The Union Ministry of Earth Sciences (MoES) is working on a pilot project to set up the country’s first offshore desalination plant, under a long- term programme to meet the growing demand for water in coastal urban areas.
Talking to The Hindu on the sidelines of the 34th meet of the Institute of Indian Geographers here on Thursday, Secretary, Earth Sciences, Shailesh Nayak said the plant of 10 million litre capacity was expected to be set up in 18 to 24 months. “We have finalised the bid for design of the offshore structure. It will be a huge plant based on a platform to which seawater is drawn from a depth of 800 metres,” he said.
Mr.Nayak said the offshore plant would be based on the indigenous technology already in use in the three desalination plants at the Minicoy, Kavarathi and Agathi islands.
The three plants, each of 100,000 litres capacity, are based on low temperature thermal desalination (LTTD) technology under which the warm surface sea water is flash evaporated at low pressure and the vapour is condensed with cold deep sea water. A barge mounted desalination plant has also been successfully demonstrated.
Mr.Nayak said the offshore plant offered a significant advantage in the quantity of water that could be produced. “The desalination technology is already proven. But constructing an offshore plant presents a design and engineering challenge. You need a platform to which the seawater has to be drawn up through a pipe from a depth of 800 m. The huge pipe has to withstand the waves. Once the water is produced, you also have to see what to do with it. You cannot throw it back into the sea.”
Mr.Nayak said the location of the offshore plant was yet to be decided. “It has to be situated at a place where the sea is at least 1200 m deep. It also has to be near to a coastal settlement so that the water can be brought back to shore for use.”
Mr.Nayak said the Ministry was working on a scheme to prepare seismic microzonation maps for 30 cities across the country, under an extended programme to determine earthquake vulnerability in urban areas and prepare mitigation plans. “Microzonation maps have already been prepared for Delhi, Bangalore, Sikkim and Guwahati under a pilot project.”