Isolation?Degradation Characteristics Of PAHs-degrading Bacteria And Its Application In Combination With Chemical Oxidation

In recent years,with the implementation of a series of urban development strategies in China,a large number of industrial enterprises have shut down or relocated,thus exposing a large number of industrial pollution sites which accumulated for many years.As one of the typical pollutants in industrial sites,polycyclic aromatic hydrocarbons pose a serious threat to the ecological environment and human health,research on the repair technology of polycyclic aromatic hydrocarbon contaminated sites has also received widespread attention.This study takes a steel industry site in Shandong,China,as the research object.Firstly,we explored the relationship between microbial community structure and pollutant concentration in the soil of the site.And than,one of the degradation bacteria was isolated,and it's degradation performance and degradation mechanism of polycyclic aromatic phenanthrene,a typical pollutant in the site,were studied.At last,the highly effective degradation bacteria and the chemical oxidant persulfate were acted together on the contaminated soil,for studying the degradation of phenanthrene in soil by chemical pre-oxidation combined bioaugmentation and biostimulation.The main results of this study are as follows:?1?The soil contaminated in this steel industry site,is dominated by polycyclic aromatic hydrocarbons?PAHs?,and heavy metals are less polluted.The microbial diversity in the coking area was significantly lower than that in the non-coking area?all p<0.05?,and the microbial community structure was also significantly different?p=0.001?.Environmental factor correlation analysis results show that contaminants such as arsenic,polycyclic aromatic hydrocarbons and chromium,and soil properties such as soil moisture content,total nitrogen content and total phosphorus content are the main factors leading to differences in microbial community structure in the industrial site.?2?Acidovorax sp.JG5,a degradation bacterium capable of highly degrading phenanthrene,was screened and isolated from the contaminated soil which use phenanthrene as the sole carbon source and energy source.The optimal growth conditions of Acidovorax sp.JG5,30?,pH 7.0,and the NaCl salinity is 0⁰.5%.Acidovorax sp.JG5 can fully biodegradable concentration to 100²00 mg·L^-1 of the phenanthrene,for a high concentration of 500¹500 mg·L^-1 phenanthrene degradation efficiency can reach more than 95%.The metabolic pathway of Acidovorax sp.JG5against phenanthrene is mainly through the simultaneous oxidation of phenanthrene at C3-C4 and C9-C10 sites.Phenanthrene was metabolized into phthalic acid and salicylic acid by the two pathways of phenanthrene?3,4-phenanthrene glycol?2-hydroxy-1-naphthalic acid and phenanthrene?9,10-phenanthrene glycol?9,10-phenanthrene quinone?2,2'-biphenylic acid,and finally entering the TCA cycle to complete the metabolism.?3?Low-concentration persulfate pre-oxidation combined bioaugmentation and biostimulation using high-efficiency degrading bacteria and different types of nutrients were used in the phenanthrene contaminated soil,for studied the degradation effects of phenanthrene in soil by chemical pre-oxidation combined bioaugmentation and biostimulation.The results shows that chemical oxidation combined with microbial remediation can effectively improve the degradation of phenanthrene in soil.The final degradation efficiency of phenanthrene increased by 8.08%¹8.59%,when the phenanthrene degradation bacteria and nutrients were added after chemical pre-oxidation.The simultaneous addition of degradation bacteria and nutrient N was the most effective way to promote the degradation of phenanthrene in soil.