Mumbai’s demand is 4,250 MLD but the supply from its six water sources is only 3,400 MLD. One of the desalination plants will be for South Mumbai and the other for the suburbs and areas outside Mumbai such as Mira-Bhayander.

“Two desalination plants have been planned, one for South Mumbai which will be handled by the BMC, and the other for the suburbs, Mira-Bhayander and cities outside Mumbai, by the MMRDA,” an official said Monday after a meeting of a government-appointed steering committee comprising officials from the Urban Development Department, the MMRDA, the BMC, BARC and ONGC.

Reverse osmosis technology would be used.

“It has to be done on a BOT (build, operate and transfer) basis as it is very costly,” the official said, adding that from the experience in Chennai, it would require around Rs 600 crore, subject to fluctuations, to set up a 100 MLD plant.

The cost of desalinated water is likely to be high and plans are to supply it to commercial projects. A time-bound programme has been drawn up, with the plants planned to be commissioned by 2013 and bids for a study to be called soon.

The sites have not been finalised and the parameters used to determine these would be availability of relatively clean seawater, a clear coastline of 100 metres, as this distance is necessary between intake and outlet, and closeness to the existing water distribution network.