processes, toilet flushing, and groundwater replenishing (EPA, 2004)." A similar description is: "Water Reuse, the use of reclaimed water from treated wastewater, has been a long-established reality in many (semi)arid countries and regions. It helps to alleviate water scarcity by supplementing limited freshwater resources." The water that is used as an input to the treatment and reuse processes can be from a variety of sources. Usually it is wastewater (domestic or municipal, industrial or agricultural wastewater) but it could also come from urban runoff. Overview Reclaimed water is water that is used more than one time before it passes back into the natural water cycle. Advances in municipal wastewater treatment technology allow communities to reuse water for many different purposes. The water is treated differently depending upon the source and use of the water and how it gets delivered. Driving forces The World Health Organization has recognized the following principal driving forces for municipal wastewater reuse: increasing water scarcity and stress, increasing populations and related food security issues, increasing environmental pollution from improper wastewater disposal, and increasing recognition of the resource value of wastewater, excreta and greywater. Water recycling and reuse is of increasing importance, not only in arid regions but also in cities and contaminated environments. Already, the groundwater aquifers that are used by over half of the world population are being over-drafted. Reuse will continue to increase as the world's population becomes increasingly urbanized and concentrated near coastlines, where local freshwater supplies are limited or are available only with large capital expenditure. Large quantities of freshwater can be saved by municipal wastewater reuse and recycling, reducing environmental pollution and improving carbon footprint. Reuse can be an alternative water supply option. Achieving more sustainable sanitation and wastewater management will require emphasis on actions linked to resource management, such as wastewater reuse or excreta reuse that will keep valuable resources available for productive uses. This in turn supports human wellbeing and broader sustainability. Potential benefits Water/wastewater reuse, as an alternative water source, can provide significant economic, social and environmental benefits, which are key motivators for implementing such reuse programs. These benefits include: For cities and households: Increased water availability (drinking water substitution – keep drinking water for drinking and reclaimed water for non-drinking use (i.e. industry, cleaning, irrigation, domestic uses, toilet flushing, etc.) For the environment: Reduced nutrient loads to receiving waters (i.e. rivers, canals and other surface water resources);