|Salt removal could help U.S. water supply|
|Thu Apr 24 23:08:14 UTC 2008|
WASHINGTON (Reuters) - It may be possible to remove salt from more water to boost the U.S. fresh water supply, but additional studies need to be done to assess the environmental effects of doing so, a panel said on Wednesday.
U.S. capacity to desalinate water grew by around 40 percent between 2000 and 2005, and plants now exist in every state, the National Research Council panel reported.
Most use reverse osmosis, which pushes water through a membrane to separate out most salts. But it is expensive, uses a great deal of energy and its effects on the environment are unclear, the panel of engineers and other experts found.
The Earth is covered in water, but more than 97 percent of it is seawater or brackish groundwater and cannot be drunk or used for irrigation.
"Uncertainties about desalination's environmental impacts are currently a significant barrier to its wider use, and research on these effects -- and ways to lessen them -- should be the top priority," said Amy Zander, an engineering professor at Clarkson University in Potsdam, New York, who chaired the panel.
"Finding ways to lower costs should also be an objective. A coordinated research effort dedicated to these goals could make desalination a more practical option for some communities facing water shortages," she said in a statement.
Seawater reverse osmosis, which uses membranes to filter out the salt, uses about 10 times more energy than traditional treatment of surface water, according to the report.
It may be possible to make the process more energy-efficient by making the membranes more permeable, the committee said. A method called thermal desalination is another possibility.
The independent, advisory National Research Council, part of the National Academies of Science, was asked to look into the matter by the U.S. Environmental Protection Agency and the U.S. Bureau of Reclamation.
Desalination may be less environmentally harmful than many other ways to supplement water -- such as diverting freshwater from sensitive ecosystems, the report said.
But researchers should find out whether fish and other creatures get trapped in saltwater intake systems and what the effects are of disposing of the salt concentrate created by desalination, it said.
The report recommended that federal research and development on desalination be overseen by the White House Office of Science and Technology Policy and funded at current levels of about $25 million a year.
Federal research on desalination lacks an overall strategic direction, and the majority of research was left to the private sector, it said.