Investigation of trihalomethane formation after chlorine dioxide preoxidation followed by chlorination of natural organic matter

Chlorine dioxide (ClO2) is widely used as powerful oxidant to remove taste, odor and pathogenic microorganisms with chlorine during water treatment. In this study, the formation of trihalomethanes (THMs) was investigated in sequential ClO2 and chlorination processes. During the study, water samples were collected from Terkos Lake water (TLW) and Büyükçekmece Lake water (BLW) in Istanbul. To understand the relationship between the formation of THMs and the characteristics of natural organic matter (NOM), changes in the molecular weight (MW) of NOM fractions before and after ClO2 oxidation were characterized with the ultrafiltration technique. The NOM fraction with MW <1 kDa is the dominant fraction among all the fractionated water samples. ClO2 oxidized NOM to more hydrophilic and smaller organic fractions as seen in the NOM fraction with MWCO