SOIL HEATING FOR ENHANCED REMEDIATION OF CHLORINATED SOLVENTS - A LABORATORY STUDY ON RESISTIVE HEATING AND VAPOR EXTRACTION IN A SILTY, LOW-PERMEABLE SOIL CONTAMINATED WITH TRICHLOROETHYLENE

Thermally enhanced remediation of trichloroethylene (TCE) from a 50 cm deep silty soil was demonstrated in a hive-dimensional laboratory tan k. Volatilized TCE was captured by vapor extraction in an overlaying c oarse sand layer. Soil vapor extraction was first tested alone at 23 d egrees C, showing very little efficiency due to the low-permeable laye r and an estimated cleanup time of more than 1 year. By injecting elec tric current, the temperature was increased to 85 and 100 degrees C in steps, and the fluxes of TCE increased by factors of 2.6 and 19, resp ectively. After 37 days of heating, the mass of TCE in the soil was re duced from 35 to 0.072 g, corresponding to 99.8% mass removal. Average soil TCE concentrations were reduced from 273 to 0.6 mg/kg. Steam pro duction by boiling of pore water and a 9-fold increase in the Henry's law constant of TCE were identified as the major mechanisms for overco ming mass-transfer limitations. The silty soil did not dry out due to water addition at the current electrodes, which is promising for the u se of thermal enhancements for remediation of water-saturated clay lay ers and in shallow groundwater. In-situ thermal cleanups can be done i n a few months, at costs typically below $100/m(3), and with very high removal efficiency for volatile and semivolatile organics.