Eliminating Arsenic Mobilization in the Subsurface During ASR Cycles

Aquifer Storage and Recovery wells have experienced problems with elevated arsenic levels in recovered water in several states.  Chemical reactions between oxygenated recharge water and minerals in the receiving formation have resulted in the mobilization of undesirable levels of trace metals including arsenic.  Current mitigation processes involve deoxygenating water prior to recharge with membranes or catalysts at considerable cost. 

This presentation will address a method for preventing the mobilization of arsenic by adding a simple sulfide compound to the injected water at ppm levels.  The sulfide scavenges free oxygen and other oxidants from the recharge water and acts to prevent pyrite dissolution.  The recovered water has a minimal increase in sulfates and very low levels of arsenic.

A demonstration project is underway on an ASR well in Deland, Florida.  The field data demonstrate that the process reduces arsenic levels and maintains them well below drinking water standards during full scale ASR cycles at a cost that is substantially below other deoxygenation methods.