Reduction in contaminant mass flux with induced oxide mineral precipitation in quasi-multidimensional systems

Dense non-aqueous-phase liquids (DNAPLs) are difficult to be removed from the highly heterogeneity aquifer. In situ chemical oxidation (ISCO) is one of the main DNAPL remediation technologies, but when using permanganate as oxidant to remediate the DNAPL in groundwater, the permeability within the DNAPL source area can be reduced due to the MnO₂ solid-phase formation. Hence, the study of the complex dynamic change in the DNAPL source zone is meaningful for improvement in the ISCO efficiency. A developed one-dimensional column experiment was used in this study. The columns used in the experiments were parallel-connected. Limited time interval and low-concentration permanganate flushing were applied in the experiments to mimic real field condition. It was found that the permeability within the DNAPL source zone was reduced only for short time due to the precipitation and flocculation of MnO₂ formed. The flow flux and mass flux within the DNAPL source zone decreased during permanganate oxidation while rebounded again after the oxidation. The experiment results illustrated that low concentration of permanganate oxidation can activate the DNAPL source area. Based on this phenomenon, an effective ISCO could be developed to remediate the source zone.