Meeting California's Hexavalent Chromium MCL Using Strong Base Anion Exchange Resin

Abstract

The use of five strong base anion exchange resins to treat three potable groundwater sources to meet the new California maximum contaminant level (MCL) for hexavalent chromium (10 μg/L) was investigated. Depending on the resin used, bed volumes treated before breakthrough of total chromium (to 8 μg/L) ranged from approximately 13,800 to 26,400. At the point of resin exhaustion, uptake of total chromium (meq/L) accounted for less than 1% of the exchange capacity reported by resin vendors, whereas the uptake of sulfate accounted for 54–76%. Reusing the brine nine times produced a tenfold reduction in the volume of spent brine requiring ultimate disposal without significantly impairing resin performance. Chromium breakthrough profiles were relatively insensitive to a change in empty bed contact time (0.75 and 2.25 min) and hydraulic loading rates (8–55 mL/min‐cm2, 1.96–13.5 gpm/sf).