Book excerpt: In communities all around the world, water supplies are coming under increasing pressure as population growth, climate change, pollution, and changes in land use affect water quantity and quality. To address existing and anticipated water shortages, many communities are working to increase water conservation and are seeking alternative sources of water. Water reuse- the sue of treated wastewater, or "reclaimed" water, for beneficial purposes such as drinking, irrigation, or industrial uses- is one option that has helped some communities significantly expand their water supplies. Understanding Water Reuse summarizes the main findings of the National Research Council report Water Reuse: Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater. The report provides an overview of the options and outlook for water reuse in the United States, discusses water treatment technologies and potential uses of reclaimed water, and presents a new analysis that compares the risks of drinking reclaimed water to those of drinking water from traditional sources.