An electrokinetic/Fe0 permeable reactive barrier system for the treatment of nitrate-contaminated subsurface soils

Effective nitrate removal by Fe0 permeable reactive barriers (Fe0 PRB) has been recognized as a challenging task because the iron corrosion product foamed on Fe0 hinders effective electron transfer from Fe0 to surface-bound nitrate. The objectives of this study were (i) to demonstrate the effectiveness of an electrokinetic/Fe0 PRB system for remediating nitrate-contaminated low permeability soils using a bench-scale system and (ii) to deepen the understanding of the behavior and fate of nitrate in the system. Bench-scale laboratory experiments were designed to investigate the influence of the Fe0 content in the permeable reactive barrier, the pH in the anode well, and the applied voltage on remediation efficiency. The experimental results showed that the major reaction product of nitrate reduction by Fe0 was ammonium and that nitrate reduction efficiency was significantly influenced by the variables investigated in this study. Nitrate reduction efficiency was enhanced by either increasing the Fe0 content in the Fe0 reactive barrier or decreasing the initial anode pH. However, nitrate reduction efficiency was reduced by increasing the applied voltage from 10 V to 40 V due to the insufficient reaction time during nitrate migration through the Fe0 PRB. For all experimental conditions, nearly all nitrate nitrogen was recovered in either anode or cathode wells as nitrate or ammonium within 100 h, demonstrating the effectiveness of the system for remediating nitrate-contaminated subsurface soils.

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► An electrokinetic/Fe0 PRB system was applied for nitrate-contaminated subsurface soils.
► Fe0 PRB reduced nitrate into ammonium ion.
► The effect of operating parameters controlling reduction efficiency was discussed.
► Experimental data demonstrated the effectiveness of the electrokinetic/Fe0 PRB system.