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Even though Japan has mean annual precipitation of 1,714 mm and hundreds of dams and reservoirs constructed, frequent and severe droughtshave occurred in wide regions of the country. Because of rapid economic growth and concentrations of population in urban areas, water demands in large cities have stressed reliability of water supply systems and necessitated the development of new water resources with considerable economic and environmental costs. To alleviate these situations, wastewater reclamation and reuse have been implemented widely in major cities. This paper summarizes the current status of water reuse in Japan and discusses dominant uses of reclaimed water, emphasizing non-potable urban applications such as toilet flushing, industrial reuse, and environmental water. [ABSTRACT FROM AUTHOR]

Water reclamation and reuse provides a unique and viable opportunity to augment traditional water supplies. As a multi-disciplined and important element of water resources development and management, water reuse can help to close the loop between water supply and wastewater disposal. Effective water reuse requires integration of water and reclaimed water supply functions. The successful development of this dependable water resource depends upon close examination and synthesis of elements from infrastructure and facilities planning, wastewater treatment plant siting, treatment process reliability, economic and financial analyses, and water utility management. In this paper, fundamental concepts of water reuse are discussed including definitions, historical developments, the role of water recycling in the hydrologic cycle, categories of water reuse, water quality criteria and regulatory requirements, and technological innovations for the safe use of reclaimed water. The paper emphasizes the integration of this alternative water supply into water resources planning, and the emergence of modern water reclamation and reuse practices from wastewater to reclaimed water to repurified water.