Application Note: Desalination Of Sea Water

Desalination is the name given to processes that remove salt from water. Although 70% of the world's surface is covered with water, almost all of this water cannot be used without some removal of salt. Areas with large, growing populations and little fresh water resources are increasingly turning to desalination for their water needs. Many industrial plants and electrical utilities are located by the ocean so that they can be assured of a large, dependable, fixed-cost water supply. Sea water, however, is so corrosive that it is generally more cost effective to remove the salt than to replace piping or install pipe of more resistant materials.

In a typical desalination process, raw seawater is filtered to remove solids and then combined with acid in a treatment tank. The treated seawater is heated in an evaporator, with its resulting vapor collected and recondensed in the condenser. The condenser product is fresh water, and the salt from the seawater is removed as brine. One of the problems in this process is scale formation on the hot surfaces of the evaporation equipment. Careful pH control can minimize some of the scaling problems.