Predicting hydrocarbon removal from thermally enhanced soil vapor extraction systems. 1. Laboratory studies

Conventional soil vapor extraction (SVE) systems have a limited effectiveness at removing semi-volatile chemicals from soil. Raising chemical vapor pressures by heating soil in-situ can decrease remediation time and help remove semi-volatile chemicals that otherwise would not be removed by conventional SVE. The increased compound removal rate that results from use of thermally enhanced SVE was investigated in laboratory studies. Increased soil temperatures (50-150 degrees C) increased both the rate of removal of the compounds studied and the range of compounds that were removed in column studies. The column studies indicated that if soil temperatures are raised enough to elevate the vapor pressure of a compound above 70 Pa, SVE will remove most of the compound from the soil. Thermally enhanced column study hydrocarbon removal rate constants were shown to have a definable relationship with vapor pressure. The relative removal rate constants also demonstrated an Arrhenius relationship with temperature. Laboratory studies can be used to develop these relationships and the results can be extrapolated within certain temperature ranges and compound types for a given soil.