Report by the Kerala State Pollution Control Board regarding Periyar river pollution, 19/11/2024
Report by Kerala State Pollution Control Board (KSPCB) in Original Application No 184, 233 and 234 of 2024 (SZ) (Suo Motu Vs The Principal Secretary, Kerala & Others).
The matter related to mass fish kill in Periyar river in Kerala after suspected effluent release.
The NGT was informed that the High Court of Kerala passed an order dated June 10, 2024 directing formation of a committee. The High Court directed that the committee should file their report containing the suggestions and actions to betaken to curb the pollution in the Periyar river.
The committee filed an interim report on July 3, 2024 before the High Court of Kerala. The committee said that from the observations based on the inferences on NWMP data of the years 2022, 2023 and 2024 (January to August) fecal contamination is significant in the river. This is an indication of pollution of river from urban/domestic sources. A trend of low dissolved oxygen is seen in the river water, especially in the lower stretches during the summer months. The fish kill incident in river Periyar happened between May 20-21, 2024.
On May 20, 2024 three shutters at the Pathalam regulator-cum-bridge were opened by the Irrigation Department. It was observed that the water with high organic load and very low dissolved oxygen levels along with the settled sludge, with biological waste settled at the bottom of the bund causing anaerobic condition upstream of the bund, gushed out through the three shutters and mixed up with the saline water at the downstream side of the bund. The situation had become vulnerable because of high tide conditions on the downstream side within hours since the shutter had opened.
The reports of the Kerala State Pollution Control Board in the last few years regarding the water quality changes related to the Pathalam regulator were also examined. It has been observed that during the summer months when the bund is closed for a long time, organic wastes reach the river from several residential/commercial areas ultimately deposited at the river bed of the upstream side of the bund. Thus, the fish death was due to the sudden, continuous and strong flow of DO depleted water along with deposited sludge of high organic load that occurred when the bund was opened, which caused the drop of DO downstream of the bund.
It has been observed that the prolonged closure of the shutters in the Pathalam bund for several days results in the accumulation of organic load which subsequently causes depletion of DO levels in the upstream water of the bund. Dissolved oxygen levels at Pathalam bund downstream from April 1, 2024 to May 31, 2024 showed that the DO values at Pathalam bund upstream and downstream are very low even depleting to 'Zero level' on some days, which indicates it could be due to the discharge of untreated wastewater/sewage into the river Periyar.
It was also observed that the DO level had improved from May 23, 2024 onwards at Pathalam bund downstream - above 4 mg/L which is required for the survival of aquatic life. There are 43 effluent generating industries in Eloor Edayar industrial area. All these industries are operating with the SPCB's consent to operate. Only five industries have been permitted to discharge treated effluent with specified quality into the Periyar river. The other effluent generating industries are treating their effluent and either reusing or disposing of the treated effluent through soak pits.