Removal of mixed contaminants by Fe⁰-based biobarrier in flow-through columns using recycled waste materials

The present study investigated the reactivity and ability of permeable reactive barriers [zero-valent iron (ZVI)-barrier plus biobarrier) to remove various contaminants (Cd, As, Zn, Cu, Mn, Cr, NO₃^-, NH₄⁺, and COD_cr) from synthetic leachate. Two different reactive materials were used in this study, namely ZVI and autoclaved lightweight concrete (ALC). After 90 days of column operation, the contaminant profiles were determined along the length of the columns. The heavy metals were extensively removed in the bio-ALC and sequential barriers (ZVI plus bio-ALC), however the removal efficiencies for the heavy metals Zn and Cr in the ALC and bio-ALC barriers were comparatively low. Nitrate was completely removed (>99.9%) in the ALC, bio-ALC, and sequential barriers. More than 50% of the produced ammonium and organic materials were removed in the biologically reactive zone of the sequential barriers. The results of the present study suggest that sequential barriers are one of the best solutions for in situ remediation and that they can be applied to clean up the leachate released from landfills.