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 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 have 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 will 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 underway 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 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 the quality of treated wastewater are monitored using the 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, the BOD level has been reduced to less than 7 mg/litre, officials said.
Citing a recent signing of a memorandum of understanding with representatives of the German Water Partnership, officials said the 23-mld plant in Nesapakkam, which has entered its 50th year, would be renovated using German technology. A study on the operation and technology and replicable models with better efficiency will be done in the first phase. The plant’s capacity may be enhanced by using reclaimed water.
Work would be taken up in three or four months with the concurrence of the Department of Economic Affairs for funding. Once the project to strengthen the sewerage treatment infrastructure is completed, Metrowater’s sewage treatment capacity is expected to increase from the present 745 mld to 1,082 mld, officials said.
