Molecular Weight Effects on THM Control by Coagulation and Adsorption

Abstract

Three natural waters containing substantial levels of dissolved organic carbon were studied to assess the removal of aquatic organic matter and humic substances by coagulation and adsorption. As a general trend, alum coagulation was found to remove higher molecular weight material, while activated carbon adsorption was observed to remove a broader molecular weight spectrum of material. This apparent selective removal of certain molecular weight ranges by a given treatment process suggests that an appropriate process can be selected to specifically remove certain organic/humic fractions that are most reactive in producing trihalomethanes upon chlorination. Moreover, if a greater degree of removal is required, the conjunctive use of coagulation and adsorption may be the best strategy for meeting this objective.