Mechanism Of Surfactant-Bacterial Community Enhanced Slurry Reactor For Soil Remediation Of Phenanthrene

Polycyclic aromatic hydrocarbons(PAHs)are persistent organic pollutants and are widely found in the environment.PAHs are widely concerned for their carcinogenicity,teratogenicity,and genetic toxicity.Due to its high hydrophobicity and high fat-soluble solubility,PAHs are prone to accumulate in soil and sediment and enriched in organisms through the food chain,then seriously threatening human health and the ecological environment.Microbial degradation is the main way to remove PAHs in the environment due to its advantages of being environment-friendly and low cost.As a new contaminated soil remediation technology,bioslurry remediation technology can significantly increase the degradation efficiency of PAHs by regulating various environmental factors of microbial degradation.However,there are few studies on the mechanism of action in biological slurry systems.In this paper,the highly efficient degrading bacteria of PAHs were screened from the environment and applied to the repair of biological mud reactors.The distribution of pollutants,surfactants and microflora in the mud reactor and the changes of microbial communities were studied.The mechanism of action of the biofortified mud reactor in the presence of the active agent.In this experiment,the aerobic sludge of the municipal sewage treatment plant is used as the original source of bacteria,and the Philippine is the sole carbon source and energy source.After domestication and enrichment,the microflora MZJ-21 with high efficiency degradation of phenanthrene is screened.Through high-throughput sequencing,it was found that the flora of the flora was reduced from 24 gates to 17 gates.The domesticated flora MZJ-21 was mainly composed of Proteobacteria(84.63%)and Bacteroidetes(10.98%),Chloroflexi(1.97%),and Acidobacteria(1.29%).Species diversity was significantly reduced,and the proportion of bacteria with degradation function increased significantly.Applying the flora to the repair research of phenanthrene-contaminated soil,the optimum conditions for determining the degradation of phenanthrene in the mud system by MZJ-21 are: temperature 30 °C,pH 6,aeration rate at 1 L/min,stirring speed 120 rpm and The ratio of water to soil is 2:1.Addition of 100 mg/L of Tween80 under these conditions revealed that the degradation rate of phenanthrene was 100%at 24 h.Comparing the community diversity before and after treatment with contaminated soil,it was found that the community diversity decreased after treatment,and the proportion of bacteria with degradation function increased.Through electron microscopy and CFU test,it was found that in the mud system with water to soil ratio of 2:1,the flora MZJ-21 and indigenous bacteria were distributed on the soil surface,and the surfactant could promote the adsorption of the soil.At the same time,the generation of EPS also plays a role in the adsorption of polycyclic aromatic hydrocarbons in the biological mud system.The experiment further studied the adsorption and resolution of phenanthrene in a solid phase in a 50 ml centrifuge tube.The aging natural soil with a concentration of100mg/L was added to the microbial or inorganic salt medium to detect the distribution ratio of phenanthrene and surfactant in the mud.Only when the concentration of Tween 80 reached a large concentration(2000mg/L),It was discovered that phenanthrene was resolved from the solid phase to the liquid phase.In the analytical test,the distribution of phenanthrene and Tween80 in the solid-liquid phase is mainly affected by the water-soil ratio.The smaller the water-soil ratio(2:1),the smaller the ratio of phenanthrene to the aqueous phase;when the water and soil are relatively large(10: 1 and 20:1),the analysis of the solid phase in phenanthrene and Tween80 is mainly affected by biosorption,and the addition of microflora reduces the resolution of phenanthrene in the aqueous phase.In order to confirm this result,the adsorption effect of soil on phenanthrene and Tween80 was further studied.The uncontaminated soil was added to the 100mg/L phenanthrene contamination liquid phase.It was found that the distribution ratio of phenanthrene and Tween80 in the water phase and soil phase was mainly affected by the water-soil ratio.When the water and soil were relatively small,the adsorption capacity of the soil phase was large.Most of the phenanthrene and Tween80 are adsorbed in the soil phase;when the soil and water are relatively large,the addition of the flora enhances the biosorption.Through the above experiments,it is proved that in the common mud-soil system with water-soil ratio of 2:1,when the concentration of surfactant Tween80 is 100mg/L,most of the phenanthrene,Tween80 and the flora are distributed on the surface of soil particles,biosorption and degradation.The reaction also occurs on the surface of the soil particles.