Low cost desalination plant demo near Chennai tomorrow

New Delhi, Apr 18 (UNI) The National Institute of Ocean Technology has successfully developed and demonstrated a low cost technology for desalination of sea water that can go a long way in resolving the water problem of Chennai and other coastal areas of the country, Earth Sciences Minister Kapil Sibal announced today.

NIOT, an autonomous body under the Earth Sciences Ministry, has commissioned near Chennai (40 km offshore) an experimental floating desalination plant with a capacity of one million litres a day, Mr Sibal said at a press conference.

The institute is planning to scale up the capacity to 10 million litres a day, possibly through a joint venture with the private sector, he said.

About 25 per cent of the water requirement of Chennai could be met if the technology is adopted by the thermal plants near that city which use sea water for cooling purpose, he said.

The new low temperature technology is much better than the widely used reverse osmosis method as the purity of water is much higher, production cost is 50 per cent less, it is environmental friendly and less power-intensive.

The desalinated water produced using the technology would cost just three paise per litre on a production scale of 10 million litres a day against six paise per litre of water purified through the RO system, he said.

Similarly, only 3.5 kw/hr of power is required for producing 1,000 litres under the new technology, while 8-10 kw/hr of electricity is needed under the RO system.

The water produced under the technology is of very high purity as it contains very little total dissolved solvents (TDS) -- less than 10 part per million (ppm), against the globally accepted 500 ppm and Bureau of Indian Standards (BIS) stipulation of 2,000 ppm.

The functioning of the plant near Chennai would be demonstrated from tomorrow to various sections, including the media, Mr Sibal said.

The Chennai plant was set up after successful trials in the laboratory and an experiment on a moored barge off Tuticorin in 400 m water depth. Also, a land based plant was commissioned at Kavarati in Lakshadweep in May 2005 which is still working and so far more than five crore litres of water has been produced.

The desalinated water is brought to the mainland through water bags made of special material. Each bag can hold two lakh litres of fresh water. Since fresh water is lighter than the sea water, it floats and very little power is required to tow it to the shore. A small fishing boat can be used for the purpose.

A pipeline could be used when water is desalinated on a large scale.

Under the new technology, sea water is desalinated by flash evaporating the warm sea water (28 to 30 degree celsius on the surface) under low pressure and condensing the water vapour with the cold sea water (9 to 12 degree celsius) available at 600 metres deep.

The institute is, however, yet to develop a technology to operate such plants during the monsoon. The pipe (made up of HDPE) presently used for drawing cold water from the ocean is prone to damage at the time of storms and cyclones.

NIOT is hopeful of developing the required technology in about eight months, the Minister said.

UNI