‘Using treated wastewater is key to easing the pressure on freshwater in Chennai’

The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) currently supplies about 1,313 million litres per day (mld) of water to the city, of which around 83 mld is treated water. Shifting industries, construction activities, and large commercial establishments to treated water could significantly reduce pressure on the city’s limited freshwater sources, said Gaurav Kumar, Executive Director, CMWSSB, on Tuesday.

In a panel discussion on ‘Recycling, Recharging, Restoring The New Imperatives for Water Management’ at The Hindu Sustainability Dialogue, held in partnership with Saveetha Institute of Medical and Technical Sciences (SIMATS), Mr. Kumar said the city already had a substantial installed water treatment capacity that was not being fully utilised. Treated wastewater, which costs far less than desalinated water, was the most immediately available option to meet non-potable demand, he said.

Surface water, Mr. Kumar pointed out, depended entirely on rainfall, and while creating new reservoirs was possible, it was a long-term solution. Desalination, though important, involved high capital costs, long gestation periods, and heavy power consumption. Desalinated water costs the CMWSSB around ₹45 per kilolitre, compared with ₹4–₹5 per kilolitre for treated wastewater, he said.

Mr. Kumar said demand reduction had to precede recycling and reuse. “Even small individual actions could add up. Imagine, if randomly from tomorrow 50 lakh residents out of 90 lakh in Chennai decide to save a litre of water per day, the city will save 5 mld, enough to meet the daily needs of seven thousand families,” he said.

Speaking about the use of technology improve efficiency of water management and reduce losses, Mr. Kumar said electromagnetic bulk flow meters had been installed across water treatment plants, distribution networks, sewage pumping stations, and sewage treatment plants to monitor flow and detect leakage. In addition, internet of things-enabled ultrasonic sensors have been installed at around 300 sewage pumping stations, enabling real-time monitoring of sewage levels.

Automation of_{pumps, diesel generators, and power backup systems has reduced dependence on manual intervention, while a GIS-based mapping system is being used to coordinate with other civic agencies and prevent damage to underground pipelines during infrastructure works, Mr. Kumar explained.}

Speaking on industrial water use, he said urban water stress could only be addressed through a combination of reducing consumption and increasing reuse. Industries account for about 330 mld of Chennai’s daily water demand, and shifting them to treated wastewater could ease pressure on freshwater sources.

Beyond industrial reuse, treated wastewater can be used effectively for a range of urban purposes, said Shailesh Kumar, CEO (India Cluster), VA Tech WABAG Limited. “In my own office, for instance, we operate as a water-positive building, drawing no water from external sources — domestic needs are met through recycled water, while rainwater is recharged into the ground,” he said.

Calling for greater public awareness, better standards, and wider acceptance of reuse, Mr. Shailesh said construction was another critical area where treated wastewater should be prioritised through regulation and enforcement, particularly for roadworks and large infrastructure projects.

Vidhyalakshmi Sivakumar, professor and associate dean, Department of Civil Engineering, SIMATS, spoke on the role universities could play beyond teaching. Large campuses function as small cities, she said, consuming water, generating wastewater, and managing reuse on site.

She cited the example of an on-campus sewage treatment plant at SIMATS, designed and implemented by students and faculty, which reduced freshwater consumption by nearly 20%, offering both practical learning and a model that cities could replicate.

Rainwater conservation could not be the responsibility of government agencies alone, said Beemaraja Sakthivel, director, Stone Hands Project Consultancy. Rooftops, parks, playgrounds, and other open spaces needed to be used to store rainwater and recharge aquifers.

Chennai’s water stress, Mr. Sakthivel said, was not due to lack of rainfall but poor conservation. The city receives an average of 1,250 mm of rain annually, amounting to 50–60 thousand million cubic feet (TMC) of water, while its annual requirement is only about 12 TMC. Floods followed by droughts were the result of rainwater being drained away instead of being stored or used to recharge groundwater, he said.

Mr. Sakthivel said the spread of impermeable surfaces had reduced cities’ ability to absorb intense rainfall. With most urban areas now covered by concrete, approaches such as the Sponge City model, which focused on capturing rain where it falls through storage and recharge, were becoming increasingly necessary.

The session was moderated by K. Lakshmi, Deputy Editor, The Hindu.

Published – January 07, 2026 12:11 am IST