Removal of Dissolved Organic Matter by Magnetic Ion Exchange Resin

This article provides a state-of-the-art review on the uses of magnetic ion exchange (MIEX) resin in drinking water and wastewater treatment, with emphasis on removal of dissolved organic matter (DOM) from drinking water and wastewater, regeneration efficiency, removal of inorganic and synthetic organic chemicals, comparison with other anion exchange resins, and integration with other physical-chemical processes. Through laboratory jar tests, pilot plant tests, and full-scale installations for a variety of drinking water sources, MIEX resin can achieve 30-80 % removal of dissolved organic carbon (DOC), which is often higher than alum or ferric coagulation. In addition, MIEX resin has been shown to remove hydrophilic, transphilic, and hydrophobic fractions of DOM and a wide range of molecular weight fractions of DOM. As a result, MIEX pretreatment results in substantial reductions in the formation of trihalomethanes and haloacetic acids upon chlorination. MIEX resin can achieve bromide removal in the range of 10-50 %, with higher bromide removal in waters with low DOC, low alkalinity, and low sulfate. However, there are commercially available anion exchange resins that are more selective for bromide than MIEX resin. MIEX resin has been investigated in combination with coagulation, activated carbon adsorption, membrane separation, lime softening, and ozonation. MIEX pretreatment has been shown to reduce downstream chemical requirements and improve the operation of downstream processes. This is most evident for coagulation and ozonation where the coagulant dose can be reduced by 50-75 % and the ozone concentration can be increased by 40-65 %. In general, MIEX pretreatment shows minor reductions in membrane fouling. Future research should continue to investigate the integration of MIEX treatment with other processes.