| BTEX is a kind of highly toxic organic compound,which is easily soluble,volatile and has a strong migration capacity as it is discharged into the environment in the production process of petroleum industry,automobile,decoration and organic solvents.It can quickly penetrate into the soil and groundwater,thus migrating and diffusing,and remain in the groundwater environment for a long time.At the same time,BTEX compounds have serious harm to human health,even at very low concentrations will produce biological toxicity.Biological treatment of benzene series has become the development direction of benzene series treatment with low cost and small secondary pollution.This paper mainly involves the screening of bacteria degrading benzene series,the study of degradation characteristics of dominant strains,the construction of the quantity-effect relationship of the immobilized microbial system and the study of the removal mechanism of benzene series.In this experiment,sludge samples were collected from the oxygen-consuming tank of the sewage treatment plant affiliated to liaoyang petrochemical company.Under the condition of 10 ?,benzene series was used as the only carbon source.After enrichment,separation and screening,a total of 5 strains of benzene series degradation bacteria were screened.According to the physiological,biochemical and 16 S r RNA molecular biological identification,strains DS1 and DS3 belong to Pseudomonas sp.,DS2 and DS4 belong to Bacillus sp.,and DS5 belong to Staphylococcus sp.The gas chromatograph was used to quantitatively analyze the ability of five strains of bacteria to degrade benzene series substances.It was found that DS4 bacteria had the highest degradation efficiency of benzene series substances,with the degradation rate of o-xylene,m-xylene and p-xylene reaching 96.41%,p-ethylbenzene 95.38%,p-toluene80.37% and p-benzene 63.92%.The degradation rate of p-ethylbenzene and xylene was up to 90.51%,and that of p-toluene was up to 79.23%.The degradation rate of p-toluene was the lowest,which was 49.97%.DS2 bacteria had the worst degradation efficiency of benzene.Therefore,DS1 and DS4 bacteria were selected as the dominant degradation bacteria of benzene series as the subsequent research objects.The growth curve,optimump H,salinity and temperature of the two strains were investigated.The two strains were both suitable to grow between p H of 5-7.The addition of salt inhibited the growth of DS1 bacteria,the optimal salinity of DS1 bacteria was 0%,the optimal salinity of DS4 bacteria was 1%,and the optimal temperature was 30?.Polyurethane foam is a kind of microbial immobilized carrier material widely used at home and abroad,which is friendly to microorganism and water environment,relatively low cost,wide source and suitable for large-scale application.In this study,the dominant strain was immobilized with polyvinyl alcohol(PVA)to simulate the shallow groundwater environment in Daqing area.Coupled polyurethane foam was used to analyze the dose-effect relationship of BTEX degradation reaction and obtain the best process parameters.The initial concentration of benzene series was 400mg/L,the p H value was 6.5,the optimal temperature was 10 ?,the Fe ion concentration was 16mg/L,the Mn ion concentration was 12mg/L,the optimal ininoculation amount was 3 pieces,the volume ratio was 40.5%,the degradation rate of benzene series reached 91.86% after 48 h culture of the immobilized system.The removal experiment of benzene series in simulated low-temperature groundwater showed that the removal rate of benzene series at 48 h was98.92% and the final concentration of benzene series was 4.19mg/L among the simulated water samples with the initial concentration of benzene series at 400mg/L.In the early stage,the adsorption of polyurethane foam contributes a lot to the removal of benzene series.When the adsorption reaches saturation,biodegradation is the more important removal mechanism.The microbe in the carrier was observed by scanning electron microscope,and the pores crisscrossed on the polyurethane foam provided the supporting framework for the growth of the micelles.Moreover,a spectrophotometer was used to determine the biomass changes in the carrier with the initial concentration of different benzene series.When the concentration of benzene series was 400 mg/L,the biomass attached to polyurethane foam carrier could reach 6734.41?g/g on average.Under conventional non-stationary conditions,the protein content in the bacteria solution was 71.48?g/m L.The immobilized bacteria could better adapt to the environment polluted by benzene series in groundwater under low temperature.The biological carrier filler provided a foundation for industrial application. |
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