A field study by researchers at the Cochin University of Science and Technology (Cusat) has revealed that the lack of industrial activity and reduced human interference during the lockdown period have not contributed to improvement of water quality on the Pathalam-Eloor stretch of the Periyar.
Data collected by the team representing the department of marine biology, microbiology and biochemistry, Cusat, showed that the water quality had deteriorated despite expectations that the sanitary standards of the Periyar would improve during the lockdown period. The study was done on April 30 and May 1.
“The dissolved oxygen (DO) level was zero at the Pathalam bund, while the biological oxygen demand (BOD) went up to 40.59 mg/litre. At FACT, the corresponding figures were 1.63 mg/litre and 20.26 mg/litre. The primary productivity in the region also collapsed. The lockdown period has not improved the water quality of the river in the downstream zone,” said Dr. S. Bijoy Nandan, professor and head of the department of marine biology, microbiology and biochemistry.
“The spike in BOD value recorded at the three stations is an indication of high organic pollution on the stretch from various sources, including sewage waste. The increase in organic load naturally reduces the DO content in the waterbody leading to fish kill and algae boom. An isotopic analysis can determine the source and age of industrial effluents already documented in the accumulated sludge,” he observed.
Suggesting an immediate intervention by the government and the State Pollution Control Board (PCB) to restore the river to its original state, Dr. Nandan called for steps to de-silt and de-sludge waste and other settled matter from the upstream and downstream regions of the Pathalam bund. Bio-remediation measures can be taken up to check fish kills and depleting levels of oxygen, he said.
A study on fish kills on the Eloor-Edayar stretch conducted by the research team in 2015 had suggested the setting up of common treatment facilities for scientific disposal of industrial effluents and sewage generated at the level of local bodies.