The Kanakaneri, one of the oldest waterbody in the town, is once again in the news.

Environmental activists have come out against the government's decision to establish a sewage treatment plant on Kanakaneri under the Comprehensive Sewerage Scheme.

They argue that setting up the plant will destroy the lake, which once served as the main source of irrigation for the town and its adjoining areas.

During the last several years, encroachment on the waterbody remained unchecked and desilting operations were not carried out, which led to the shrinking of Kanakaneri, president of Sembadugai Nanneeragam, Puducherry, K. Ramamoorthy told The Hindu.

“All these years we have been urging the government to strengthen the lake bunds and carry out desilting operations, but in vain. Now it wants construct a sewage treatment plant. This could completely destroy the lake,” an environmental activist said.

Though the lake had lost its storage area by several metres, it still helps re-charge groundwater, Mr. Ramamoorthy said.

However, Public Works Department officials said that the proposed plant would be established on an area of 250 m in an open space on the southern side of the bund. “There is no proposal to fill the lake for establishing the plant or to let out treated water into the water body. Setting up of the plant will help store more clean water in the lake,” a senior official in the PWD told The Hindu.

The plant will operate on Sequential Batch Reaction (SBR) method. It can reduce bacterial oxygen demand (BOD), which indicates the degree of toxic content in the treated water. If the BOD level is low, it means the toxic content is less in the treated water, he said. While the BOD level in sewage collected at the treatment plant at Karuvadikuppam and Dubrayapet was 280 million gram per litre, after treatment the BOD level would be 30 million to 40 million gram per litre.

“However, in the proposed treatment plant at Kanakaneri, the BOD level can be brought to 5 million gram per litre,” he said.

The Central Public Health and Environmental Engineering Organisation, the technical wing under the Ministry of Urban Development, has cleared the project, an official said, adding that at every stage of setting up the plant, the PWD would get the opinion of an expert team of the Indian Institute of Technology, Chennai, to ensure that all safety measures are in place.