Sludge in upstream area causing depletion of oxygen in water

Experts are debating bioremediation measures, including de-sledging the upstream areas of the Pathalam bund in the Periyar to avert fish deaths.

Mooting the idea of de-sludging the nearly 1-km upstream area, Bijoy Nandan, Associate Professor at the Cochin University of Science and Technology, said that partial bio-remediation measures could avert future fish deaths.

Sludge has settled in the upstream area leading to anaerobic conditions (depleted level of oxygen). Fish death occurs when the water with low oxygen content mixes with the water downstream following the opening of the shutters of the bund at Pathalam. De-sludging should be followed by aeration to improve the system, said Dr. Nandan, who is leading a team of researchers to suggest remedial measures for averting fish death.

Researchers from the university are collecting water samples from 16 points, both from the upstream and downstream areas of the bund, for assessing the water quality situation.

Excavators need to be deployed for removing sludge from around 500 metres of the water system. These measures together would make the water system healthy, he said.

Such measures can also win the confidence of people who are agitated over the recurring instances of fish deaths. Opening of the bunds without the introduction of such measures could again end up in mass fish kills. Bioremediation measures are followed in many parts of world for improving the health of water systems. Prevalence of anaerobic conditions in the water system can cause adverse environmental impacts, he said.

The recent fish kills had led to protests in the region with agitated environmentalists seeking action against those responsible for the incidents. They had also prevented the researchers from collecting water samples from the region.

Meanwhile, K. Sajeevan, chairman of the Kerala State Pollution Control Board, which has often been criticised for failing to check fish deaths, said that such decisions need to be taken only after detailed assessments.

Any decision to de-sludge a backwater system shall be taken only after carrying ecosystem assessments. The accumulated sludge may be washed down once the bunds are removed or opened.

The board shall come up with its stand on the issue after assessing the report prepared by the university, be said.

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