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Treat, recycle sewage water

india Updated: Sep 02, 2009 01:19 IST
Bhavika Jain
Bhavika Jain
Hindustan Times
Brihanmumbai Municipal Corporation

Recognising that over 75 per cent of the water we use every day is for non-portable purpose, the civic body has decided to recycle the water that you waste every day.

The Brihanmumbai Municipal Corporation (BMC) will set up seven sewage treatment plants across the city over the next two years.

These plants will treat about 2,600 million litres of water daily to be used for non-portable purpose.

The BMC has written to the Centre for funding the Rs 1,400 crore project, under the Jawaharlal Nehru National Urban Renewal Mission.

With the city reeling under unprecedented water crisis this alternative source will help save up on the wastage of portable water for non-portable purpose.

While the demand for water in Mumbai is 4,200 million litres daily (MLD), the supply of 3,400 MLD from six lakes — Tansa, Modak Sagar, Vihar, Tulsi, Upper Vaitarna and Bhatsa —results in a shortfall of 800 MLD.

“The proposal was sent to the Centre three months ago under the Mumbai Sewage Disposal Project. Currently we only treat the sewage water to a certain stage before releasing it into the sea. But once the plants come up, we can treat it further so that it can be reused for non portable purpose,” said Additional Municipal Commissioner, (Projects), Anil Diggikar.

“We realised that a lot drinking water was being used for washing and cleaning purpose. With recycled water being used for non-portable purpose, a lot of drinking water will be saved,” added Diggikar.

However, the cost of establishing such a plant and the charges for processing water are expected to be high. The increased cost of water would translate into a higher bill for consumers.

“The cost per kilolitre (1,000 litres) of water could go up to Rs 50, compared with current rates on only Rs 3.5 per kilolitre,” said a civic official, requesting anonymity for lack of authorisation to speak to the media.

The proposal sent to the centre consists of plans based on three different technologies –Sequential Bio reactor, Moving Bed Bio reactor and Membrane treatment. The basis of all of these is reverse osmosis.

“Reverse osmosis is a very costly process as the membrane needs to be replaced at least twice a year. But the quality of water is so good that it can be used for drinking as well,” added the civic official.

Combined water stock in all the six lakes that supply water to the city is 8 lakh million litres, which will last for eight months.

The city needs 13 lakh million litres to suffice for the entire year.

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