Study Of Biochar Immobilized Bacteria And Its Removal Of PAHs In Soil

Polycyclic aromatic hydrocarbons?PAHs?,which are the ubiquitous pollutants in the environment,pose high risks to human health due to their potential toxicity,carcinogenicity and mutagenicity.Therefore,the remediation of PAHs-contaminated soil has become one of the hot point.The microbial degradation as a fundamental process for PAHs-removal with the advantages of environment-friendly and cost-effective plays an important role in the fate of PAHs in the environment.Immobilized technology is an important technique for bioaugmentation,which played a great potential role for soil remediation.But few researchs for using biochar as the carriers of immobilization were made,further discussion are needed.In this study,a PAHs-degrading strain was isolated from PAHs-contaminated soil,and biochar was chosen as carriers to immobilize strain via adsorption.The performance of immobilization was represented by the abundance of nidA gene and the activity of dehydrogenase.In addition,immobilization conditions were investigated.After that,the removal rate of PAHs was investigated in slurry bioreactor.The main conclusions of this work are drawn as follows:?1?A PAH-degrading bacteria ZL7?Mycobacterium sp.?was isolated from the soil collected from Beijing coking plant.There was 90.32%of pyrene was removed by ZL7in MSM solution at an eight-day incubation period.ZL7 has ability of degrading phenanthrene,benzo?a?pyrene,benzo?a?anthracene,chrysene,benzo?b?fluorene and benzo?k?fluorene.?2?The optimum conditions of immobilization were choosing LB medium,and the ratio of biochar to cell suspensions?W/V?and immobilization time were 1:30 and 24 h,respectively.?3?The removal rate of pyrene in MSM solution by the immobilized materials made by rice straw biochar,pig manure biochar and soybean straw biochar was more than96%.?4?Enhanced biodegradation of PAHs in historically contaminated soil by rice straw biochar and pig manure biochar immobilized ZL7 was observed in slurry bioreactor.The optimum conditions of rice straw biochar immobilized ZL7:the ratio of soil to water was 1:10?W/V?,immobilized materials,the concentration of salicylic acid was 2g·kg^-1and the concentration of Brij30 was 0 g·kg^-1.The removal rate of PAHs was56.70%.The optimum conditions of pig manure biochar immobilized ZL7:the ratio of soil to water was 1:10?W/V?,immobilized materials,the concentration of salicylic acid was 0 g·kg^-1and the concentration of Brij30 was 10 g·kg^-1.The removal rate of PAHs was 43.89%.In conclusion,the optimum conditions of immobilization of 5 biochar are different,and the immobilized materials can enhance the removal of PAHs in PAHs-contaminated soil.The result offer the theory support to the research for enhancing biodegradation by the technique of immobilization.