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Desalination Can Boost U.S. Water Supplies, But Research Needed to Understand Environmental Impacts, Lower Costs
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From the National Academies National Research Council:
Washington, D.C. -- Recent advances in technology have made removing salt from seawater and groundwater a realistic option for increasing water supplies in some parts of the U.S., and desalination will likely have a niche in meeting the nation's future water needs, says a new report from the National Research Council. However, a coordinated research effort with steady funding is required to better understand and minimize desalination's environmental impacts -- and find ways to further lower its costs and energy use.
Over 97 percent of the Earth's water -- seawater and brackish groundwater -- is too salty to use for drinking water or agriculture. Interest in desalination has grown in the U.S. as some regions face water shortages and contention over existing freshwater supplies. Though desalination still generates less than 0.4 percent of the water used in the U.S., the nation's capacity to desalinate water grew by around 40 percent between 2000 and 2005, and plants now exist in every state. Most use a method called reverse osmosis, which pushes water through a membrane to separate out most of the salts.
The report recommends that federal R&D on desalination be planned and coordinated by the White House Office of Science and Technology Policy and funded at the level of existing desalination R&D programs -- approximately $25 million a year. Currently there is no overall strategic direction to federal research on desalination, which is conducted by many agencies with varying goals. It also depends heavily on earmarks, which are unsteady sources of funding; from 2006 to 2007, federal funds declined by nearly 60 percent. Meanwhile, the private sector appears to fund the majority of the nation's desalination research. Both the public and private sectors can contribute to the proposed research agenda, the report says.
Environmental Research Should Be Highest Priority
Substantial uncertainties remain about the environmental impacts of desalination, the report says. Limited studies suggest that desalination may be less environmentally harmful than many other ways to supplement water -- such as diverting freshwater from sensitive ecosystems -- but definitive conclusions cannot be made without further research.
Desalination also has raised concerns about greenhouse gases because it uses large amounts of energy. Seawater reverse osmosis uses 10 times more energy than traditional treatment of surface water, for example, and in most cases uses more energy than other ways of augmenting water supplies. Researchers should investigate ways to integrate alternative energy sources -- such as the sun, wind, or tides -- in order to lower emissions from desalination, the report says.
R&D Needed to Lower Costs, Energy Use
Recent improvements in technology have lowered desalination's costs and energy requirements, which used to be prohibitively high. Meanwhile, other ways to augment water supplies have grown more expensive, making desalination more competitive. Finding ways to further lower costs should be another goal of the research effort, the report says.
Developing cost-effective, environmentally sustainable ways to dispose of salt concentrate should be a priority. The cost of disposing of this waste varies widely by site and has generally risen. Inland plants, in particular, have few or no cost-effective and environmentally sustainable disposal methods.
Even if costs are lowered, the report notes, conserving water or transferring it from one use to another will in most cases remain a less expensive option than adding water through desalination or other methods.
The study was sponsored by the U.S. Bureau of Reclamation and U.S. Environmental Protection Agency. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter. The Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering.
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Copies of Desalination: A National Perspective are available from the National Academies Press at 202-334-3313 or 800-624-6242 or on the Web at http://www.nap.edu.