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Friday, September 2, 2011

Desalination: Technologies, Use, and Congressional Issues

Nicole T. Carter
Specialist in Natural Resources Policy

In the United States, desalination technologies are increasingly used for municipal and industrial water supplies and reclamation of contaminated supplies. At issue for Congress is the federal role in desalination research, demonstration and full-scale facilities, and regulatory requirements. Constraints on wider adoption include financial, environmental, regulatory issues and concerns.

Desalination processes generally treat seawater or brackish water to produce a stream of freshwater, and a separate, saltier stream of water that has to be disposed (often called waste concentrate). Its attractions include creation of a new freshwater source from otherwise unusable waters, and its independence from precipitation, runoff, storage, and recharge. Many states (most notably Florida, California, and Texas) and cities are actively researching and investigating the feasibility of large-scale desalination plants for municipal water supplies. Coastal communities are increasingly considering desalinating seawater or estuarine water, while interior communities are looking to brackish aquifers. Some communities and industries are opting to treat contaminated water supplies with desalination technologies (e.g., membrane separation) to meet disposal requirements or to reuse the water (e.g., saline waters from oil and gas development). Desalination also is used for obtaining high-quality water for industrial processes.

Desalination and its applications, however, come with risks and concerns. Although the costs of desalination dropped steadily in recent decades, making desalinated water more competitive with other supply augmentation options, the declining trend may not continue if energy costs rise. This creates a cost uncertainty for those contemplating desalination investments. Electricity expenses vary from one-third to one-half of the operating cost of many desalination facilities, and the energy intensity of desalination raises concerns about the greenhouse gas emissions emitted. Current desalination processes are already operating close to the theoretical minimum energy required. Therefore, significant improvements in facility-level energy efficiency are more likely to come from more energy efficient pretreatment of water before entering the desalination process and co-location with other facilities, such as power plants. Substantial uncertainty also remains about the technology’s environmental impacts, in particular management of the saline waste concentrate and the effect of surface water intake facilities on aquatic organisms. Moreover, there are few federal health and environmental guidelines, regulations, and policies specific to desalination as a municipal water supply source. This creates uncertainty regarding the cost and time required for regulatory compliance. Research and public education may help to resolve some uncertainties, mitigate impacts, reduce the costs, and improve public understanding.

To date, the federal government has been involved primarily in desalination research and development (including for military applications), some demonstration projects, and select fullscale facilities. For the most part, local governments, sometimes with state-level involvement, are responsible for planning, testing, building, and operating desalination facilities, similar to their responsibility for freshwater treatment for municipal drinking water supplies. In the 112th Congress, H.R. 2664, Reauthorization of Water Desalination Act of 2011, would reauthorize a Department of the Interior program (expiring in 2011) carried out by the Bureau of Reclamation for desalination demonstration and outreach. Bills in the 111th Congress (e.g., H.R. 88, H.R. 469, H.R. 1145, S. 1462, S. 1731, S. 1733, and P.L. 111-11) represented a range of federal authorizations for desalination research and its coordination, demonstration and full-scale facilities, and planning and financing. While interest in desalination persists among some Members, efforts to expand federal activities and investment may face greater challenges in the near term due to the domestic fiscal climate and differing views on federal roles and priorities.

Date of Report: August 15, 2011
Number of Pages: 14
Order Number: R40477
Price: $29.95

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