DESTRUCTION OF AQUEOUS-PHASE TCE PLUME BY CONTROLLED-RELEASE KMNO4: A LARGE TEST CELL STUDY

A new semi-passive remedial technique using controlled-release KMnO4 (CRK) has been recently developed for long-term control of low-concentration aqueous-phase of chlorinated solvents. For pilot demonstration of destruction efficiency, a field-scale remediation experiment was performed using a major-scale groundwater field test facility (W x L x D = 4 m x 8 m x2 m) located in KRC, Korea. Based on the experimental and modeled data obtained for the CRK release and spreading mechanisms in the test cell, a dissolved TCE plume (velocity = 0.60 m/day, TCE concentration = 89 mg/L) was generated by circulating 1.22 tones of dilute TCE solution daily. Total of 110 emplaced, slow release forms were used for the CRK spreading test as the permeable reactive barrier system (W x L x D = 4 m x 2 m x 1.5 m). Effectively there were three discrete barriers of injection wells installed at 1-meter interval downstream normal to the contaminant plume. Variations in TCE concentrations were monitored at 70 monitoring points across the test cell downstream of the barrier system over 4 weeks of testing. The TCE concentrations diminished with distance, showing approximately 36 % destruction (56 ppb remaining) of TCE after the first barrier, 57 % destruction (39 ppb remaining) after the second barrier, and 67 % (29 ppb remaining) after the third barrier. Noticeably, groundwater velocity showed no temporal variations, suggesting negligible impact of reaction products, e.g., MnO2 solid, on the hydraulic conductivity of the porous medium. Results of this study suggested that the CRK scheme could provide a practical tool for long-term control of dissolved TCE plumes in groundwater. Utilizations of the CRK scheme for mitigation of plumes of other chlorinated solvents and reduced compounds may also be desired.