NRC Report - Desalination: A National Perspective
The National Research Council's Committee on Advancing Desalination Technology has just released its report, Desalination: A National Perspective.
You can read it free online, pay to download individual chapters or the whole report, or buy a hard copy.
Here is the NRC press release and an executive summary:
From the WWW site:
There has been an exponential increase in desalination capacity both globally and nationally since 1960, fueled in part by growing concern for local water scarcity and made possible to a great extent by a major federal investment for desalination research and development. Traditional sources of supply are increasingly expensive, unavailable, or controversial, but desalination technology offers the potential to substantially reduce water scarcity by converting the almost inexhaustible supply of seawater and the apparently vast quantities of brackish groundwater into new sources of freshwater.
Desalination assesses the state of the art in relevant desalination technologies, and factors such as cost and implementation challenges. It also describes reasonable long-term goals for advancing desalination technology, posits recommendations for action and research, estimates the funding necessary to support the proposed research agenda, and identifies appropriate roles for governmental and nongovernmental entities.
The press release notes some potential environmental consequences:
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.
One of the issues of concern is the unknown human health effects of boron, which often exceeds WHO health guidelines after single-pass reverse osmosis desalination. EPA has not established a maximum contaminant level (MCL) for boron because it doesn't occur in signifcant concentrations in surface and ground waters.
I remember hearing Rhodes Trussell speak of the boron issue at an NRC symposium four years ago. He was confident the boron problem would be overcome, but urged caution.
High levels of boron are often associated with thermal waters. The health effects are generally not known very welll. A Swiss colleague of mine, who works a lot in the geothermal systems of the Mediterranean, told me that there is anecdotal evidence that high levels of boron in drinking water can cause spontaneous abortions/miscarriages.
I am also concerned about the disposal of waste. See my earlier post on desalting ground water in the Albuquerque area.
Desalination is a promising technology to augment fresh water supplies, but much work needs to be done. And we must always be cognizant of the Law of Unintended Consequences.
“When one tugs at a single thing in nature, he finds it attached to the rest of the world." -- John Muir
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