Chennai city waterways may carry cleaner flow with revamped sewage treatment plants set to produce better quality reclaimed water

Chennai Metrowater is upgrading existing sewage treatment plants (STPs) to meet quality norms. Seven STPs across the city are being retrofitted with Moving Bed Biofilm Reactor (MBBR) tech. The project aims to produce better quality reclaimed water with BOD levels reduced to less than 10 mg/litre. A MoU with German Water Partnership will also renovate the 23-mld plant in Nesapakkam. Once completed, Metrowater's sewage treatment capacity is expected to increase to 1,082 mld.

City waterways may carry cleaner flow as Chennai Metrowater is set to complete retrofitting work in existing sewage treatment plants in a few months.

The water agency is refurbishing the existing sewage treatment plants that were added to the network during various years. Officials of the Metrowater said the treatment technology in seven sewage treatment plants across the city was being modified to suit the new quality norms. The work to upgrade the technology has been completed in the plants in Perungudi and Nesapakkam.

The oldest one with a capacity to treat 23 million litres a day of sewage was built in Nesapakkam in 1974. Spread over 45 acres, the Nesapakkam premises has four plants, including the recently commissioned 50 mld tertiary treatment plant. The plants together treat nearly 94 mld of sewage received from various zones such as Kodambakkam and Valasaravakkam.

Work in five of the seven STPs would be completed by December this year. The project in 110 mld Kodungaiyur plant and 120 mld Koyambedu STP would be finished by March next year.

Work is in progress to upgrade the facilities in Kodungaiyur and Koyambedu plants with Moving Bed Biofilm Reactor (MBBR) technology that has effective biological treatment compared to the conventional activated sludge process adopted now in the STPs. The project is nearing completion in three plants.

The MBBR technology was adopted in the existing plants as it was found to be best suited to partially dismantle and replace some units with improved technology to comply with quality standards, officials said.

The operation of the plants and quality of treated wastewater is monitored using SCADA (supervisory control and data acquisition) online system by various agencies. The project aims to produce better quality reclaimed water. The biochemical oxygen and the total suspended solids that determine the quality of treated sewage would be reduced to less than 10 mg a litre and 20 mg a litre respectively. In Nesapakkam plant, BOD level has been reduced to less than 7 mg/litre, officials said.