The city’s water agency, Chennai Metrowater, is planning to construct an additional unit at its sewage treatment plant (STP) in Perungudi to improve the quality of treated water for industrial use, including construction. At present, the treated water’s quality is unsuitable for construction or industrial use.

A tender has been floated calling bids for the design, construction and commissioning of an STP unit with a capacity of 0.6 million litres per day (MLD) for reuse of secondary treated water for construction purposes.

Over 105 million litres of sewage from Pallavaram municipality, Alandur and other southern areas reach the treatment plant in Perungudi. Through the ‘activated sludge process,’ raw sewage is first filtered and separated from solid dirt.

The sludge left behind from the subsequent processes is used to generate biogas, which in turn generates electricity.

As of now, several million litres of treated sewage water that could be used for construction and other industrial purposes are let into Buckingham Canal and subsequently the Bay of Bengal.

Only the Tamil Nadu Road Development Corporation collects a few lorry-loads of the treated sewage to water plants on roads under its maintenance.

The proposed plant would make it possible for the treated sewage to be used directly for construction purposes. Also, the treated sewage would be of such high quality that after reverse osmosis, it could even be used for household purposes like gardening, officials said.

Metrowater has chosen to establish the additional facility at Perungudi as construction activity is concentrated around OMR and southern suburbs, officials said.

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