Influence of Flocculant Aids and NOM Characteristics on the Removal of DBP Precursors During Enhanced Coagulation

摘要

In this study, two factors potentially influencing the removal of disinfection by-productprecursors during enhanced coagulation were examined: seasonal changes in natural organicmatter (NOM) characteristics and the addition of flocculant aids. Little variation in UV254,organic matter molecular weight, or dissolved organic carbon (DOC) concentration was observedover the course of one year for two Ohio drinking water reservoirs. Subsequently, the dosage offerric chloride required to meet United States Environmental Protection Agency (USEPA)enhanced coagulation requirements varied little as well. The addition of flocculant aids had apositive 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 dependedon the charge density of the polymer, with high charge density cationic polymers having thegreatest influence and nonionic flocculant aids having relatively little effect. It was alsoobserved that cationic flocculant aids were significantly more effective at removing the UVabsorbingfraction of Aldrich humic acid in synthetic source water as compared to the UVabsorbingfraction of the natural waters examined. While flocculant aids enhanced UV_(254)removal during ferric chloride coagulation, addition of these polymers did not reduce dissolvedorganic carbon.