We conducted a series of flow-through column experiments using aquifer sediment treated with zero valent iron (Fe-0) with or without active microbial sulfate reduction. The aim of this study was to investigate the stability of Zn removed by Fe-0 and impact of sulfate reducing bacteria (SRB). The leaching of Zn was assessed by flushing the aquifer in vertical glass columns with groundwater that was pre-treated with mixture of gases to simulate natural changes (pH and ORP) in subsurface environment (N-2 + CO2 for pH and N-2 + O-2 for ORP) along with a control (N-2 flushed). Zinc removed synergistically by Fe and SRBs was found to be more stable and did not leach from the aquifer sediment with pH or redox changes. We also observed that the Zn leaching in the aquifer treated only with Fe was more influenced by change in redox than by pH changes. These results were also confirmed by sequential metal extractions and scanning electron microscopy observations in the aquifer sediments. Mineral phases were predicted using geochemical modeling tool CHESS confirming that the metal removed in Fe-o + SRB conditions formed more stable precipitates and did not show any signs of leaching back to groundwater upon change in pH and redox conditions. (C) 2014 Elsevier B.V. All rights reserved.