How does desalination work?


© 2010

Only a sliver of the world’s water is fresh to begin with, and after subtracting gluttons like glaciers and ice caps, all that’s left is a drop in the proverbial bucket. Since humans and a fair portion of the planet’s plant and animal population can’t subsist on saltwater, people have long looked enviously at the sea to provide the water they require, whether it’s for drinking, hygiene, agriculture or more recently, industrial purposes.

Historically, desalination was deemed too expensive to be considered a viable large-scale option; it simply required too much energy. But newer technologies, such as reverse osmosis and multistage flash distillation, have, since the 1950s, slowly started to change that opinion, especially in places where sources of freshwater are scarce, and people are plentiful. To read more about the actual processes at work, check out How Desalination Works. But for this article, let’s take a closer look at how desalination operates in the real world.

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Take Australia, for example. At the Water Services Association of Australia, employees consider their arid continent a forecast for what may be the future of water supply systems in an increasingly hot and dry world. In the midst of an extended drought, the country’s five largest cities began preparing for water shortages by building massive desalination plants for $13.2 billion [source: New York Times]. The plants certainly have their critics — citizens complaining about higher water bills, conservationists arguing against the environmental effects of the plants, and economists saying other options would have been more fiscally responsible. But according to regional water authorities, the area is now set to handle drought and water supply issues well into the future.

Israel is another instance of desalination in action. Among the many nations in the Middle East attempting to ward off water shortages, Israel is counting on desalination plants. The third of five major plants planned off the coast of Israel went into operation in January 2010, and, for now, it’s the largest reverse osmosis desalination plant on Earth. Once all the facilities are complete, they’re expected to provide about two thirds of the country’s drinking water [source: Associated Press].

Desalination techniques are also being developed on a much smaller scale. Portable desalination kits are a prime example. Researchers at MIT are working to bring desalination down to the nano level, harnessing electrostatic ion-selective membranes to avoid requirements and disadvantages often associated with the reverse osmosis method, like the need for high levels of pressure and the occurrence of inadvertent clogs and foulings. They call the process ion concentration polarization, and they envision it helping in disaster zones. The units wouldn’t produce the vast amounts of freshwater rendered by plants, but they would be self-contained, portable and powered by solar cells or batteries. Many units could be distributed during relief efforts and provide drinkable water until infrastructure functionality was reestablished [source: MIT News].

It seems the future of desalination is wide open with different research institutions continually looking for ways to make the process more efficient and more cost effective. Sooner or later, we might enjoy the occasional long, cool sip of water that, left untreated, would have been a deadly cocktail.

Lots More Information

Related HowStuffWorks Articles

  • How Water Works
  • How Salt Works
  • How Water Filters Work
  • How Reverse Osmosis Desalinators Work
  • How does reverse osmosis work?
  • Why can’t we convert salt water into drinking water?
  • How much water is there on Earth?
  • Why can’t we manufacture water?
  • Exactly what happens if we run out of water?

More Great Links

  • Intergovernmental Panel on Climate Change
  • UNESCO World Water Assessment Program
  • United Nations Development Program

  • “Desalination.” Encyclopedia Britannica.” (Sept. 20, 2010)
  • Dove, Laurie. “How Desalination Works.” June 18, 2010. (Sept. 20, 2010)
  • Chandler, David. “A system that’s worth its salt.” MIT News. March 23, 2010. (Sept. 20, 2010)
  • Frederick, Kenneth. “America’s Water Supply: Status and Prospects for the Future.” Consequences, 1, 1. Spring 1995. (Sept. 20, 2010)
  • Jehl, Douglas. “Tampa Bay Looks to the Sea to Quench Its Thirst.” New York Times. March 20, 2000. (Sept. 20, 2010)
  • Onishi, Norimitsu. “Arid Australia Sips Seawater, but at a Cost.” New York Times. July 10, 2010. (Sept. 20, 2010
  • Schulte, Bret. “A World of Thirst.” Us News and World Report. May 27, 2007. (Sept. 20, 2010)
  • Schirber, Michael. “Why Desalination Doesn’t Work (Yet).” June 25, 2007. (Sept. 20, 2010)
  • Slater, Grant. “Israel dedicates huge sea-water purification plant.” Associated Press. May 16, 2010. (Sept. 20, 2010)
  • “The World is Thirsty Because the World is Hungry.” Food and Agriculture Organization. 2009. (Sept. 20, 2010)
  • U.S. Congress, Office of Technology Assessment. “Using Desalination Technologies for Water Treatment.” U.S. Government Printing Office. March 1988 (Sept. 20, 2010)
  • Water Science and Technology Board. “Desalination: A National Perspective.” The National Academies Press. 2008. (Sept. 20, 2010)
  • “Water Supply System.” Encyclopedia Britannica. (Sept. 20, 2010)
  • “What price water transparency?” WA Today. Sept. 10, 2010. (Sept. 20, 2010)


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