Field Study On The Soil Venting And Microbial Combinded Remediation Of Petroleum Hydrocarbons-Contaminated Soils

Microbial remediation technology of contaminated soil has the advantages oflow expense, high efficiency, and no secondary condamination, et al. So thistechnology could be used to treat the soil which is been contaminated by theprtroleum hydrocarbons, and the heavy metals, et al. But this technology also has thedisadvantages of long remediation circles and the requirement of specific excellentdegrading bacteria which is difficult to get. Soil Venting (SV) is gaining acceptance asa remediation technology for unsaturated soils contaminated with volatile organiccompounds (VOCs). This technology includes the technology of Soil VaporExtraction (SVE), and the technology of Bioventing (BV) which is derived from theSVE technology, etc. But the application of the SVE technology requires the highpermeability of the contaminated soil that is treated, and also this technology has taileffect. In the engineering project, the single remediation technology for thecontaminated soil is actually not enough to solve the problem of soil contaminationwith petroleum hydrocarbons completely. So the in-depth research on the couplingtechnology of SVE/BV technology and microbial remediation technology is verynecessary.In this work, the microorganisms existing in the heavily contaminated soil fromLiaohe Oil Field and the lightly contaminated soil from some field of TEDA (TianjinEconomy and Development Area) was isolated and screened out. Four types of highperformance microbial bacteria which could be used to degrade the crude oil and lightoil was obtained. The suitable growth conditions for these dominant microbialbacteria were determined. Research on the selection of immobilized carriers for thesemicrobial bacteria was also conducted. In this research, the properties of bacteriaadsorption quantity, moisture performance, density of the immobilized carriers wereconsidered. So the best carrier for the soild bacteria under the experimental conditionswas determined.Using the typical silty clay from the TEDA field, the crude oil adsorptionperformance of this type of soil and the performance of crude oil biodegradation withthe dominant microbial bacteria was discussed via the crude oil adsorptionexperiments and the crude oil biodegradation experiments. The mechanism of theadsorption of crude oil in the soil and the parameters such as adsorption constants was determined with the crude oil adsorption equilibrium experiment. Using the biologicalmud method, the performance of the bidegradation of crude oil in the silty clay wasdetermined, and the first-order’s bidegradation kinetic model was corrected. Theboosting effect of surfactant on the biodegradation of crude oil in the soil was alsoobserved in this work. And it was found that the rhamnolipid could greatly acceleratethe rate of degradation of crude oil in the soil especially at the beginning ofbiodegradation. In the field application research of high performance petroleumhydrocarbons degradation soild bacteria, the good effect of microbial solid bacteria inthe treatment of oil soil from the Liaohe Oil Field was validated using the biodegradationoff-situ remediation approach of natural ventilation (with the timely excavation for thesoil) technology, so these microbial bacteria appears obvious advantages over thenatural degradation when used to treat the crude oil in the soil.The in-situ remediation experimental equipment system was set up in a TEDAfield which was lightly contaminated by light oil. Using this experimental equipmentsystem, the coupling treatment mechanism of in-situ microbial remediation andSVE/BV for the volatile petroleum hydrocarbons was systemically observed. Theimportant parameters such as the vapor pressure distribution, air permeability ofunsaturated area soil (silty clay), and the pressure influnce radius was determined viathe single steady state extracting experiments and the air respiration test.During the phase of in-situ natural domestication of the field dominant nativemicrobial bacteria, the effect of important factors such as soil moisture, pH value, andthe soil temperature on the growth of microbial bacteria were observed. Under thefield conditions, the treatment of volatile petroleum hydrocarbons (isooctane) in thesoil spanned about105days, with the boundary point marked by the start time ofSVE/BV, this could be divided to be the biodegradation stage（from33to132days）and the the coupling SVE/BV and microbial remediation stag（efrom133to138days）.Using the experimental data from the biodegradation experiments, the degradationkinetic model parameters were obtained. The removal mechanism of contaminants inthe extraction emissions was studied via the single steady state soil extractingexperiments, and it was found that the removal of isooctane in the extractionemissions in the terms of time agreed well with the power function. The initial massweight of contaminant isooctane in the soil solid phase measured with the headspaceanalysis method was0.30%, and the contaminant removed percent at the end of thefirst stage was63.33%, while the contaminant removed percent at the end of the second stage was72.73％. The great performance of the coupling SVE/BV andmicrobial remediation technology that was applied to remove the volatile petroleumhydrocarbons was validated by the field experiments.Based on the equation of vapor flow of SVE/BV and the analysis of thebiodegradation kinetic model for the contaminated soil with petroleum, the masstransfer model of the coupling SVE/BV and microbial remediation for the treatmentof volatile petroleum hydrocarbons was proposed. Under steady state conditions, thecalculation results of the model of the single component and single extraction wellsystem agreed well with the field data, so the mathematical model that proposed inthis dissertation could be used to provide accurate data for the SVE/BV and microbialremediation treatment of field soil.The research results of this dissertation, especially the experimental andtheoretical conclusions of the research of the SVE/BV and microbial remediationin-situ treatment of volatile petroleum hydrocarbons, could be used as the basic dataand the reference for the pilot or field treatment of contaminated soil.