Occurrence of Trihalomethanes in Tap Waters of Niigata Prefecture.

概要

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Trihalomethanes (THMs) in 26 tap waters of 20 cities in Niigata Prefecture were measured both in 1989 summer and in 1990 winter (February) . The maximum, minimum and average were 39.2 (ug/1), 0.9 and 18.0, respectively in 1989 summer, and 17.7, 0.8 and 7.7, respectively in 1990 winter. THMs levels were clearly classified according to raw water source, water purification method and chlorination point. The highest level of THMs was found in waters produced by the rapid sand filtration of surface water with pre-chlorination, followed by that with intermediateor post-chlorination, and the slow sand filtration of surface water or the direct supply of groundwater. The tap waters of Gosen City and Murakami City, which THMs were so low in quantity, were found to be polluted continuously with a small amount of organic solvents.<BR>The THMs in tap waters of Niigata City were also measured in the same season with the above (26 points in 1989 summer and 8 in 1990 winter. Waters were supplied by 5 water treatment plants) . The THMs in water supplys which sources were the Shinano River were higher than the Agano River. Different types of rapid sand filtration plants produced different amounts of THMs. Bromof orm was found exclusively in tap waters from the Agano River.
日本環境化学会の論文