Farmers have raised concerns over the alleged discharge of untreated sewage from the existing Sewage Treatment Plant (STP) at Panjapur into Koraiyar River, which joins the Cauvery, and have sought measures to prevent contamination of water sources downstream.

They alleged that sewage had overflowed from the treatment facility and accumulated in low-lying areas near the plant before entering the Koraiyar through a pipeline. The stagnant sewage was also causing foul odour and inconvenience to residents and passengers travelling to and from the Panjapur bus stand, they said.

Tiruchi Corporation, however, said the overflow was caused by a temporary blockage in the conduit connecting the primary treatment plant with Anaerobic Pond-2 at the existing STP. The conduit opening had become clogged with sludge and silt, restricting sewage flow into the anaerobic pond and causing backflow into the primary treatment plant, an official said.

The blockage is being cleared through desilting works and the flow into the anaerobic pond has been restored, following which the overflow from the primary treatment plant stopped, the official added.

The existing STP has a treatment capacity of 58 million litres a day (MLD) and is operating at full capacity following the expansion of the underground drainage network under the AMRUT scheme. A new 100 MLD STP is under construction at Panjapur and is expected to be commissioned within three months.

“Continuous monitoring and preventive maintenance are being undertaken to ensure uninterrupted functioning of the treatment plant. Periodical removal of sludge will also be carried out until the new STP is commissioned,” the official said.

Farmers, however, alleged that sewage from residential areas, industries and hospitals connected to the underground drainage system was overflowing from the treatment tanks. They also expressed concern over the possible contamination of groundwater sources used for drinking water supply in downstream areas.

The authorities should undertake periodic maintenance to prevent sewage from being discharged into the Cauvery and ensure that the treatment facility functions properly, said Ayilai Sivasuriyan, Tiruchi district secretary, Tamil Nadu Vivasayigal Sangam.