Cost efficiency of subsurface remediation using soil vapor extraction and groundwater extraction

Abstract

The groundwater pollution due to volatile organochlorines like trichloroethylene and tetrachloroethylene has been a great environmental issue in Japan. The nation wide survey revealed on the basis of up to fifty-nine thousand samples collected until 1995 that 1.5% for trichloroethylene and 2.3% for tetrachloroethylene cannot meet the drinking water standard. In order to repair subsurface pollution and to establish the integrated procedure for cost-benefit remediation measure, physical remediation technologies of soil vapor extraction and groundwater extraction were applied to a study site contaminated with trichloroethylene. The results showed that the trichloroethylene amounts of 472 kg by soil vapor extraction and 1764 kg by groundwater extraction were removed during three-year operation. In addition experience with both technologies has demonstrated that the soil vapor extraction has been successful in removing 1 kg hr⁻¹ of trichloroethylene at the initial stage of remediation, which shows one order as high as the groundwater extraction. However, the removal rate due to soil vapor extraction declines much earlier than groundwater extraction, and consequently the removal rates of both technologies develop inversely with the progress of remediation. Such remediation behavior of technologies raised the relative cost for soil vapor extraction 15 times as high as groundwater extraction.