Performance of selected anion exchange resins for the treatment of a high DOC content surface water

Abstract

The objective of this study was first to compare the performance of four strong anion exchange resins (AERs) (MIEX ® from Orica Pty Ltd, DOWEX-11 ® and DOWEX-MSA ® from DOW chemical and IRA-938 ® from Rohm and Haas) for their application in drinking water treatment (natural organic matter (NOM), mineral anions (nitrate, sulfate and bromide) and pesticide removal) using bench-scale experimental procedures on a high DOC content surface water. The efficiency of MIEX ® for NOM and mineral anions removal was furthermore evaluated using bench-scale dose-response experiments on raw, clarified and post-ozonated waters. NOM removal was assessed using the measurement of dissolved organic carbon (DOC), UV absorbance at 254 nm (UV 254) and the use of high-performance size exclusion chromatography with UV (HPSEC/UV) and fluorescence detection (HPSEC/FLUO). The MIEX ® and IRA938 ® anionic resins exhibit a faster removal of NOM and mineral anions compared to the DOWEX11 ® and MSA ® AERs. All the resins were found to be very effective with similar performances after 30 to 45 min of contact time. As expected, only limited sorption of atrazine and isoproturon ( C 0=1 μg/L) occurred with MIEX ®, DOWEX11 ® and MSA ® AERs. MIEX ® resin proved to be very efficient in eliminating NOM of high-molecular weight but also a large part of the smallest UV absorbing organic compounds which were refractory to coagulation/flocculation treatment. Remaining DOC levels after 30 min of contact with MIEX ® were found similar in raw water, clarified water and even post-ozonated water implying no DOC benefit can be gained by employing conventional treatment prior to MIEX ® treatment. Removal of bromide (initial concentration 110 μg/L) was also observed and ranged from 30% to 65% for resin dose increasing from 2 to 8 mL/L.