Effect Of Surfactant For Bioremediation Of Polycyclic Aromatic Hydrocarbons Contaminated Soil By Immobilized Microorganisms

In view of the pollution of polycyclic aromatic hydrocarbon soils,the surfactants to enhance the immobilization of microorganisms are used for soil remediation.The surfactants has good and quick effect on desorption of PAHs in soil and is an effective method to enhance the microorganisms m remediation.In this paper,Tween 80 and sodium dodecyl benzene sulphonate?SDBS?has obtained results of the optimal compounding ratio and amount enhanced immobilized microorganisms for PAHs contamination soil remediation.The enhancing effect of surfactants on PAHs remediation was studied by periodically measuring the mass content of PAHs in the soil.The soil urease,catalase activity,pH,electrical conductivity and organic mass content were periodically measured,and the mechanism of surfactant influence on microbial activity in soil was examined by correlation analysis.To examine the influence of straw carrier decomposing on the degradation of PAHs by immobilized microorganisms and the influence of surfactants on microbial community structure and straw carrier decomposing by periodically measuring humic acid mass content in soil analysised for correlation of humic acid mass content and phenanthrene mass content in soil and bacterial community structure before and after remediation.Among the six selected strains J-1,J-2,J-3,J-4,J-5,and J-6,the highest degradation rate of phenanthrene for 5 days were J-1,J-4,and J-6,for 43.30%,35.71%and 37.47%,respectively.J-1,J-4 and J-6 respectively belong to genus Alcaligenes sp.,Arthrobacter sp.and Bacillus sp.identified by physiological and biochemical experiments and molecular biology methods.Simulated experiments of multi-carbon sources degradation with toluene as the aromatic component,n-heptane as the saturated component,and phenanthrene as the colloidal asphaltene showed that J-1,4,6 had degradable ability of toluene,n-heptane and phenanthrene,three kinds of carbon sources and the degradation rate of phenanthrene was highest in 72 hours,which were 90.02%,53.23%and 82.58%respectively.Response surface optimization method was used through the flask test and concluded that when sodium dodecyl benzene sulfonate concentration were 0.014 mol?L^-1,and Tween 80 mass concentration were0.45 g?L^-1,the highest degradation of phenanthrene by immobilized microorganism was reched for 55.05%in 5 days.The mass ratio of dodecyl benzene sulfonic acid and Tween 80is 9.76:1.It can be used to guide the mixing of surfactants for enhancing remediation effection by immobilized microorganisms for PAHs contaminated soil.After the surfactants were added to the soil,the degradation ability of the immobilized microorganisms on the polycyclic aromatic hydrocarbons in the soil was enhanced.The degradation rate of phenanthrene in the SMM group was 28.99%higher than that of MM group after 39 days remediation.The correlations between phenanthrene content and urease activity,catalase activity and pH were relatively balanced,indicating that the addition of surfactants improved the living environment of microorganisms in the soil,weakened the restriction of phenanthrene degradation in soil by a certain factor,increased the PAHs availability to immobilized microorganisms and made it possible to repair PAHs contaminated soil better.There is a correlation between the phenanthrene content and the humic acid content in soil,indicating that the increase of humic acid content promotes the reduction of phenanthrene content.Surfactants can help the immobilized microorganisms to form the dominant bacteria for phenanthrene degradation in the soil rapidly,which is very conducive to the remediation of contaminated soil.