小笠原諸島の浄水場の処理過程におけるハロ酢酸とトリハロメタンの挙動

摘要

The behaviors of haloacetic acids (9 species) and trihalomethanes in the process of two water purification plant at Ogasawara Islands were investigated in August 2003 and January 2004. The total haloacetic acid formation poten tials (THAAFPs) in raw water were within the range of 178-356ug •l~(-1) with the concentrations in January exceeding those in August. The total trihalomethane formation potentials (TTHFPs) in raw water were within the range of 149-330μg •l~(-1) with the concentrations in August exceeding those in January. After coagulating sedimentation treatment, the THAAFPs and TTHMFPs were within the ranges of 33-59μg·l~(-1)and 44-86μg·l~(-1), respectively. The removal ratios of THAAFP tended to be higher than those of TTHMFP. THAAFP correlated closely with potassium perman ganate consumption and ultraviolet absorption (260nm). Following the coagulating sedimentation treatment, the use of chlorination caused a sudden decrease in the bromide ion concentration in water and generated trihalomethanes and haloacetic acids. Almost all of these concentrations gradually increased in tap water, with brominated haloacetic acids and trihalomethanes accounting for nearly all of the total haloacetic acids and total trihalomethanes.%小笠原諸島は，東京から南方へ約1，00Okm にある亜熱 帯性気候の国立公園の島々で，人が居住する父島と母島 に2ケ所の簡易水道の浄水場がある。これらの浄水場 は，島内の小さな川を堰き止めたダム湖の水を主な水道 水源としており，その水源水質は亜熱帯性気候特有の自 然環境により有機質が多く含まれている。1981年か ら1983年にかけて厚生省が実施した「全国の水道におけ るトリハロメタンの実態調査」の結果，父島と母島の簡 易水道のトリハロメタン濃度が制御目標値（0.1mg·l~(-1)） を超えた。