Ex-situ Soil Vapor Extraction Remediation Trial Of The Coking Contaminated Soil In Jiangsu

This trial selects a coking contaminated site in Jiangsu to study.According to the pollution characteristics of the site and determining the value of the remediation targets in the soil,the ex-situ SVE technology was selected as the remediation technology for the VOC contaminated soil on the basis of the site conditions and the comparison of the remediation technology.The study on the pollution characteristics of the site showed that the concentration of 1,2,4-Trimethylbenzenein in the soil was mainly concentrated in the cold drumelectric trap,the surface soil of the sewage treatment station and the desulphurization section,and the middle and lower layers of coke oven area,and the contaminated soil was selected as the trial soil.Through evaluation,the soil remediation target value of 1,2,4-Trimethylbenzenein was determined to be 7.98 mg/kg.After 153 days of SVE system operation,the concentration of 1,2,4-Trimethylbenzenein at every monitoring point in the soil pile gradually decreased with the operation of SVE,and gradually tended to be uniformly distributed in the soil mound.The concentration range of 1,2,4-Trimethylbenzenein at all sampling sites was decreased from initial 12.59~67.62mg/kg to 0.53~3.59 mg/kg,and the average concentration decreased from 35.08 mg/kg to 1.63 mg/kg,and the average removal rate was 95.33%.Fitting the change of 1,2,4-Trimethylbenzenein concentration at each sampling point,the removal rule of target pollutant was obtained,and the half life of 1,2,4-Trimethyl benzenein removal was about 55 days.The operation of SVE remediation technology will affect the moisture content in the soil.With the operation of the SVE system,the moisture content in the soil decreases gradually,and the average moisture content of each point decreases from 25.62% to 19.35%.Through data correlation analysis,the higher the soil moisture content was,the lower the pollutant concentration was,and the increase of moisture content is not conducive to the removal of target pollutants.When the moisture content is 21%~24%,the removal rate of 1,2,4-Trimethylbenzenein is faster.The content of organic matter in soil is basically stable in 0.92%~4.06%,and the content of organic matter at the initial soil sampling point has little change,which has no significant effect on the removal of target pollutants by SVE operation.Before the SVE remediation enters the "trailing" period,the volume of the pump is positively related to the removal rate of the pollutants,and the greater the volume of the pump,the higher the removal rate of the pollutants.When the exhaust volume was controlled at 3623 ~4125 m3/h,the removal rate of 1,2,4-Trimethylbenzenein was the highest.The temperature has noticeable influence on the airflow uniformity in the pite.The remediation effect is better with the increase of soil temperature.