Each technology has advantages and disadvantages. If all things are equal with respect to supply certainty, sustainability and costs etc. seawater desalination is the correct choice as it “superdominates” (Pasacal)
Anand your topic is very interesting and useful. You may get good matter in the following :
Proceedings of conference on Desalination and the Environment sponsored by the Europian Desalination Society and centre for Research and Technology Hellas ( CERTH ) Sani Resort, Halkidiki, Grece, April 22-25, 2007.