Advances in Wastewater Reclamation and Reuse Technologies: Selected Case Study Projects in Japan

Japan has been developing non-potable water reuse systems mainly for urban applications such as toilet flushing, urban stream water augmentation, and landscape irrigation. Recently in Japan, reclaimed water has attracted attention not only as water resource but also a heat and energy source. Because sewage temperature is more stable than atmospheric temperature, the efficiency of heat pump systems improves when reclaimed water is used for the heat source/sink than when air is used for. In addition, a cogeneration system applying a biogas power generator is considered as an effective option that can produce electricity and heat energy from food waste and excessive sludge of biological treatment processes. Two commercial buildings in Osaka have installed advanced environmental technologies such as an onsite water reclamation system, a biogas power generation system, and a heat recovering system from reclaimed water. By using reclaimed water as water resource, as well as heat and energy source, these buildings can successfully save the amount of tap water and energy consumption required for hot water supply and heating and cooling systems in the facilities. This chapter describes the two case study projects in Osaka.