Study On The Optimization Removal Of Benzene Series In Soil Based On SVE

The pollution of soil and groundwater caused by petroleum pollutants is not optimistic.Soil vapor extraction(SVE),as a remediation technology which can remove volatile/semi volatile organic compounds efficiently,is widely used,but also limited by many factors.Especially in areas with frequent fluctuation of groundwater level,the change of soil permeability caused by fluctuation of groundwater level will directly affect the effect of SVE,and the phenomenon of layered soil pollution also exists in the actual polluted sites.At present,in the numerical simulation and field application of SVE technology for oil contaminated soil remediation,the fluctuation of groundwater level and the stratification of pollution are not considered.In this study,benzene series were selected as the characteristic pollutants,and the experimental device of SVE removal of benzene from soil and layered extraction were constructed under the condition of groundwater level fluctuation.Meanwhile,the transport and distribution of Benzene Series in the soil "non-fluctuation zone-fluctuation zone-saturated zone" in the process of groundwater level fluctuation circulation were studied,and the key parameters affecting SVE remediation effect,such as extraction flow,extraction time,extraction method,initial soil moisture content and initial pollutant content,were selected to carry out the study on the difference of benzene removal by SVE under the condition of groundwater level fluctuation and non-fluctuation.The SVE stratified extraction experiment was carried out to study according to the layered pollution of soil,and the removal effect of layered extraction and unlayered extraction on benzene in soil was compared and analyzed.The numerical simulation and optimal design of remediation scheme were carried out in combination with the actual pollution site.The results show that the fluctuation of groundwater level has a significant impact on the distribution of Benzene Series in soil,and the removal effect of SVE on benzene in soil will be significantly improved under the condition of groundwater level fluctuation.At the same time,SVE layered extraction is more suitable for efficiently and energy-saving remediation of layered polluted soil.And the SVE optimization design method we obtained is applied to the actual design process of SVE remediation scheme for oil contaminated site,and the actual optimal removal effect is explored with the help of Tough2.The main conclusions are as follows:(1)The fluctuation cycle process of groundwater level has a great influence on the distribution of Benzene Series in the "non-fluctuation zone-fluctuation zone-saturation zone" of soil:in the process of groundwater level rising,the benzene series which have been in the natural state and gradually decreased from top to bottom will gradually rise and float on the water level surface with the groundwater level;in the process of groundwater level falling,the benzene series which are concentrated on the water level surface will decline with the groundwater level During the whole dry wet cycle,most of the benzene series are located in the non-fluctuation and fluctuating zones,while less of the benzene series was distributed in the saturated zone.(2)In the range of extraction time,extraction flow,extraction method,initial soil moisture content and initial pollutant content,we chosen.it is found that the removal rate of benzene by SVE under the condition of groundwater level fluctuation is can be increased by 10%than that under the condition of non-fluctuation.As an important influence parameter,extraction flow can directly change the removal rate of benzene by SVE under the condition of groundwater level fluctuation.Under the condition of groundwater level fluctuation,the removal effect of SVE on benzene in different soils of "non-fluctuation zone-fluctuation zone-saturation zone" is also significantly different,which mainly shows that the removal effect of SVE on fluctuation zone and non-fluctuation zone is better than that on saturation zone.(3)Under the same conditions of extraction flow,extraction time and extraction method,for the same soil initial moisture content and pollutant initial content,the removal rate of layered extraction can be increased due to the smaller flow loss during extraction.Among them,water content has a greater impact on layered extraction,and the enhancement degree of layered extraction on benzene removal efficiency in soil decreases with the increase of water content than that of unlayered extraction;while the remediation effect of layered extraction on soil with higher pollutant content is more significant than that of unlayered extraction.(4)According to the SVE optimization design method we obtained from the experiment,the actual design process of SVE remediation scheme for oil contaminated site was designed and optimized.The optimization results show that SVE layered extraction can be used to repair the layered pollution in the actual contaminated site,and the well screen of SVE punping well can be optimized,which can save the repair cost.In view of the fluctuation of groundwater level in the actual site,the repair efficiency of SVE can be increased by more than 10%compared with that under the condition of non-fluctuation of groundwater level.