Managed aquifer recharge (MAR)  meets growing water demands by replenishing groundwater aquifers with secondary water sources, such as reclaimed wastewater. Unfortunately, this process has been shown to trigger arsenic mobilization at some MAR sites. The mechanism behind this release is not well-understood and must be thoroughly characterized to establish safe MAR operations. In this study, arsenopyrite (FeAsS) dissolution was characterized for model wastewaters containing 10 mM sodium nitrate or chloride, and for a real wastewater sample. Interestingly, among these three systems, arsenic mobilization was highest in the chloride system under aerobic conditions. In addition, secondary mineral precipitation differed among the three systems, which can further affect arsenic mobilization. For example, iron(III) (hydr)oxide phase transformation was fastest in the chloride system, which can result in less arsenic sorption. Our new findings can help improve reactive transport models for MAR and develop strategies to mitigate arsenic contamination.

Water chemistry changes induced by managed aquifer recharge impact arsenopyrite dissolution and secondary mineral precipitation

251st National Meeting (2016)

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