Desalination refers to any of several processes that removes the excess salt and minerals from water in order to obtain fresh water suitable for animal consumption or for irrigation, sometimes producing table salt as a byproduct.
One way to remove brine from the water is putting water under pressure and pumping ethane through it. Almost immediately crystals appear at the top made of pure water and ethane. These crystals can be melted and then the water allowed to go into a container. Because of the structure of the molecules of this substance it only picks up water and ethane, leaving the salt behind.
Desalination for brackish water is already commonplace in the U.S., where it is used to meet treaty obligations for river water entering Mexico.
Distillation of ocean water is common in the Middle East, on ships, submarines and islands. The process used in these operations is essentially the boiling of water at less than atmospheric pressure, and thus a much lower temperature than normal. Due to the reduced temperature, energy is saved, however, bacteria are not killed therefore additional water processing is necessary before the water can be used by the public.
The price of desalination is rapidly declining. A modern, large, efficient plant is within 20% of the cost of developing a new, local source of fresh water. Desalination stills now control pressure, temperature and brine concentrations to optimize the water extraction efficiency. Other methods of desalination include reverse osmosis and pressure barrier osmosis. Nuclear-powered desalination could be very economical on a large scale.
Desalination of oceanwater is common in the Middle East (because of water scarcity) and the Caribbean, and is growing fast in the USA, North Africa, Spain, Australia and China.
Desalination of brackish water is done in the United States in order to to meet treaty obligations for river water entering Mexico.
Nuclear-powereddesalination might be economical on a large scale, and there is a pilot plant in the former USSR.
Desalination plants may use seawater (directly from the ocean through offshore intakes and pipelines, or from wells located on the beach or seafloor), brackish groundwater, or reclaimed water as feedwater.
Desalinationproductwater may be used in its pure form (e.g., for make-up water in power plant boilers) or it may be mixed with less pure water and used for drinking water, irrigation, or other uses.
Desalination plants produce liquid wastes that may contain all or some of the following constituents: high salt concentrations, chemicals used during defouling of plant equipment and pretreatment, and toxic metals (which are most likely to be present if the discharge water was in contact with metallic materials used in construction of the plant facilities).
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