In two years, the city capacity to treat sewage will see a marked improvement.
Chennai Metrowater has started the process of revamping its sewage treatment plants to meet the new norms of the Central Pollution Control Board on disposal of treated sewage into waterways.
The agency has 12 sewage treatment plants spread across the city and the oldest among them is a 23 mld plant constructed in 1974. Four STPs in Alandur, Nesapakkam and Kodungaiyur would be completely dismantled and replaced with new plants of higher capacity to meet the new norms, said Metrowater officials.
However, other STPs, including Koyambedu, Nesapakkam and Perungudi, would have additional units to treat sewage. Tenders would be floated later this month seeking contractors to suggest new technology to be adopted in the existing plants.
At present, the sewage is being treated using active sludge process wherein sludge is produced during treatment. The biological oxygen demand and total suspended solids levels, which determine the quality of treated sewage, is reduced 20 mg/l and 30 mg/l. These parameters have to be further reduced to 10 mg/l as per new norms to mitigate pollution in waterways.
Use of advanced technology and upgrading the capacity of STPs would improve the quality of treated sewage by 50% and ensure better quality of recycled sewage flowing into waterways, said an official. Chennai generates about 540 mld of sewage.
The water agency provides 36 mld of recycled sewage to some of the government departments and industries in north Chennai. The remaining volume is let into the nearby waterways.
Work on the ₹500 crore project funded under Atal Mission for Rejuvenation and Urban Transformation (AMRUT) would be commenced in three months. Two new STPs coming up in Tiruvottiyur and Sholinganallur would also adopt new technology.
Meanwhile, residents demand that untreated sewage let into various waterways must also be prevented. C.R.Balaji, a resident of Mandaveli, said sewage is being released into waterways from pumping stations in Greams Road and MGR Nagar apart from residential areas.
