Hexavalent chromium removal through conventional filtration treatment processes

Abstract

A pilot-scale study was conducted to evaluate the efficacy of reduction/coagulation/filtration (RCF) integration into conventional filtration treatment processes for hexavalent chromium (CrVI) and total chromium removal from surface water. RCF was effective for CrVI and total chromium removals of > 99 and > 93%, respectively, from surface water spiked with 25 μg/L CrVI. However, longer filter ripening and higher headloss accumulation rates were observed. Increased aluminum sulfate (alum) and filter aid dosages were assessed to improve filter performance; alum slightly improved performance, while filter aid reduced performance. Increased chlorine contact time with low chlorine dosages enhanced iron-chromium floc formation and reduced filter ripening and headloss accumulation rates resulting in longer filter run times. CrVI removals decreased from > 99 to > 98% while total chromium removals increased to > 98%. These results demonstrate that RCF integration effectively decreased CrVI and total chromium in surface water while maintaining regulatory compliance. 2015