India Sci-Tech
India develops first floating desalination plant
Apr 18, 2007 - 8:28:24 PM

New Delhi, April 18 - India has developed a floating desalination plant - the first of its kind in the world - off the Chennai coastline. With a capacity of one million litres per day, it will prepare fresh water from ocean water to address the acute potable water shortage in coastal India.

The plant has been developed by the National Institute of Ocean Technology -.

'It's a first of its kind in the world. Mounted on a barge, the plant would provide much better potable water to any state along the coastline. The floating plant can serve any mainland where deep sea water is available 30 km-40 km off the shore,' said Kapil Sibal, minister for science and technology and earth sciences here Wednesday.

'The total cost of the plant was about Rs.220 million. At present it's costing us just six paise to produce one litre of water. The plant would start its regular operations in early 2008,' Sibal told reporters.

He said the water quality would be much better than what is available today. The total dissolvable solid proportion in this water is only 10 particles per million - as against a national standard of 2,000 PPM.

The plant will be demonstrated before the media Thursday.

Sibal said NIOT embarked on the venture after the encouraging results of the indigenously designed land-based plant at Kavaratti in Lakshadweep that has been generating nearly 100,000 litres of fresh water from ocean water.

The plant is mounted on a 65-metre-long by 16-metre-thick barge. The ocean's surface water is boiled inside a vacuum container.

The vapour created in the flash boil process is condensed through a refrigeration process with the help of deep-sea water collected from nearly 600 metres below the surface of the sea.

'The deep-sea water temperature is almost three times less than that of the surface water in the ocean and it helps in the cooling process of the vapour, thus preparing fresh water,' said S. Kathiroli NIOT director.

He explained that the most complex part of the process is the withdrawal of cold water from the ocean, which requires a long pipe of one metre diameter made of HDPE pipes. HDPE pipes are manufactured in lengths of 12 metres. These have to be joined together to make a 600-metre pipe weighing 100 tonnes.

'Due to the density of the saline ocean water, the pipe floats and heavy weights have to be attached at the lower end of the pipe to straighten it. The pipe was assembled at the Ennore Port and then towed to the site and connected under the barge,' said Kathiroli while speaking to IANS.

Elaborating, he said that to carry the potable water from the barge to the shore, NIOT has developed water bags of special material that can hold 200,000 litres of fresh water.

'Since fresh water is lighter than saline water, it floats and very little power is required to tow it to the shore. Small boats would be deployed to carry water from the site,' said Kathiroli.

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