A Chemical Approach to Eliminating Arsenic Mobilization in the Subsurface During ASR Cycles

Chemical reactions between oxygenated recharge water and minerals in the receiving formation have caused mobilization of undesirable levels of metals, including arsenic, in several states.  Current mitigation processes involve deoxygenating water with membranes or selective ions at considerable cost.  This presentation will address a chemical method for reducing, or potentially eliminating the mobilization of arsenic induced by the injection of oxygenated water into an ASR storage zone bearing pyrite. The method is simply based on the implementation of Le Chatelier’s principle, and requires that the chemical nature of the injected water approach that of the native formation water so the chemical equilibrium can be maintained. Geochemical modeling results will also be provided to show that only one commonly available chemical is capable of accomplishing this task for pyrite bearing formations.