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.

Removal of Dissolved Organic Matter by Magnetic Ion Exchange Resin

“…Reduction in UVA254 followed a similar trend as DOC removal for MIEX resin and alum coagulation [29]. Many subsequent researchers have shown similar results of high-DOC and UVA254 removal by MIEX resin [18,23,[30][31][32][33][34][35][36][37]. For example, Boyer and Singer showed greater removals of DOC and UVA254 by MIEX resin than alum coagulation across four different raw waters with the extent of removal increasing as the specific UVA254 (SUVA254) of the raw water increased from 2.0 to 3.8 L/mg·m [31].…”

“…Chlorination of water samples following MIEX treatment typically show high reductions in THMs and HAAs [29] and greater reductions in THMs than HAAs than coagulation [29,37]. For example, Singer and Bilyk showed THM reductions of 71-84 % by MIEX treatment of several different drinking water sources and similar reductions in HAAs as THMs [6].…”

“…It is important to note that the previous results apply to mixing times on the order of hours to days. At short mixing times on the order of minutes, MIEX resin shows a faster rate of DOC removal than conventional anion exchange resins [33,37]. MIEX resin was compared with six other commercially available strong-base anion exchange resins, which are marketed for organics removal, and showed faster and greater reductions in UVA254 from 5 to 30 min [12•].…”

Evaluating Options for Regenerant Brine Reuse in Magnetic Ion Exchange Systems

“…Though coagulant salts largely remain the mainstream method of DOC removal, anion exchange resins are a promising alternative (Crafton et al ). At the typical pH of most natural waters, hydroxyl and carboxylic acid functional groups tend to deprotonate.…”