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As many regions experience increasing water scarcity and degradation, desalination, the method of removing salts and other impurities from seawater and brackish water, has become a significant freshwater source. Today, nearly 8.8 bil- lion gallons of seawater are desalinated every day in over 120 countries. The pros for desalination are obvious: Where there is no clean or fresh water and a dire need, technology has cre- ated some. To global water crisis newbies, desalination might appear a miracle cure-"yes, that's the ticket! We can purify saltwater-there's plenty of it!" But the realities are a little more complex. The downsides for desalination are that it's expensive, energy·intensive and it pollutes. Most developing nations can't afford the infrastructure and only countries with large oil reserves can produce energy cheaply enough to make a desalination plant cost-effective; but burning fossil fuels contributes to global warming. For every gallon of freshwater that is desalted another supersalinated gallon is returned to the sea and this can have a varying effect on the local marine life. However, if capital costs decrease and other energy sources, such as wind and solar power are considered, could desali· nation lessen the impact of the crisis? At present 10 countries account for 75 percent of the desalination worldwide, but as higher performance materials become available at lower costs-and as traditional sources run dry-countries are increasingly turning toward desalination. Israel has five new plants in development, while Cyprus is looking to implement two new plants by 2005 and the market is project- ed to grow by $10 billion over the next five years and $70 billion over the next 20. More efficient technology at lower costs as well as better planning are all contributing factors in the growth of the industry. But most experts agree that the big savings, both financially and ecologically, will come when desal plants are run on renewable energies like wind and solar. Most desalination plants still depend on energy generated by fos- sil fuels. Soteris Kalogirou, a Greek desalination scientist, has estimated that present-day distillation plants can desalinate about 90 gallons of seawater from the energy of one gallon of fuel, whereas 10 years ago that figure was 36 to 1. In 1990 it was estimated that 130 million tons of oil per year were being used to desalinate water worldwide. Since then the amount of water that is desalinated has doubled. Because of this, some critics are question· ing whether the technology will actually help us or hinder us in the long run . Canadian authors and activists, Maude Barlow and Tony Clarke write in their book, Blue Gold, "using more fossil fuels to produce fresh water out of salt water, when global warming is part of the problem of the freshwater crisis, is its own form of insanity." But in California, which has some of the most energy·intensive water in the country-much of Southern California's water has to be pumped hundreds of mile over the Tehachapi Mountains-there is already talk of using solar power to desalinate seawater. According to Andrew Shea, vice president at Poseidon Resources, a company that is developing desalination plants in Tampa Bay, Florida and Huntington Beach, California, the energy 62 required to desalinate water in California versus the amount of energy already being used to transport reservoir water isn't that great. "It's not like you're jumping into a radical new category. People always perceive that RO [desalination] is vastly more energy intensive. Our response is it used to be." Although the greatest environmental impact from desalination is through the use of fossil fuels, all desalination plants discharge a briny efflu- ent that is twice as salty as seawater, which is about 3.5 percent salt. Environmental problems can also arise through additional alkaline and chemical discharges. Environmental groups such as Defenders of Wildlife worry that if the American desalination plant in Yuma is reactivated the amount of water flowing into the Cienega de Santa Clara wetlands of Mexico could be cut by as much as 75 percent. This, combined with a significant increase in the salinity of the water flowing into the biosphere could have a drastic effect on the local marine life and the migratory birds that stop there every year. It is location and planning that often play the key role; if there isn't sufficient flow near a plant's discharge area there is often an increase in the turbidity of the water which hinders the development of algae and plankton. Further difficulties can arise if the plant is being used to desalt brackish or salty water inland. And the concentrate is not disposed of prop· erly (in most cases this means being pumped or trucked to the sea) it can contaminate ground water. Although desalination facilities in the US are usu· ally regulated at the state level, many other countries may not be covered by such strict rules. But sometimes one has to choose the lesser of two evils: in Florida overextraction of aquifer water since the 70S has resulted in the decrease of spring flows causing wetlands cypress trees to fall over dead for lack of water. In such cases, desalination could actually be an environ- mental positive. ) Aaron Clark HOW IT'S DONE? MSF Multi-Stage Flash (MSF) distillation uses heat to convert seawater into water vapor that is in tum condensed to form fresh- water. About half the world·s freshwater is produced through MSF. RO Reverse Osmosis. or RO. is a pressure driven method that separates salt from water by pumping it through a membrane. As higher efficiency membranes are made available at lower costs there are more and more RO plants. In fact many people have RO systems in their homes which operate on the same principles that major RO plants work on around the world.