Study On The Application Of Fungi And Bacteria In Remediation Of Petroleum Contaminated Soil

The pollution of petroleum hydrocarbons is a common concern in the world.At home and abroad,many scientists have carried out extensive and intensive research on the treatment of petroleum hydrocarbon pollutants.For the remediation of petroleum contaminated soil,the commonly used methods are heat treatment remediation,electrokinetic remediation,chemical oxidation,solvent extraction,curing / stabilization technology,and bioremediation is the most effective way to control the pollution of petroleum hydrocarbons,one of the technologies that has the advantages of high efficiency,economy,no secondary pollution and wide application range.However,the complexity of petroleum properties and composition determines the complexity of the biodegradation process.The petroleum content can be metabolized by the single strain limitedly.How to combine degraded strains to degrade petroleum hydrocarbons effectively is one of the problems to be solved in this experiment.It is highly efficient and feasible to realize the remediation of petroleum hydrocarbon pollution with biological method.In this study,we propose a screening of a strain of biodegradable bacteria which can produce surfactant and a strain of fungi that can degrade petroleum hydrocarbons efficiently to form a microbial compound preparation.And when they are put into the aqueous media,the effects of temperature,pH,inorganic ions and trace elements in aqueous media on the degradation characteristics of petroleum hydrocarbons are studied.And then,through single factor and orthogonal optimization,the effects of bacteria inoculation amount,soil water content and organic conditioning agent on the capacity of degradating petroleum by high efficiency petroleum degrading bacteria are studied.Finally,through the experiment conducted in the simulated contaminated soil,and according to the accuracy and feasibility of engineering parameters detected dynamically,the best engineering parameters are determined when bioprocessing method is used to dispose contaminated soil of high concentration petroleum,providing data reference for the field application study and large-scale application of bioprocessing method.The main conclusions are as follows:A strain of biodegradable bacteria,which can produce surfactants and a strain of fungi,which can degrade petroleum hydrocarbons efficiently,can be extracted from petroleum contaminated soil,after repeated enrichment-separation and purified cultivation,in the inorganic salt medium,where the petroleum is regarded as the sole carbon source.After the test of morphology and molecular biology,biodegradable bacteria and fungi are respectively identified as Rhodococcus erthropolis and Candida tropicalis;The results of the study on a single bacterium and the mixed bacteria in the aqueous medium show that temperature has a great effect on the degradation of petroleum hydrocarbons by microorganisms.The optimum degradation temperature is from 25 to 30?.The degradation rate of mixed bacteria reaches 58.4%;pH value has a great effect on the degradation of petroleum hydrocarbons in microorganisms.Each strain is suitable for the degradation of petroleum hydrocarbons in the environment of pH = 7-9.The effect of inorganic ions on the degradation of petroleum hydrocarbons is obvious.Compared with the control group,the degradation rate of the experimental group has increased by 19.3%-59.3%;The results of orthogonal experiment show that the optimum engineering parameters are 15% of the dosage of bacteria,60% of the soil water content and 5% of the organic conditioner,the influencing degree of them are: the dosage of bacteria >the organic conditioner >the soil water content.The results show that the optimum engineering parameters obtained by orthogonal optimization experiment are accurate.By setting the best parameters,the experiment lasted 63 days in the simulation field.After that,the degradation rate of petroleum hydrocarbons in the reactor reached to 64.82%,which was consistent with the orthogonal experimental results.The polymerase chain reaction-temperature gradient gel electrophoresis technique(PCR-TGGE)results showed that the microbial community structure of the system was simpler than before bioaugmentation.However,with the addition of the fortified bacteria,organic conditioning agents and nutrient solution,the succession of the microbial population structure of the system was obvious.The Shannon-wiener index rose from 2.284 to 2.786.The population structure enriched and the diversity increased.By detecting,the results showed that the two dominant functional degradation bacteria R.erthropolis and C.tropicalis could stabilize in the polluted soil and accelerate the degradation of petroleum hydrocarbons,improve the degradation efficiency and shorten the repair time,to achieve efficient oil remediation of soil pollution.