LABORATORY AND CONTROLLED FIELD EXPERIMENTS USING POTASSIUM-PERMANGANATE TO REMEDIATE TRICHLOROETHYLENE AND PERCHLOROETHYLENE DNAPLS IN POROUS-MEDIA

Few proven technologies exist that may be used to treat dense non-aque ous phase liquid (DNAPL) contaminants. In-situ chemical flushing is a proposed technology which consists of flushing DNAPL source zones with a reactive solution to degrade the contaminant mass below ground. A l aboratory and controlled field experimental program was conducted to a ssess the potential of potassium permanganate (KMnO4) as a reagent for in-situ DNAPL remediation. The results of laboratory experiments indi cated that two common DNAPL contaminants, perchloroethylene (PCE) and trichloroethylene (TCE), were rapidly degraded to chloride and carbon dioxide. Column experiments, using residual PCE flushed with oxidant c oncentrations as high as 10 g L-1, indicated that chloride could be us ed as a reaction tracer. From the chloride data, it appeared that the rate of PCE removal from the columns was a complex process dependent u pon the kinetics of both dissolution and oxidation. Two experimental a pplications of in-situ oxidation were conducted in the Borden aquifer isolated within a 7.5 m(3) double sheet-pile cell. The cell was fitted with injection and recovery wells through which aqueous solutions of KMnO4 were flushed to oxidize solvent source zones in situ. In the ini tial experiment, flushing of a 1 L PCE residual source with 10 g L-1 K MnO4 at total flow rates of up to 100 L per day, completely removed th e source within 120 days. A second experiment, using an 8 L mixture of PCE and TCE slowly allowed to infiltrate into the cell, was conducted using a system to recycle the oxidant. The oxidant was added at 10 g L-1 with a flow of approximately 50 L per day. After 290 days of flush ing, it was concluded from the monitoring data that 62% of the initial source (as equivalent chloride mass) had been oxidized and it was evi dent that oxidation was continuing in the upper third of the cell. The se experiments have suggested that the effectiveness of in-situ chemic al oxidation will depend primarily upon the distribution of the DNAPL in the subsurface and its effects upon dissolution. In both experiment s, spatial variability of chloride measurements appeared to reflect bo th the DNAPL location and distribution. (C) 1998 Elsevier Science B.V.