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Process used to remove the salt from salt water or brackish water to make it drinkable or for use in irrigation.
Desalination consists of removing the salt from salt water or brackish water to make it drinkable or for use in irrigation. It is one of the ways used to combat a shortage of water by producing fresh water from seawater. However it is very costly and therefore still little used. The most commonly used techniques are reverse osmosis and distillation.
Distillation (thermal desalination) involves heating seawater until it evaporates: only the water molecules escape, leaving the salt and other substances as a deposit. The water vapour is then condensed to obtain fresh water. Reverse osmosis (membrane desalination) involves filtering seawater under pressure through a membrane that retains 90 to 99% of the salt, other substances and microorganisms. This process does however require the water to be pre-treated. The choice of technique used is made on the basis of socio-economic criteria and according to the chemical properties of the water being desalinated. The two techniques have a roughly equal share of the market and are mainly used in very rich countries such as the United Arab Emirates.