This study aimed to evaluate the efficacy, practicality and sustainability of a combined approach based on solvent extraction and biodegradation to remediate the soils contaminated with high levels of weathered petroleum hydrocarbons. The soils used in this study were obtained from the Shengli Oilfield in China, which had a long history of contamination with high concentrations of petroleum hydrocarbons. The contaminated soils were washed using a composite organic solvent consisting of hexane and pentane （4：1, v/v） and then bioremediated in microcosms which were bioaugmentated with Bacillus subtilis FQ06 strains and/or rhamnolipid. The optimal solvent extraction conditions were determined as extraction for 20 min at 25 ~C with solvent-soil ratio of 6：1 （v/w）. On this basis, total petroleum hydrocarbon was decreased from 140000 to 14000 mg kg-1, which was further reduced to 〈 4000 mg kg-1 by subsequent bioremediatton for 132 d. Sustainability assessment of this integrated technology showed its good performance for both short- and long-term effectiveness. Overall the results encouraged its application for remediating contaminated sites especially with high concentration weathered hydrocarbons.
The liquid–solid countercurrent fluidization process in an extraction column was numerically simulated based on the particle trajectory model of Eulerian–Lagrangian method. The simulation approach was validated by previous experiments. A power function correlation was proposed for dimensionless slip velocity Uslip/Utand hold-up fraction φ, and the operational zone in the countercurrent fluidization was determined. Simultaneous countercurrent fluidization of particles with different diameters was also simulated. The comparison shows that the simulation results are consistent with the calculation values from the multi-particle free sedimentation model based on noninterference assumption, verifying the reliability of the approach in present work.
This study aims to investigate methyl tert-butyl ether(MTBE) dissolution in saturated porous media.A series of1 D column experiments were conducted in laboratory to obtain MTBE dissolution data with different groundwater velocity,initial MTBE saturation and grain size of porous medium,and in the presence of other nonaqueous liquids.Results indicate that higher groundwater velocity increases MTBE dissolution rate and higher initial MTBE saturation reduces effective permeability to slow MTBE dissolution rate.Smaller grain size medium gives higher MTBE dissolution rate because of higher permeability.The addition of trichloroethylene enhances MTBE dissolution,with an optimal mass ratio of 10:2,while the presence of p-xylene prolongs complete dissolution of MTBE.Mass transfer correlations are developed for MTBE dissolution rate based on the degree of MTBE saturation Sn.Mass transfer rate is characterized by Re' with a high exponent for 0.3000
