EFFICACY OF STRATEGIES FOR THE IN SITU OXIDATION OF CHLORINATED SOLVENTS USING POTASSIUM PERMANGANATE

Oxidation schemes are increasingly being used for treating DNAPLs, particularly the common chlorinated solvents such as trichloroethylene and tetrachloroethylene. One of the most popular oxidants is KMnO4. Permanganate (MnO4-) treatment is attractive due to the rapid rates of reaction with chlorinated compounds and the relatively low cost. The best strategy to implement oxidation schemes, however, remains to be determined. This paper examines two approaches for using MnO4- to remove chlorinated solvents from soil and groundwater. One approach is source zone flooding, where injection and withdrawal wells are placed to facilitate flooding of a DNAPL source with MnO4-. Results from our 3-D tank experiment indicated that the DNAPL destruction with MnO4- decreased with time due to the formation of low-permeability MnO2 precipitants in the source zone and around the TCE plume. This experiment highlights the problem of plugging that impact flooding schemes. An alternative approach is a semi-passive DNAPL treatment using emplaced solid KMnO4 as reactive materials. This scheme takes advantage of the tendency for reaction products to reduce the permeability of the treatment zone, which will control the dissolution of the solid and maintain MnO4- in contact with the DNAPL. In a series of 2-D column experiments we characterized MnO2 distributions, and measured aqueous concentrations, and hydraulic properties. Results indicated that the formation of solid MnO2 considerably slowed the dissolution and removal of the KMnO4 solids emplaced in the contaminated zone. These results suggest that it may be possible to use the tendency for plugging to control the dissolution rate of KMnO4 in a manner that will maximize the contact times with the organic contaminant. These results support the continued investigation of semi-passive treatment scheme for the remediation of groundwater contaminated with DNAPL.