Abstract
Dissolved organic matter (DOM) in water samples obtained from raw water, reservoir, mountain stream and treated water in purification plants in the Ogasawara Islands, was fractionated into hydrophilic fractions, hydrophobic acids and hydrophobic neutrals. Hydrophilic fractions and hydrophobic acids of DOM were the main components of water samples from mountain streams, reservoirs and raw water in the Chichijima Island and Hahajima Island. The total trihalomethane formation potential (TTHMFP) and the contribution of each fraction were mostly in agreement with the total DOM and the rate of each fraction, respectively. The contribution of the hydrophobic acids fraction to the total haloacetic acid formation potential (THAAFP) was higher than that to TTHMFP. The rates or contributions of the hydrophilic fractions in DOM or TTHMFP/THAAFP were the highest, respectively, in activated carbon- and coagulation-sedimentation-treated water of the Chichijima Island, and coagulation-sedimentation-treated water of the Hahajima Island. It is thus suggested that a water treatment method for removing hydrophilic matter of DOM in raw water can effectively decrease the amount of DOM thus resulting in a decrease in the amount of disinfection by-products in treated water. It is presumed that the weight-average molecular weights of DOM in mountain stream water and raw water are both 1220∼1390 g·mol-1 , and it is indicated that DOM in raw water originates from such mountain streams flowing into a reservoir. It is also suggested that the weight-average molecular weights of DOM in treated water are reduced to 630∼970 g·mol-1 after water purification treatment.
