When the monsoon played truant in 1992, officials of the Mumbai-based Rashtriya Chemicals and Fertilizers Limited (rcf) realised that the water-dependant company had to find alternatives to municipal water supply. They proposed rcf recycle sewage to run its plants.

"The cooling towers of our plants require round-the-clock water supply. Any shortfall trips the unit; some plants take more than 2 days to recover. In 1992, our plants consumed about 28 million litres of water a day. 20 of them had to be closed down for 15 days in 1992 due to water shortages that ensued after monsoons got delayed, that year; we lost more than Rs 50 crore. It was then that we decided to think of alternatives to municipal water supply,' recalls P T Desai, deputy general manager, corporate communications, rcf .

rcf had two options: a plant to desalinate seawater, or a sewage treatment plant (stp). "Our plants require water with low levels of total dissolved solids (tds). So seawater, which has a very high tds content, was ruled out. Treating this water would have required high-energy inputs. So, we proposed an stp, ' says Desai, who was in charge of the project. "The rcf management cleared the project. But they wanted to make sure that the quality of the treated water would in no way be inferior to the water supplied by Mumbai's municipality, Brihanmumbai Municipal Corporation (bmc, now called Municipal Corporation of Greater Mumbai). So, they also asked for a reverse osmosis (ro) unit,' he adds. Armed with his superior's sanction, Desai approached bmc , which to his surprise, decided to act difficult.

But why? Mumbai's municipal corporation feared a loss in revenue. In the early 1990s, the corporation sold water to industries at Rs 22 per cubic metre (cum). The income was used to cross-subsidise domestic water supply: these consumers had to pay 60 paisa per cum. The municipality feared rcf's plans could upset this arrangement; other industries would follow its example and reduce their freshwater consumption.

The reluctant municipality finally gave rcf the green signal in 1995, but with certain conditions. " rcf had to pay the municipal corporation 60 paisa for every litre of sewage recycled. We had to sign a ten-year contract with the bmc,' says Desai.

"We agreed. N ow, the challenge was to get the sewage required by the stp: about 20 million litres, everyday,' he says. Chembur's sewage was the best option because the stp was located in this suburb of the metropolis. But things were not easy. "Our cooling plants required a constant water supply. So, the stp had to be on the job throughout the day. It, therefore, required a steady sewage supply, which the Chembur zone could not provide. Here, heavy sewage was generated only in the mornings and in the evenings,' points out Desai.

rcf then decided to tap an open nullah that carried 100 million litres of sewage, every day, from three suburbs in Mumbai