| The composition of petroleum is complex,and the self-purification capacity of soil cannot degrade petroleum pollutants in a short time.Although the petroleum pollutants can be effectively removed by physical and chemical means,there are many disadvantages such as high risk of secondary pollution,harsh requirements on conditions,and high repair cost.Microbial remediation has become one of the most promising methods for the remediation of petroleum contaminated soil due to its advantages of low cost,environmental protection and no damage to soil structure.Native oil-degrading bacteria are often more applicable than foreign bacteria.The oil-degrading bacteria screened from contaminated soil belong to indigenous microorganisms,which will not affect the composition and structure of soil microorganisms.Moreover,the competition of native strains is far less than that of non-native bacteria,so it is the first choice for microbial remediation in contaminated soil.Therefore,this thesis screens petroleum-degrading bacteria in a soil-contaminated soil in Shenyang,and discusses the degradation effect of the screened strains on oil.The research content includes the following four aspects:(1)Four local petroleum-degrading microorganisms that can use oil as the only carbon source for their own growth and metabolism were screened and isolated in a soil-contaminated soil in Shenyang,and named SY1,SY2,SY3 and SY4.The four strains were inoculated into blue gel medium,and after removal,it was observed that all four strains could produce blue circles,and the blue circles of SY1 and SY3 were larger and more obvious.The oil drain ring diameter of SY1 and 5.80 mm was obtained by SY1 and 5.80 mm in SY2 and SY4.The four strains screened out were identified by sequencing and sequencing,and SY1 was Bacillus tropicus,SY2 was Microbacterium paraoxydans,SY3 was Acinetobacter johnsonii,and SY4 was Pseudomonas brenneri.(2)The operating parameters of the degradation experiment will also affect the degradation effect of petroleum components to a certain extent.The degradation days(d),initial oil concentration(mg/L)and bacterial dosing amount(%)were changed by univariate experiments to obtain the optimal conditions for the degradation effect of single bacteria on petroleum.The experimental results showed that the optimal degradation days of the four strains were 4 days,and the degradation rates were 28.64%,24.68%,37.98% and 22.32%,respectively,and the oil degradation rate almost no longer increased after the degradation days exceeded 4 days.The optimal initial petroleum concentrations of SY1 and SY3 were 1000 mg/L,with degradation rates of 28.74% and37.63%,respectively,and the optimal initial petroleum concentrations of SY2 and SY4 were 1500 mg/L with degradation rate of 22.62% and 19.04%.The optimal bacterial dosing amount of SY1,SY2 and SY3 was 5%,and the degradation rate reached 30.69%,26.31% and 38.98%.SY4 has a high oil tolerance.(3)The optimal compound ratio of SY1,SY2 and SY3 was 1:1:3,the total addition volume fraction was 3%,and the degradation rate reached 46.68%.The optimal compound ratio of SY1 and SY3 was 2:1,the total addition volume fraction was 5%,and the degradation rate reached 48.22%.(4)The degradation kinetic model of SY1 and SY3 complex bacteria degrading petroleum was constructed,and the regression equation was: y=-0.0878x+7.0634,R2 was 0.9776,and Pearson’s correlation coefficient r was 0.9919,which basically conformed to the first-level degradation kinetic model. |
