairperson Anurag Mishra stated that low dissolved oxygen levels typically occur due to three main factors: sewage contamination, reduced water flow during high tides, or sudden temperature variations resulting from hot water discharge.

Mishra noted that chemical contamination and oil spills appeared unlikely based on initial assessments. Testing showed that the pH, temperature, and other water quality parameters were within optimal ranges, making sewage contamination the leading preliminary cause.

Officials noted that several similar incidents of untreated sewage intrusion into the creek have been reported in the past. However, authorities stated that the definitive cause of the mass mortality will only be established once the fisheries department completes testing on tissue samples collected from the dead fish.