Abstract
The Water Works Law requires water suppliers to monitor tap water quality periodically to make sure that the water meets the Drinking Water Quality Standards (DWQSs). In addition to DWQSs, Ministry of Health, Labour and Welfare provides Complementary Items, etc. for water suppliers to make sure the water quality in higher level by inspecting each item. The conformity to DWQSs, etc. is almost perfect, but there are still a few points where water quality does not meet DWQSs concerning to lead, bromate, etc. In order to reduce odorous substances to provide higher quality water, the DWQSs of geosmin and 2-methylisoborneol(2-MIB) were introduced in 2003 in Japan.
Water suppliers have been taking emergency measures against the outbreaks of musty odor in water sources. However, the tap water quality is still having odor and taste issue in some areas unfortunately. Though the number of affected people was over 20 million at worst in 1990, it is being about 3 million recently. Some water suppliers have installed advanced drinking water treatment process.
