The BBC has a look at a new, energy efficient desalination plant in Madras - Innovative India water plant opens in Madras.
A desalination plant which begins operating in Madras on Saturday will provide some of the cheapest drinking water in India, backers say. They say that the plant will supply 1,000 litres of drinking water for just over $1 and could well be a "template" for other coastal Indian cities.
The company behind the plant says that it is the biggest in South Asia. It will provide 100 million litres of water a day to the city by filtering sea water under high pressure.
In comparison, the government-run water board supplies about 650 million litres of water to the city's seven million residents.
"We are using the advanced reverse osmosis technology. We are purifying the water by filtering it under high pressure. Unlike other desalination plants we are not boiling the water and as a result we are saving a lot of energy," Natarajan Ganesan, Joint General Manager of the Chennai Water Desalination company told the BBC.
Mr Ganesan said that because the plant used "energy recovering technology", electricity consumption was reduced - making water produced there arguably the most competitively priced in India. "It can be competitive even when compared to supplying water from natural sources like lakes. One has to spend lot of money on transport water from lakes," he said.
The plant will process 237 million litres of sea water per day. An initial treatment will remove solids present in the water, before it is passed through a membrane under high pressure.
The plant - which cost $140m - is the joint venture between an Indian company IVRCL and Befessa of Spain. It is built under the "deboot" system - design, build, own, operate and transfer.