For those of us old enough to remember those TV commercials for Morton’s Salt showing the little girl carrying an umbrella in the rain the slogan “When It Rains It Pours”® reminds us of salt. Salt seems to be one of those things we have plenty of, but not so with water.
About 70% of the earth’s surface is water and about 96% of all of earth’s water is contained in the oceans. That means most of earth’s water is salt water. With the increasingly serious drought conditions, particularly in California, the discussion turns to where can they get more potable (drinkable) water? The word that comes up is desalinization. That is defined as removing the salt from ocean water and processing it for human consumption.
The term for the process has three accepted forms desalination, desalinization, and desalinisation according to Wikipedia. There are actually a few ways to remove minerals including salt from sea water. Quoting Wikipedia directly: “The traditional process used in these operations is vacuum distillation– essentially the boiling of water at less than atmospheric pressure and thus a much lower temperature than normal. This is because the boiling of a liquid occurs when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Thus, because of the reduced temperature, low-temperature “waste” heat from electrical power generation or industrial processes can be used. The principle competing processes use membranes to desalinate, principally applying Reverse osmosis technology. Membrane processes use semipermeable membranes and pressure to separate salts from water.Reverse Osmosis plant membrane systems typically use less energy than thermal distillation, which has led to a reduction in overall desalination costs over the past decade. Desalination remains energy intensive, however, and future costs will continue to depend on the price of both energy and desalination technology.”
According to Christopher Gasson of Global Water Intelligence around 1% of the world’s population depends on desalination for their daily need for water, but he states that by 2025 about 14% of the world’s population will be dealing with a shortage of water. It is reported by the International Desalination Association 15,988 desalination plants were operating worldwide as of June 2011 providing fresh water to 300 million people at a rate of 66.5 million cubic meters per day. That number was updated in 2013 to 78.4 million cubic meters. Ras Al Khair, Saudi Arabia is the single largest desalinization project so far producing 1,025,000 cubic meters over 2014. The country producing the highest percentage of their water using these plants is Israel which produces 40% of its water through desalinization.
In a March 30, 2015 article by Daniel Potter of KQED Science titled ” Why Isn’t Desalination the Answer to All California’s Water Problems?” Potter discusses the municipalities in California and the attempts of some of them to produce fresh water from the ocean. The city of Carlsbad, California will have the nations largest desalination plant when it is completed producing 7% of San Diego County’s water. Another plant built in the 1990s because of drought in Santa Barbara, California shut down when the rains returned, but may be reactivated soon due to the current drought conditions. It would produce 30% of the city’s water.
The military has been using desalination for many years on their ships and submarines to produce potable water for drinking, cooking and bathing while at sea.To sum it up this means that taking the salt out of sea water is a very expensive process that depends on many things. There is an old saying that necessity is the mother of invention so when the need for potable water in California or anywhere else in the world becomes extreme the need will probably out way whatever the cost may be.
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