Abstract
Advanced water treatment-ozonation and activated carbon filtration-has been in operation at all utilities of Osaka Prefecture since July 1998 and Osaka City since March 2000. It was also introduced in one of the two utilities supplying water to the cities of Kobe, Nishinomia, Ashiya and Amagasaki. A blend of advanced treated surface water (ATSW) from Osaka Prefecture and their own conventionally treated water was supplied to the homes in almost all municipalities in Osaka Prefecture supplies.
We investigated total organic halogen (TOX) levels, as chlorination by-products, in 68 tap waters of 29 cities in Osaka Prefecture and its surrounding prefectures from July to August, 2000. No significant difference in TOX level of tap waters was observed between condominiums or apartments and detached houses. For ATSW, TOX were significantly increased from Osaka Prefectural purification plants to household taps, but the increase in TOX was not found in the case of Osaka City. TOX concentrations in the different type of tap waters were as follows: for ATSW, from 21.9 to 62.2μgCl/l, for a blend of ATSW and conventionally treated ground water (CTGW), from 11.5 to 57.1μgCl/l, for a blend of ATSW and conventionally treated surface water (CTSW), from 30 to 100μgCl/l, for a blend of CTGW and CTSW, from 40.9 to 106μgCl/l, for CTSW, from 32.8 to 171μgCl/l, for CTGW, 60.9μgCl/l. There was no difference in TOX levels of ATSW and a blend of ATSW and CTGW.
