Sewage treatment plants (STPs), which are over four decades old, are now getting a makeover. In this lockdown period, some of the major projects taken up by the Chennai Metropolitan Water Supply and Sewerage Board are making slow progress because of reduced workforce in the city.

In an effort to improve the treatment of sewage and to adhere to the new norms of the Central Pollution Control Board, the water board has started work to revamp the existing STPs across the city. The oldest among the STPs is the 23 million litres a day (mld) capacity plant at Nesapakkam built in 1974. Moreover, new facilities are being built with a capacity to handle 350 mld of sewage at Kodungaiyur, Nesapakkam and Perungudi.

Officials of the water board said the 12 STPs now had a capacity to treat 776 mld of sewage.

“We have made progress of 8% in the work during the lockdown period with 40-50% of workers who are staying at the site. Only about 300 labourers are involved in the project now as many migrant workers have left the city. Transportation of construction material is a challenge,” said an official.

Two plants being rebuilt

The old facilities at Kodungaiyur and Koyambedu are being dismantled and replaced with new ones with higher capacity.

Besides upgrading capacity, advanced technology would be used to improve the quality of treated sewage released into the city’s waterways.

At present, the oxygen demand and total suspended solids level, which indicate the quality of recycled sewage, are reduced to 20 mg/l and 30 mg/l. Both these parameters have to be reduced to less than 10 mg/l, according to the new norms to reduce pollution in waterways. Work is on to build another 54 mld STP in Sholinganallur to cater to the areas along East Coast Road and Rajiv Gandhi Salai.

While the lockdown period and COVID-19 crisis have slowed the ₹636 crore project, the water agency plans to accelerate the work and complete it within two years to ensure better quality of recycled sewage.

Sewage generation in the city has reduced to 500 mld from the earlier 580 mld as commercial activities have decreased, the officials added.

“We have stopped executing pipeline projects. But work to construct overhead tanks and sumps for projects in added areas such as Mathur, Madipakkam, Jalladianpet and Uthandi are in progress with minimum labourers. Nearly 43% of work has been completed so far,” the official added.