Bioremediation Enhances the Pollutant Removal Efficiency of Soil Vapor Extraction (SVE) in Treating Petroleum Drilling Waste

Contamination due to improper disposal of oilfield drilling waste is a serious environmental problem all over the world. This study used bench-scale experimental columns to investigate the effectiveness of combining soil vapor extraction (SVE) with bioremediation (bioaugmentation plus biostimulation) in treating drilling waste from onshore oil wells. The drilling waste used in this study was heavily contaminated with a total petroleumhydrocarbon (TPH) concentration of 2.5 x 10(4) mg/kg. After 154 h of SVE operation, the TPH concentrations decreased by 4.7-23.6 %, and continuous SVE operation did not significantly reduce the concentration of residual contaminants. Then, microbial consortium and inorganic nutrients (urea and K2HPO4) were employed further to enhance bioremediation, and after 216 h of bioremediation and SVE, 70 % of the residual TPH was removed. Bioremediation enhanced the overall pollutant removal efficiency by fully degrading low volatile compounds and transforming them into more volatile compounds which were extracted by SVE. Results from GC-MS analysis corroborated TPH concentration data showing the occurrence of biotransformation during SVE and bioremediation treatment. Overall, this study demonstrates that SVE combined with bioremediation is an effective technique for handling petroleum drilling waste.