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Date: April 24, 2008
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FOR IMMEDIATE RELEASE
Desalination Can Boost
To Understand Environmental Impacts, Lower Costs
WASHINGTON -- 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.
"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 K. Zander, chair of the committee that wrote the report and professor at
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
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.
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.
Researchers should investigate the extent to which fish and other creatures get trapped in saltwater intake systems in various settings, and seek ways to mitigate this and other impacts. Studies also should examine the long-term ecological effects of disposing of the salt concentrate that remains after desalination in rivers or the sea, a common practice. In addition, environmental evaluations of new desalination plants should be conducted, including ecological monitoring before and after the plant starts operating. The results should be synthesized with existing data in a national assessment that can guide future decision making, the report says.
Desalination also has raised concerns about greenhouse gases because it uses large amounts of energy. Seawater reverse osmosis uses about 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.
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.
Making the membranes used in reverse osmosis more permeable could lower desalination's energy use and costs further, as can improving the pre-treatment of water to remove sediments that can hinder membranes' efficiency, the report says. Even with improved technologies, however, the energy used by reverse osmosis probably cannot be reduced more than 15 percent below current levels. Larger reductions in energy costs may be possible using other desalination methods that could be powered with low-grade heat left over from other industrial processes, which would otherwise go to waste. Thermal desalination is one such method, and it may be possible to develop other novel approaches.
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,
NATIONAL RESEARCH COUNCIL
Division on Earth and Life Studies
Water Science and Technology Board
Committee on Advancing Desalination Technology
Amy K. Zander (chair)
Professor and Director
Interdisciplinary Engineering and Management
Roberto C. Goizueta Professor of Environmental and Chemical Engineering,
Department of Chemical Engineering, and
Environmental Engineering Program
David H. Furukawa
Separation Consultants Inc.
Co-Founder and President
Pacific Institute for Studies in Development, Environment, and Security
Water Supply Program Director
Resource Projects Department
Kimberly L. Jones
Associate Professor of Civil Engineering
Department of Civil Engineering
Vice President of Water Technology
Project Manager and Senior Project Engineer
Water Consultants International
Henry J. Vaux Jr.
Professor Emeritus of Resource Economics
Judith S. Weis
Department of Biological Sciences
Warren W. Wood
John Hannah Professor of Integrative Studies
Department of Geological Sciences
RESEARCH COUNCIL STAFF
Stephanie E. Johnson