Distribution of Bromine/Chlorine-Containing Disinfection By-Products in Tap Water from Different Water Sources in the Hyogo Prefecture

摘要

An investigation was conducted to determine both the distribution and the concentration of 24 types of disinfection by-products (DBPs) formed by the chlorination of tap water during the water treatment process. The 24 DBPs consisted of 9 haloacetic acids (HAAs), 9 haloacetonitriles (HACNs), 4 trihalomethanes (THMs), chloral hydrate (CH) and formaldehyde (FA). The samples were collected from 8 different water sources in the Hyogo Prefecture. As a result of the field study, which was conducted 4 times in one year, 23 of the DBPs mentioned above [all except for tribromoacetonitrile (TBACN)] were detected in tap water. When the 24 DBPs are classified into their 5 main categories, it has previously been thought that THMs would form the highest concentration group. However, according to the results obtained in this study, the average values of the HAAs showed the highest at the various sampling points, followed by the THMs, HACNs, chloral hydrate and formaldehyde. The composition ratios of the bromine/ chlorine-containing DBPs in tap water from different water sources were compared. The ratio of chlorine-containing DBPs in tap water derived from surface water was higher than that in tap water derived from ground water. On the other hand, the ratio of the bromine-containing DBPs in tap water extracted from ground water was higher than that of tap water extracted from surface water. This tendency was observed equally for HAAs, HACNs and THMs. This phenomena was also supported by numerical results obtained using the bromine incorporation factor [n(Br)]. It was newly revealed that n(Br) is applicable to HAAs and HACNs in addition to THMs.