SOIL VAPOR EXTRACTION VERSUS BIOVENTING OF TOLUENE AND DECANE IN BENCH-SCALE SOIL COLUMNS

An experimental set-up with bench-scale soil columns was developed to simulate soil vapour extraction (SVE) and soil bioventing (SBV) under laboratory conditions. The distinction between SVE and SBV was made by using N-2 and CO2 free air as flushing gases, respectively. Semi-cont inuous monitoring of model oil hydrocarbons, CO2 and O-2 evolution in the soil gas using the gas chromatography, allowed the remediation res ults to be compared. Separation of SBV into evaporation and biodegrada tion processes, distinction of three independent phases for each proce ss, helped to get better insight in the basic aspects of both processe s and direct comparison with SVE. Soil-gas partitioning for toluene an d decane, together with monitored concentrations in soil vapours, were used to evaluate the kinetics of hydrocarbons removal from soil. Biod egradation and evaporation rates were determined for each phase to com pare SVE and SBV. In columns, each with ca. 4 kg of sandy soil, moistu re of 15% (w/w), and temperature 20 degrees C, about 4000 mg kg(-1) of toluene initially present in soil was reduced by 99% within 11 and 24 days of SBV and SVE, respectively, at the applied constant gas flow o f 40 cm(3) cm(-2) h(-1). The initial decane concentration of 400 mg kg (-1) decreased below 1 mg kg(-1) during SBV after 33 days, compared to 60 mg kg(-1) during SVE, within 36 days. SBV was shown as an appropri ate technology to treat VOCs (eg. toluene) a nd SVOCs (e.g. decane), i n contrast to SVE, with respect to remediation times a nd residual con centrations.