Pilot‐Scale Removal of Total and Hexavalent Chromium From Groundwater Using Stannous Chloride

Alternative processes for hexavalent chromium (Cr(VI)) removal from drinking water continue to be of interest for utilities despite the existence of several established technologies. Stannous chloride (SnCl 2 ) can reduce Cr(VI) to trivalent chromium, but research has been limited, especially related to the filterability of total chromium (Cr(T)) following reduction. At the pilot scale, SnCl 2 was tested over a range of doses in three groundwaters with naturally occurring Cr(VI) concentrations ranging from 0.020 to 0.090 mg/L. Stannous chloride was found to be effective as a reductant at doses <2 mg/L and contact times <5 min. A tin‐to‐chromium molar dose ratio of 4 was sufficient for reducing Cr(VI) to below 0.010 mg/L. Cartridge filters were unable to practically remove Cr(T) following reduction, but a standard‐design sand filter was able to remove Cr(T) to <0.010 mg/L.