CHENNAI: Construction work for expanding Metro Water board’s sewage treatment plants at Perungudi and Nesapakkam has commenced. Once these additional facilities start functioning by May 2020, quality of sewage treatment will improve to a large extent, officials said.
More capacity means a larger quantity of sewage will be treated to the desired quality before being letting out into Buckingham Canal. Also, maintenance works will be much easier. Currently, due to less installed capacity, around 20 per cent of total sewage coming to Perungudi STP is only treated partially during maintenance. Currently, Perungudi STP has a capacity to treat 136 MLD of sewage while the one at Nesapakkam can treat 117 MLD. After expansion, Perungudi STP will be able to treat an extra 60 MLD and Nesapakkam STP 50 MLD.
Last week, treated sewage coming from one of the outlet canals of Perungudi STP had a thick layer of foam on top and was letting out a foul odour too. Officials said sewage could not be treated to the desired quality due to less capacity.
“It is very difficult to clean the aeration tanks and diffusers which are central to treatment process with less capacity. But, we cannot stop incoming sewage too. After extra units are built, we will have at least 20 MLD capacity as a buffer to treat sewage when repair works are done,” said a senior Metro Water official.
Moreover, plants for tertiary treatment of sewage, based on ultrafiltration method, is also being built at Perungudi and Nesapakkam. Each will get a 10 MLD ultrafiltration plant. Such plants are to be set-up alongside 13 lakes including at Porur, Perumbakkam, and Retteri.