The Water Science and Technology Board is undertaking a comprehensive study of the potential for water reclamation and reuse of municipal wastewater to expand and enhance the nation's available water supply alternatives. This broad study will consider a wide range of uses, including drinking water, non-potable urban uses, irrigation, industrial process water, groundwater recharge, and water for environmental purposes. The study will consider technical, economic, institutional, and social challenges to increased adoption of water reuse, and it will provide practical guidance to decision makers evaluating their water supply alternatives. The first phase of the study was a planning phase to guide the remainder of the study.In Phase I of the study, the NRC committee:• gathered relevant background information;• held one meeting to receive briefings, and • agreed upon a work plan that would support execution of the study on water reclamation and reuse (described below as Phase II). Phase IIIn Phase II of the study, now underway, the committee will consider a wide range of uses, including drinking water, non-potable urban uses, irrigation, industrial process water, groundwater recharge, and water for environmental purposes. Phase II of the study is expected to address the following issues and questions and result in a report of the study:1. Contributing to the nation's water supplies. What are the potential benefits of expanded water reuse and reclamation? How much municipal wastewater effluent is produced in the United States, what is its' quality, and where is it currently discharged? What is the suitability--in terms of water quality and quantity--of processed wastewaters for various purposes, including drinking water, non-potable urban uses, irrigation, industrial processes, groundwater recharge, and environmental restoration? 2. Assessing the state of technology. What is the current state-of-the-technology in wastewater treatment and production of reclaimed water? How do available treatment technologies compare in terms of treatment performance (e.g., nutrient control, contaminant control, pathogen removal), cost, energy use, and environmental impacts? What are the current technology challenges and limitations? What are the infrastructure requirements of water reuse for various purposes? 3. Assessing risks. What are the human health risks of using reclaimed water for various purposes, including indirect potable reuse? What are the risks of using reclaimed water for environmental purposes? How effective are monitoring, control systems, and the existing regulatory framework in assuring the safety and reliability of wastewater reclamation practices?4. Costs. How do the costs (including environmental costs, such as energy use and greenhouse gas emissions) and benefits of water reclamation and reuse generally compare with other supply alternatives, such as seawater desalination and non-technical options such as water conservation or market transfers of water? 5. Barriers to implementation. What implementation issues (e.g., public acceptance, regulatory, financial, institutional, water rights) limit the applicability of water reuse to help meet the nation's water needs and what, if appropriate, are means to overcome these challenges? Based on a consideration of case studies, what are the key social and technical factors associated with successful water reuse projects and favorable public attitudes toward water reuse? Conversely, what are the key factors that have led to the rejection of some water reuse projects? 6. Research needs. What research is needed to advance the nation’s safe, reliable, and cost-effective reuse of municipal wastewater where traditional sources of water are inadequate? What are appropriate roles for governmental and non-governmental entities?The study is sponsored by the U.S. Environmental Protection Agency, the National Science Foundation, the National Water Research Institute, the Centers for Disease Control, the Water Research Foundation, Orange County Water District, Orange County Sanitation District, Los Angeles Department of Water and Power, Irvine Ranch Water District, West Basin Water District, Inland Empire Utilities Agency, Metropolitan Water District of Southern California, Los Angeles County Sanitation District, and the Monterey Regional Water Pollution Control Agency.The approximate start date for the project is May 29, 2008 with a Phase I duration of 7 months.The expected duration of Phase II is 33 months, with the final report anticipated by December 2011.