Study On The Efficiency Ofhigh-Effective Bacteria To Enhance The Degradation Of Ethylbenzene In Groundwater By Aeration

In recent years,due to the rapid development of China’s economy,the demand for petroleum resources has greatly increased.Various parts of the country are actively exploring and developing oil fields,and many new oil fields have been discovered and exploited.However,accidents often occur in a series of processes such as exploration,drilling,oil extraction,storage,transportation,and processing,resulting in a large amount of petroleum substances entering the soil and groundwater environment,posing a continuous threat to human life safety.In this paper,aiming at the highly toxic and volatile petroleum pollutant ethylbenzene,the highly efficient petroleum degrading bacteria selected from typical oil field contaminated sites were selected,and quartz sand was used to simulate the aquifer medium in the contaminated sites.Field simulation experiments were carried out through one-dimensional cylinder and two-dimensional box experimental devices to study the effects of aeration flow,aeration temperature and other factors on the efficiency of air aeration and biological aeration to degrade ethylbenzene.The main research results obtained in the paper are as follows:1.In order to explore the characteristics of D2 bacteria degrading ethylbenzene,microbial environmental factor optimization experiments were conducted,and 12 single factor parallel experimental groups were set up.The optimal degradation conditions for D2 bacteria were finally obtained as follows: pH=8,40 ℃,130 r/min,additional nitrogen and phosphorus elements added,and C: N: P=100:5:1;2.Isothermal adsorption equilibrium experiment and adsorption isotherm were carried out to determine the physical parameters of the aquifer required for the simulation experiment.The results showed that the adsorption equilibrium time of ethylbenzene on the three quartz sand media was 12h;The distribution coefficients of ethylbenzene in fine sand,medium sand and coarse sand are 2.691 mL/g,1.249 mL/g and 0.827 mL/g respectively.The smaller the particle size of quartz sand medium is,the stronger the adsorption capacity of ethylbenzene is;3.The optimal aeration conditions of air aeration and biological aeration were explored,and the one-dimensional simulation experiment of ethylbenzene removal by aeration was carried out using a self-made one-dimensional cylinder simulation device.The results showed that the degradation efficiency of ethylbenzene in the same quartz sand aquifer depth increased with the increase of aeration flow,and the aeration flow of 400 mL/min was the optimal condition.The removal rate of biological aeration is significantly higher than the final removal rate of air aeration,with the highest removal rate of ethylbenzene reaching 97.07%;Under the aeration temperature conditions of 20 ℃,30 ℃,and 40 ℃,the final removal rate of ethylbenzene reached over 95%.At 50 ℃,adding microorganisms is difficult to survive.4.A self-made two-dimensional sandbox was used to conduct groundwater dynamic simulation experiments to explore the mechanism of biological aeration in the removal of ethylbenzene and the mass transfer effect of ethylbenzene.The results show that under the three aeration temperature conditions,the temperature field in the main water tank is basically U-shaped,and the higher the temperature,the larger the coverage area of the high-temperature area.The higher the temperature,the smaller the concentration of dissolved oxygen in water,and aeration can effectively increase the concentration of dissolved oxygen in water;The dissolved oxygen concentration after adding bacteria is smaller than that without adding bacteria,causing the inverted U-shaped dissolved oxygen concentration field to become a positive U-shaped one.At high temperatures,the volatilization effect of air aeration is very obvious when the concentration of pollutants is high.The U-shaped area formed by aeration can block the upstream diffusion of pollutants and undergo certain degradation;Temperature also has a significant impact on biological aeration.After 24 hours of aeration,the final removal rate of air aeration at 30 ℃ reached 63.90%,and that of biological aeration reached 78.38%;Under the condition of 40 ℃,the final removal rate of air aeration reached 72.57%,and that of biological aeration reached 82.09%;Under thermal enhanced conditions,the remediation effect of biological aeration is better than that of air aeration.