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 ground-waters 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.

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Hexavalent chromium (Cr(VI)) reduction using stannous chloride (SnCl 2 ) has emerged as a possible alternative to chromium treatment technologies such as strong base anion exchange. In an effort to target not only Cr(VI) reduction but, ultimately, total chromium (Cr(T)) removal, SnCl 2 addition followed by rapid sand filtration was tested at the pilot scale on a groundwater with a naturally occurring Cr(VI) concentration of 0.090 mg/L. A SnCl 2 dose of 1.5 mg/L, followed by filtration, was able to consistently remove Cr(T) to less than 0.010 mg/L following an initial ripening period, with limited head loss for 10 sequential 17-to 25-hr filter runs. Total tin and turbidity removal were similar, decreasing to below 0.050 mg/L and raw water levels, respectively. Analysis of filter sand following backwashes and three different material pipe segments that were exposed to unfiltered water dosed with SnCl 2 indicated the accumulation of Cr and Sn on surfaces, which remains a concern.

Ion exchange is effective for hexavalent chromium removal from drinking water sources, but non-target anions (i.e., arsenic, vanadium, and uranium) that co-occur in water sources must be assessed to inform,...