Pilot-scale studies of hexavalent chromium removal from drinking water

The goal of this research was the initial evaluation of several pilot-scale treatment technologies for hexavalent chromium removal to < 5 mu g/L (i.e., 95% removal). A major focus was to assess manufacturer-provided pilot systems with media that were effective in bench-scale studies as well as technologies that were promising but could not be appropriately tested at bench scale. The technologies tested included ion exchange systems (i.e., column strong-base and weak-base anion exchange and reactor-based strong-base anion exchange), a reduction/ filtration unit using sodium sulfite, and proprietary adsorptive media systems (zeolite and granular activated carbon). In vendor-independent tests, reduction with ferrous sulfate, coagulation, and filtration was also evaluated. Regeneration efficiency was determined for the best-performing strong-base anion exchange resin, including the effect of recycling brine to minimize residuals. Technologies able to consistently treat to concentrations < 5 mu g/L included column strong-base anion exchange, weak-base anion exchange, and reduction-coagulation-filtration using ferrous sulfate.