The responsibilities of the city of Osaka on revised Drinking Water Quality Standards by the Ministry of Health and Welfare in Japan

Ministry of Health and Welfare in Japan revised Drinking Water Quality Standards in 1992 to keep up with the change of industrial activities, lifestyle and increasing concern about disinfection by-products (DBPs). To respond to the new standards, Osaka Municipal Water Works Bureau (OMWW) reviewed the entire water supply system. In regard to water examination system, some simultaneous analysis instruments were introduced and joint monitoring system of water source with nine water utilities was established. In water purification plant, pH was increased to 7.5 which is a target value of the new standards. It was found that increase of pH value could reduce an elution of lead from lead service pipes; Advanced water treatment will be introduced to control musty odour and DBPs. On the other hand, direct connection water service system for high rise buildings was investigated to prevent deterioration of water quality in a tank. As a result of that, a part of high rise buildings were supplied water with direct connection water supply system. Tap water in the City of Osaka can meet the new standards perfectly by these measures.