This book explores desalination technologies in the United States, which are increasingly used for municipal and industrial water supplies and reclamation of contaminated supplies. An 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.