ABSTRACT
Desalination has progressed significantly since the simple distillation techniques first used for producing small quantities of drinking water from sea or saline ground waters. Distillation is normally now only applied to sea waters and the most successful, reliable and widely applied technique is the multi-stage flash process, particularly in the Middle East. Improved scale control and use of materials have been the major developments with this process. A new technique usingfluidised bed heat exchange may lead to cost reductions, but this will not be fully commercial for several years. Reverse osmosis and electrodialysis, both membrane techniques, are the two most commonly applied processes for the desalination of brackish waters. Of these, reverse osmosis has been the more successful and, although a relatively new process, is now considered to be technically and commercially reliable. Developments with reverse osmosis membranes have also led to a capability of desalting sea water and several small commercial plants have been installed. It is possible that the slightly more attractive economics of sea water reverse osmosis will result in a decrease in sea water distillation applications. Electrodialysis also has the capability of treating sea water but this is not yet commercial. The other techniques of freezing and ion exchange have had little commercial impact in the desalination field.
