AWWA WQTC54996

In this study, two factors potentially influencing the removal of disinfection byproduct precursors during enhanced coagulation were examined: seasonal changes in natural organic matter (NOM) characteristics and the addition of flocculant aids. Little variation in UV254, organic matter molecular weight, or dissolved organic carbon (DOC) concentration was observed over the course of one year for two Ohio drinking water reservoirs. Subsequently, the dosage of ferric chloride required to meet United States Environmental Protection Agency (USEPA) enhanced coagulation requirements varied little as well. The addition of flocculant aids had a positive effect on the removal of the UV-absorbing NOM fraction during enhanced coagulation, at least at high polymer dosages (10 mg/L or greater). The influence of flocculant aids depended on the charge density of the polymer, with high charge density cationic polymers having the greatest influence and nonionic flocculant aids having relatively little effect. It was also observed that cationic flocculant aids were significantly more effective at removing the UV-absorbing fraction of Aldrich humic acid in synthetic source water as compared to the UV-absorbing fraction of the natural waters examined. While flocculant aids enhanced UV254 removal during ferric chloride coagulation, addition of these polymers did not reduce dissolved organic carbon. Includes 13 references, tables, figures.