Study On The Engineering Application Of Ex-situ Bioventing Remediation In Coking Contaminated Site

This experiment focuses on the research on the remediation of coking contaminated soil mainly contained polycyclic aromatic hydrocarbon(PAHs)by the technology of bioventing.Three groups of 50m3 soil were selected,and gradient conditions were set to carry out pilot test to study the removal effect of target pollutants and the most appropriate test ventilation conditions and bacterial dosage.On this basis,500 m3 scale soil was selected to carry out the productive test,the removal effect of the target pollutant was studied,the removal trend of the pollutant was fitted,the changes of the gas composition and the physical and chemical properties parameters of the soil in the process of bioventing were discussed,and the engineering economy was analyzed.The main conclusions of this study are as follows:According to different ventilation volume and bacteria addition volume,3 groups 50 m3 soil experiment B,C and D was set up in the pilot test of ex-situ bioventing.In the 96 day test cycle,the target pollutants benzo[a]pyrene,benzo[a]anthracene,dibenzo[a,h]anthracene,Indeno[1,2,3-cd]pyrene all had good removal effect,and the pollutant concentration was lower than the target value at the end of the test.Between 20th and 40th day,the amount of ventilation and bacteria added had a significant effect on the concentration of pollutants.The pH of different piles had been stable at about 8.5,the soil water content had decreased significantly,and the larger the ventilation volume was,the more obvious the decrease was,the organic matter content had decreased significantly,and the smaller the ventilation volume was,the more obvious the decrease was.According to the results of pilot test,the medium ventilation volume with 10%microbial agent addition had been selected for production test.500m3 scale soil was carried out for the productive experiment in 96 days:the initial concentration of benzo[a]pyrene exceeded 22 times,all of which reached the standard in 68 days,and the final removal rate was 99.1%;the initial concentration of benzo[a]anthracene exceeded 1.06 times,all of which reached the standard in 5 days,and the final removal rate was 98.9%;the initial concentration of benzo[a,h]anthracene exceeded 37.44 times,basically reached the standard in 68 days,and the final removal rate was 97.9%;The initial concentration of Indeno[1,2,3-cd]pyrene exceeded 10.99 times,all of which reached the standard in 68 days,and the final removal rate was 90.9%.Naphthalene,chrysene and benzo[k]fluoranthene were not target pollutants,and the initial concentration was mostly lower than the standard,but the concentration fluctuated in the process of bioventing and also decreased to different degrees.The initial concentration of benzo[b]fluoranthene at some points exceeded the standard,and all reached the standard in 68 days.Fitting the removal process of benzo[a]pyrene,benzo[a]anthracene,dibenzo[a,h]anthracene,Indeno[1,2,3-cd]pyrene,the removal coefficients were 0.0445 d-1,0.0284 d-1,0.0386 d-1 and 0.096 d-1,respectively,and the half lives under the test conditions were predicted to be 16 days,25 days,18 days and 8 days respectively.The average value of oxygen content at each point in the pile fluctuates,but it was close to the measured value in the atmosphere.Most of the points were slightly lower than the measured value,and the oxygen content at different depths of the pile had no regular significant difference;the carbon dioxide content at each point in the pile fluctuates significantly,which was far higher than the measured value in the atmosphere at the same time,and the lower layer of carbon dioxide content at different depths was slightly higher;the pH between different depths had been stable at about 8.5,the soil water content had been declining and the deep layer had declined relatively fast.The content of soil organic matter in different depths had shown a downward trend and the deep layer had declined relatively fast.In this productive test,the engineering cost was 204000 yuan,and the remediation cost was about 408 yuan/m3;the R&D cost was 153400 yuan,and the whole test cost was 715 yuan/m3;compared with the cost of other remediation technologies for disposal of PAHs contaminated soil,the ex-situ bioventing technology in this engineering test had obvious economic advantages.