Comparison of anion exchange resins and aluminum-based coagulants for natural organic matter (NOM) removal and disinfection by-product (DBP) formation

Abstract

Anion exchange resins (AERs) were compared with aluminum-based coagulants for reducing disinfection by-product (DBP) precursor concentrations from a source water collected in northeast Ohio, USA. Three AERs (IRA-910, IRA-958, and MIEX) were evaluated to determine which resin would remove the most natural organic matter (NOM) and moieties responsible for DBP formation. All the AERs were found to be highly proficient at NOM removal specifically the moieties that absorb UV254 (i.e., chromophores) over 75 min of contact time; however, MIEX removed NOM at a faster rate than IRA-910 and IRA-958 resins. Enhanced coagulation was effective at removing approximately 35% of the NOM and 40–60% of the chromophores and fluorophores (i.e., excitation–emission matrix pairs A and C). DBP formation was determined as a function of pH for the different NOM removal processes. MIEX treatment resulted in significant reduction in DBP concentrations when compared to chlorinating the raw source water. MIEX generally out-performed enhanced coagulation for reducing DBP formation. However, alum was found to remove more NOM and resulted in less DBPs compared to aluminum chlorohydrate. This could impact water utilities trying to balance the health effects due to DBP exposure verses chemical/sludge management costs.