Injection of biosurfactant and chemical surfactant following hot water injection to enhance heavy oil recovery

This study investigates the potential of enhancing oil recovery from a Middle East heavy oil field via hot water injection followed by injection of a chemical surfactant and/or a biosurfactant produced by a Bacillus subtilis strain which was isolated from oil-contaminated soil.The results reveal that the biosurfactant and the chemical surfactant reduced the residual oil saturation after a hot water flood.Moreover,it was found that the performance of the biosurfactant increased by mixing it with the chemical surfactant.It is expected that the structure of the biosurfactant used in this study was changed when mixed with the chemical surfactant as a probable synergetic effect of biosurfactant-chemical surfactants was observed on enhancing oil recovery,when used as a mixture,rather than alone.This work proved that it is more feasible to inject the biosurfactant as a blend with the chemical surfactant,at the tertiary recovery stage.This might be attributed to the fact that in the secondary mode,improvement of the macroscopic sweep efficiency is important,whereas in the tertiary recovery mode,the microscopic sweep efficiency matters mainly and it is improved by the biosurfactantchemical surfactant mixture.Also as evidenced by this study,the biosurfactant worked better than the chemical surfactant in reducing the residual heavy oil saturation after a hot water flood.

Co-occurrence of per- and polyfluoroalkyl substances, heavy metals and polycyclic aromatic hydrocarbons and their composite impacts on microbial consortium in soil: A field study

This is the first study to report the co-occurrence of per-and polyfluoroalkyl substances(PFASs),heavy metals,and polycyclic aromatic hydrocarbons(PAHs)and their impacts on the native microbial consortium in soil due to the long-term exposure.The PFASs,heavy metals,and PAHs were detected in soil samples collected at 2–6 m below the ground surface at different sampling locations in a steel-making factory.The total concentrations of PFASs varied from 6.55 to 19.79 ng g^(-1),with perfluorooctane sulfonate(PFOS),perfluorobutane sulfonate,and 6:2 chlorinated polyfluorinated ether sulfonate(alternative of PFOS)being the predominant PFASs.The concentrations of arsenic,cadmium,and lead were detected in the ranges of 4.40–1270.00,0.01–8.67,and 18.00–647.00 mg kg^(-1),respectively,and the concentration of total PAHs was detected in the range of 1.02–131.60 mg kg^(-1).The long-term exposure to mixed contaminants of PFASs,heavy metals,and PAHs led to lower richness and diversity of microbial communities in soil.The soil bacterial communities were mainly composed of Pseudomonas,norank_p_GAL15,Leptothrix,norank_o_Rokubacteriales,and Acinetobacter.Correlations between soil environmental factors and microbial communities indicated that cation exchange capacity and total phosphorus were two key factors in shaping the composition of native microbial communities.Furthermore,Arthrobacter,Leptothrix,and Sphingobium were found to be significantly positively correlated with PFAS concentrations,indicating that these genera could tolerate the stress exerted by PFASs,along with the stress imposed due to the presence of heavy metals or/and PAHs.

Feasibility of Tea Saponin-Enhanced Soil Washing in a Soybean Oil-Water Solvent System to Extract PAHs/Cd/Ni Efficiently from a Coking Plant Site

Mixed contaminated brownfield sites have brought serious risks to human health and environmental safety. With the purpose of removing polycyclic aromatic hydrocarbons （PAHs） and heavy metals from a coking plant site, an innovative technology for ex-situ washing was developed in the present work. The combination of 15.0 mLL-1 soybean oil and 7.5 g L-1 tea saponin proved an effective method to extract co-pollutants from soil. After two consecutive washing cycles, the efficiency rates of removal for 3-, 4-, 5（＋6）-ring, and total PAHs, Cd, and Ni were approximately 98.2%, 96.4%, 92.3%, 96.3%, 94.1%, and 89.4%, respectively. Meanwhile, as evaluated by Tenax extraction method and metal stability indices, the residual PAHs and heavy metals after consecutive washing mainly existed in the form with extremely low bioaccessibility in the soil. Thus, in the soil after two washing cycles, there appeared limited environmental transfer risk of co-pollutants. Moreover, a subsequent precipitation method with alkaline solution and PAH- degrading strain Sphingobium sp. PHE9 inoculation effectively removed 84.6%-100% of Cd, 82.5%-91.7% of Ni, and 92.6%-98.4% of PAHs from the first and second washing solvents. The recovered solvents also exhibited a high recycling effectiveness. Therefore, the combined cleanup strategy proposed in this study proved environmentally friendly, which also played a major role in risk assessment and marlagement in mixed polluted sites.