Study On Screening Of Crude Oil Degrading Bacteria And Lab-Scale Simulation Remediation Of Contaminated Soils

Petroleum is a powerful driving force for the rapid development of modern society. The oil spill will cause soil pollution, agriculture and food production, some teratogenic carcinogenic compounds in the oil enters the body and harm human health. Oil pollution has become a major issue of economic development and social progress. Microbial remediation method has low costs, the advantages of simple operation and no secondary pollution, is one of the most promising methods in soil remediation.This research focuses on petroleum-degrading bacteria (10-1,10-2,10-3, and 10-4) as the object of study, building the high efficient oil degradation bacterium 10#, in the form of free and immobilized bacteria, respectively. Be added to the simulation of petroleum-contaminated soil in the comparison of two bacteria types on the remediation of petroleum-contaminated soil to get the following results:Study on the growth curve experiment showed that strains, in beef extract peptone medium, can tolerate 5% environmental salinity, the best initial pH of 7, can be prepared seed liguor under the condiation of 30℃,180 r/min,14 h. In the inorganic salts medium with oil as sole carbon source, the strains (10-1,10-2, and 10-3) has a consistent growth trend, showed synchrony.Simulation of microbial remediation of petroleum contaminated soil tests shows that the degradation bacteria of the best inoculum of 10%, the best ratio of C、N、P in soil is 100:10:1, oil degradation rates are respectively 32.5% for immobilized bacteria,24.9% for free bacteria, and control group is only 8.8%.Related indicators in soil remediation process test results shows that soil pH decreases, decline of solid soil’s pH is greater than the group of free bacteria group, and either of them is greater than the control group. Soil dehydrogenase activity is on the rise, solid group can be up to the highest peak of 17.27μg TF/g (dry weight)/d on the 45th day, while free group can be reached to 14.83 μg TF/g (dry weight)/d on the 30th day, the control group also has a certain degree of enhancement in soil dehydrogenase activity, it’s highest date is 10.67 μg TF/g (dry weight)/d on the 60th day. The contaminated soil respiration can be enhanced by putting free and immobilized banteria agents, it can be reached highest 1.79 mg CO2/g (dry weight)/h at 50th day,2.26 mg CO2/g (dry weight)/h at 60th day, respectively. The soil respiration of control group and natural soil group is 1.06 mg CO2/g (dry weight)/h and 1.42 mg CO2/g (dry weight)/h respectively, which are lower than dosing agent groups above. The components of crude oil before and after degradation were analyzed by GC-MS analysis. The results showed that the strain UV13 could almost completely degrade 19 n-alkanes of C14-C32. This indicated that the strain had a relatively wide spectrum of degradation and has a better effect on the degradation of oil pollutants.Test established on the 10# degrading bacteria repair of petroleum contaminated soil model parameters:Oil concentration in soil 6645.7 mg/kg, the soil moisture content of 15%-20%, about 7.25 initial soil pH, soil nutrient proportion C:N:P= 100:10:1, petroleum-degrading bacteria inoculation 10%. Outdoor experiments bioremediation of petroleum contaminated soil showed that after 40 days of repair, adding solid petroleum degradation bacteria test group was 26.3%, bacteria free add oil degradation test group was 19.2%, in the control group which did not add any agents of soil, the oil degradation rate was 5.9%. Thus, the 10# oil degrading bacteria, can accelerate the degradation of petroleum pollutants in the petroleum contaminated soil bioremediation process, has a certain ability to repair.