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Water Desalination in Gujarat

By Lalitha Vaidyanathan
AN alarming fall in the water tabic in the coastal region of Gujarat is creating problems of unprecedented magnitude for the State Government To compound matters. Increase tn the number of salt pans covering vast areas along the coast has rendered the available water brackish and saline, thereby turning the region largely un cultivable and unproductive.
Certain coastal areas In Tamil Nadu also face a similar problem. To counter this situation. a project blueprint has been prepared by an environmentalist Rear Admiral J. N. Buxl and submitted to the Gover-nment recently. Titled "Desalination of Water for Augmenting Water Resources in Saurashtra and Kutch". It Is oddly enough based on a report tilted "Nuclear-power Agro-lndustry Complex", prepared by the Bhabha Atomic Research Centre (BARC) way back in 1970.
According to the proposal, application about 50 MW of electricity in desalination in any commercial power plant, could yield one million tonnes of salt, besides 750 million litres of fresh water per day, as also enough water for irrigating 16.500 hectares of land. The minimum domestic requirement of water has been estimated to be 50 litres per individual per day.
The BARC report had similarly competed an output ratio of 19.50 per cent on its project. It pointed out that a pipeline would have to be laid between Bhimgaja-Mlthikhan lakes and the Slkka Thermal Station in the State to avoid the cost of creating fresh wa ter storage capacity for the agro-based complex.
Insofar as application of this technology is concerned, the problem does not rest on lack of know-how. In fact, there are several other, equally effective, ways of removing salt from sea water, such as are practised tn countries of the Middle East, the Carribean. Mediterranean and certain island nations as Malta. Bahrain and Japan. The question now is to Identify an appropriate cost-efficient and long-standing method that would permanently solve the water problem of coastal Gu
Desalination undertaken in India so far has been through the utilisation of a very rudimentary technology It Involves heating sea water till It evapo rates leaving behind, salt. The water- vapour 1s then cooled until it condenses into fresh water. This Is actually a distillation process and is applied by all the ships of the Indian Navy for supplies of potable water on high seas.
BARC has recently devised and Installed a multi-stage flash (MSF) unit for desalination with a capacity of producing 425 cubic metres of fresh water per day of an overall purity of 30 ppm (parts per million) of TDS (total dissolved solids), as against a permissible level as high as 1000 TDS. According to Dr M. P. S Ra man! of the Desalination DM-Mon of BARC, this unit can run on waste heat of a power plant or on a gas-based boiler or even electricity generated from a thermal plant.
Now. when a cheap Source of heat is not available, sea wa ter can be treated by means of another process called reverse osmosis. The water is forced at a high pressure through a semi-permeable membrane and in course of time. filtered.
The Central Marine and Salt Research Institute (CMSR1) at Bhavnagar. Gujarat haa developed a variety of semi-permeable membranes of cellulose acetate which can be used only for brackish water. BARC scientists have also developed polyamide membranes which were otherwise having to be Imported for desalination plants. These membrane* are undergoing pilot trials, in which they are proving 'quite effective".
Yet another destination process in use relies on solar power. Energy from the sun's rays Is collected through glass lubes and used for 'flash evaporation" of sea water.
— PH Feature.'