Experimental Study On Bioremediation Technology And Mechanical Properties Of Petroleum Hydrocarbon Contaminated Soil

Oil is one of the most important energy sources for human beings.Due to natural disasters or improper exploitation,a large amount of crude oil directly or indirectly enters into the soil,resulting in soil petroleum hydrocarbon pollution.In order to solve this problem,gradient dilution method,response surface analysis,ultrasonic extraction ultraviolet spectrophotometry and triaxial test were used to screen the petroleum hydrocarbon degrading bacteria,optimized the culture conditions and degradation conditions,and studied the remediation effect of petroleum hydrocarbon contaminated soil under different remediation methods and the change of mechanical properties of petroleum hydrocarbon contaminated soil before and after remediation.The research and theoretical analysis provide scientific basis for microbial remediation of petroleum hydrocarbon contaminated soil.The main work and achievements of this paper are as follows:(1)Five strains with excellent degradation performance were screened and the best culture conditions were determined.Using LB medium as the substrate,five strains of bacteria with excellent degradation performance for petroleum hydrocarbon contaminated soil were isolated and extracted from petroleum contaminated soil,and the degradation ability of the extracted strains was preliminarily determined with oil reducing medium as the substrate,and the optimal culture conditions were determined.(2)The optimal degradation conditions of five strains were determined by single factor test and multi factor test.Single factor test and multi factor orthogonal test were used to determine the residual oil content of the repaired petroleum hydrocarbon contaminated soil.The results showed that the degradation effect of petroleum hydrocarbon degrading bacteria was relatively significant when the p H value was 6-8,the temperature30-35?,the soil moisture content 15%-25% and the inoculation amount of degrading bacteria 1-2.5ml.Under the multi factor orthogonal test,the best degradation effect of mixed bacteria was obtained.The optimum conditions were as follows: p H 7,temperature32?,soil moisture 25% and inoculum 1ml.(3)The results showed that phytoremediation,microbial remediation and phyto microbial remediation were effective in the remediation of diesel contaminated soil.Diesel oil prolonged the germination time of plant seeds,and had more significant effect on tall fescue seeds.A small amount of diesel oil could improve the germination rate of plant seeds.The plant biomass(fresh weight)and plant height of tall fescue were higher than that of alfalfa.There was no significant difference in the effects of phytoremediation and phyto microbial joint remediation on plant biomass and plant height at the early stage of the experiment,the effect of combined phytoremediation was better than that of phytoremediation at the later stage of the experiment.The results showed that the effect of remediation was better than that of phytoremediation;under the same remediation conditions,the best remediation methods were different at different remediation stages,and the lower the diesel concentration was,the better the remediation effect would be.(4)The mechanical properties of diesel contaminated soil and microbial remediation of diesel contaminated soil were revealed.With the increased of oil content in soil samples,the liquid limit of diesel contaminated soil first increased and then decreased,and reached the peak when the oil content of soil samples was 8%;diesel contaminated soil belonged to medium compressibility soil,and the oil content of soil samples had a great influence on the compression coefficient,compression index and compression modulus of diesel contaminated soil;the cohesion of diesel contaminated soil was greatly affected by the diesel concentration,and the internal friction angle increased with the diesel concentration.Compared with the same concentration of diesel oil contaminated soil,the cohesion of high concentration diesel oil contaminated soil increased,while the internal friction angle decreased,and the difference became larger with the progress of remediation.