CHENNAI: Untreated sewage water is being discharged into Putlur Lake in Tiruvallur district and in-turn polluting the Cooum, according to the Tamil Nadu Pollution Control Board (TNPCB). The discharge originates from a sewage treatment plant (STP) in Periyakuppam, which handles the sewage from Tiruvallur municipality areas.
In an RTI reply, TNPCB noted that during their inspection conducted between September 24 and October 15 at the STP in Periyakuppam, which is under the municipality’s control, improper sewage management and untreated sewage discharge into Putlur lake were observed.
Speaking to TNIE, a TNPCB official said, “Following the findings, we have issued strict instructions to the Tiruvallur municipality to rectify the deficiencies and to ensure that no untreated sewage is discharged into the water bodies.”
The construction of the STP had begun in 2010 under the underground sewerage scheme at Rs 54.8 crore. The plant, with a treatment capacity of 6.2 MLD, was established in 2014 without the ‘consent to operate’ from TNPCB.
An official working at the STP told TNIE that the facility currently receives an inflow of about 5.5 MLD of sewage.
“However, as the existing plant has failed and the sewage is not being treated properly. As a temporary measure, we are adding bacteria to the sewage at pumping stations before it is pumped to the plant. Extreme greenish discharge from STP was suspected to be due to excessive bacterial growth,” the official said.
When TNIE visited the STP, it observed that raw sewage water remained stagnant inside the plant premises. While the treated sewage water is colourless, discoloured water was also continuously leaking into the lake from an outlet pipeline.
D Anandhakrishnan, a resident of Manavala Nagar in Tiruvallur who applied for the RTI, said that Manavala Nagar does not have an underground drainage system. As a result, sewage from several households was already being illegally discharged into stormwater drains, which ultimately flows into the Cooum river.
Aravind Chandramohan, another resident said, the Tiruvallur stretch of Cooum river, unlike the heavily polluted Chennai, still remains clean and is used as a source of groundwater recharge. However, the illegal sewage discharge has begun to contaminate it. “During the recent rain, the sewage contamination of Cooum became evident. While floodwater flowing on one side of the river was relatively clean, an intense greenish water was flowing from the lake’s surplus on the other side into the river,” he said.
Tiruvallur municipality is now establishing another STP at a 50ft distance from the existing one at an outlay of `10.5 crore. The treated water from the plant will be discharged at the downstream of the check dam across cooum river, located near Putlur, said Tiruvallur municipality commissioner N Dhamodharan.
He said the upcoming STP, based on soil bio-technology (SBT), will function as a support system to the existing facility and is not intended to handle any additional capacity. Once it becomes operational, sewage from the pumping stations will first be treated at the existing MBBR-based STP and then routed to the new SBT plant for further treatment, ensuring that no untreated water is discharged. The new STP is expected to be commissioned in the next 15-20 days, he said.