The over-exploitation of existing fresh water supplies is becoming a problem in many parts of the world. There are many causes, the principle ones being population growth, demands for higher living standards, growth of both agriculture and industry, and climate change. Water shortages are forecast to increase, especially in urban areas where the demand for water is growing. Even in the UK potential problems with shortages in the water supply are starting to appear. In many areas desalination is being considered as a possible solution to the problem. In 2010 Thames Water opened the first desalination plant in the UK for the supply of drinking water.
‘Desalination’ is the term used to describe a group of processes for reducing the salt content of brackish and sea waters to turn them into a drinkable supply. There are approximately 23,000 desalination plants in more than 150 countries treating 85,000 m3/d with over half of them located in the Middle East and the number is continuously growing; in 2013-14 about 564 new plants were contracted.
All desalination processes use chemical engineering technology in which a stream of saline water is fed to the process equipment. Energy in the form of heat, water pressure or electricity is applied and two outlet streams are produced; a stream of desalinated (fresh) water and a stream of concentrated brine which must be disposed of. This review describes, with the aid of diagrams, the most commonly used processes for desalination. It also provides an historical perspective, information on trends in the application of desalination, costs and how the salinity affects the palatability of water supplies.
June 2015 – Third Edition (first published February 2006)Copies of this report are available from the Foundation price £15.00, less 10%, for FWR members.
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