| With the development of oil industry, the problem of oil-contaminated soil becomes more and more serious. To solve the problem, oil bioremediation is hot topic for its great significances and wide application prospects. However, lacking of stability and adaptability strains is one of important problems in bioremediation. In this paper, oil-degrading strains were obtained through screening from heavy oil and oil-contaminated soil of Chang qing gas field. The identifications and properties of strains were also studied. The mixed flora of bacteria-fungal was constructed by combination of oil-degrading strains and experiment of L9 (34) orthogonal. Changes of composition of oil before and after bio-degradation by mixed flora went on by GC-MS. Finally, oil-contaminated soil bioremediation was researched in order to verify the effect of mixed flora.The experiments were carried on to provide theoretical basis for the practical application and further evidence for the research of biological agents.34 strains of bacteria,5 strains of moulds,2 strains of yeast were purified from the sample.After further screening,bacteria as M-1, M-10, M-17, M-21, M-23, M-28 and fungal J-1, J-2, Y-1 were better than the other, all of that can grow in the oil agar plates. The strains were identified as Pseudomonas sp. M-1, M-10, M-23, Alealigenes sp. M-17, Microbacterium sp. M-21, Bacillus sp. M-28, Cunninghamella sp. J-1, Fusarium sp. J-2, Saccharomyces sp. Y-1. Bacteria M-23, yeast Y-1 had high tolerance for oil. M-23's degradation rate and viscosity reduction rate reached 57.31% and 32.25% respectively, of which can produce bio-surfactant making crude oil 1.75cm spreading and 3μm～6μm oil droplets. The viscosity reducing of bacteria M-17 was inferior to bacteria M-23. Bacteria M-21 also can produce surfactant.The study showed that mixed flora H14 with bacteria M-23, M-21, M-17, yeast Y-1 was significantly in oil-degradation.The optimum inoculation ratio of P1 consisting of strains as mixed flora H14 was that bacteria M-23, M-21, M-17, yeast Y-1 respectively accounted for 1.5%,1.5%,1%,1.5%.The oil degradation rate was 70.98%. PI and mould J-1 constructed bacteria-fungi degradation systemT2, of which degradation rate was 75.35%.GC-MS showed that oil components changes before and after degradation, mainly using the C27. The Pr/Ph, Pr/nC17 and Ph/nC18 ratio increased 0.641,0.922,0.395 respectively.The restoration experiment of oil-contaminated soil with 13.28 mg/g oil by mixed flora T2 showed that soil degradation rate of experiment groups and the control group reached 72.22%,79.71%,5.79% after 110days. The degradation rate of experimental group2 with sawdust was 7.59% higher than the group1 without sawdust. The account of bacteria played an important role in the process of repair. The oil component in the soil changes after restoration. The degradation rate of saturated hydrocarbons was 85%, followed by aromatic hydrocarbons 65%, the degradation rate of asphaltenes was less than 52%. The saturated hydrocarbon and aromatic hydrocarbon degradation rates of experimental group2 can reach to 90% and 69%. In short, the study provides theoretical basis for the petroleum-contaminated soil restoration. |
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