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.
The government-run Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) will buy the purified water for the next 25 years.
"We have agreed to buy the water from them at 48.66 rupees for 1,000 litres - meaning that it costs us just over one dollar for 1,000 litres," CMWSSB Managing Director Shiv Das Meena said.
"The water is purified and demineralised. This takes away salt, lime and other particles. The purified water meets the government standards. It tastes just like ordinary water and above all it is cheap," he said.
Chennai has been suffering from a chronic water shortage for decades. Its water needs are primarily met by lakes situated around the city. But these lakes depend on the erratic north-east monsoon.
On an average year, the monsoon brings about 100cm (39in) of rainfall, but most of this arrives over a short period - resulting in a massive run-off into the sea.
Another desalination plant with similar capability is expected to be commissioned by 2012.