No one’s watching Chennai's sewage treatment plants

CHENNAI: The metropolis generates more than 850 million litres of sewage waste every day but only around 750 million litres are treated, which means an uncomfortable amount of untreated sewage waste is dumped into the city's water bodies on a daily basis. Also, there is no proper system in place to ensure the sewage treatment plants (STPs) are effectively treating the sewage before letting it into the city's rivers.

Of the 22 STPs in the city, maintained by Chennai Metropolitan Water Supply and Sewerage Board (Metrowater), not a single plant has an Online Continuous Effluent Monitoring System (OCEMS) to monitor the quality of the outlet water (treated water).

The sorry situation came to light after the Tamil Nadu Pollution Control Board (TNPCB) directed the water manager to ensure that instruments such as analysers and sensors are available at the STPs to measure the live status of outlet water quality parameters -- including pH, TSS (total suspended solids), BOD (biological oxygen demand), and COD (chemical oxygen demand).

"While reviewing the online connectivity of the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) STPs, it is observed that no proper connectivity of the STPs has been established with required software module and no proper data of the outlet water quality parameters of any of the STPs reach the TNPCB server," a recent communication sent by the TNPCB said.

Meanwhile, during a review meeting by the environment department in November, on the performances of OCEMS provided at the STPs, it was found that 11 of the 22 STPs are yet to establish OCEMS connectivity. Of the remaining 11 STPs, data are not available for 5 plants and data partially available but on an irregular basis. None of the STPs provides complete data.

With the capital city itself failing to effectively monitor the quality of outlet water, it is no surprise that other local bodies are following suit. Of the 68 STPs in municipal corporations, an STP in Namakkal provides real time data online. Monitoring systems in as many as 67 STPs are dysfunctional. Similarly, none of the 12 STPs in town panchayats are functional.

As per the Central Pollution Control Board (CPCB) directions issued in August 2020, all the local bodies should install OCEMS.

When contacted, a metro water official said the water manager is taking measures to provide OCEMS connectivity and release real time data as per norms.

FLOWING FOUL

-- 68 STPs in municipal corporations

-- 67 are dysfunctional

-- 1 STP in Namakkal provides real time data online

-- 12 STPs in town panchayats, all dysfunctional