Study On Soil Vapor Extraction And Biosparging Of Diesel Fuel In Polluted Underground Environment

Oil is one of the necessary energy of modern industry development, With therapid social and economic development, oil extraction and usage has become moreextensive, however, the mining transport and use of improper operation andaccidents, making the problem of oil pollution become increasingly prominent.Once the oil leaked into the underground environment, a direct result is thecontamination of the vadose zone, with the migration and transformation ofpollutants, it will seriously affect the safety of groundwater.There are many technologies of control and restore the oil pollution, butcompared to ectopic remediation, in-situ remediation more and more aroused theenvironmental researchers, because of its efficient, economic and smallenvironmental destructive and other advantages.The topics chosen for the twomethods, typical soil vapor extraction and biosparing, studied the migration ofdiesel contaminants in the vadose zone, the influence factors of diesel pollution inthe vadose zone of the soil vapor extraction, and biosparging operation repaireddiesel-contaminated aquifers.Through one-dimensional sand column leaching experiments by diesel fuel invadose zone to simulate in the migration process, the results showed that:（1） Different media for the interdiction capacity of diesel pollutants is different,from the test interdiction capacity point of view, fine sand> medium sand>coarsesand.（2） Different levels of pollution migration of contaminants also have a greatimpact in the same amount of leaching water conditions,10g·kg^-1concentration ofcontaminants had stronger migrative ability than6g·kg^-1concentration of contaminants.（3） The migration of the contaminants in the soil gradually increased with thetime, and with increaseing leaching time, the amount of contaminants tended to bestable.（4） GC-MS analysis of result showed that water and soil samples in earlyleaching water samples pollutants are toluene, methyl naphthalence, indane/indenephenol, benzyl alcohol and alkanens. For major pollution in the late leaching soilcomposition is C₁₀～C₂₃, those above C₁₅are the main ingredients.A series of simulations were conducted to study: SVE technology and itsinfluencing factors, the results showed that:（1） The extraction rate has a great influence on the results. Extraction rateincreased, the removal of contaminants efficiency was also improved, but theincrease in the amount of contaminants removal efficiency and extraction rateincrease were not proportional. Compared to the extraction rate of0.3m³·h^-1, therate of0.4m³·h^-1removal was decreased.（2） Media of particle size have a significant impact on the treatment effect ofSVE, Coarse sand of TPH（Total Petroleum Hydrocarbon, hereinafter referred to asTPH）removal efficiency higher than the medium sand of that.（3） Media moisture content has a significant impact on the treatment effect ofSVE. TPH elimination rate in the moisture content1%coarse sand medium isbigger than TPH elimination rate in the moisture content12%coarse sand.（4） After the end of the extraction, water content of coarse sand was greatlydecreased, indicated that the extraction was not only conducive to the removal ofdiesel components, evaporation of moisture removal was also obvious.（5） Different ventilation, intermittent ventilation efficiency is less thancontinuous ventilation, but it can effectively save energy. If there is not limite totime of repair contaminated sites, we may be considered intermittent ventilation.（6） The higher levels of contaminants within a certain range, the use of SVE technology to remove contaminants required longer time, but the low content ofdiesel5g.kg^-1of repairing effectiveness was not as good as the content of15g.kg^-1of repairing effectiveness.With the use of two-dimensional sand tank experiment, a dynamic simulation ofaquifer carrier of diesel pollution is carried out, by adding microorganisms andnutrients to enhance biological remedition-BS, the results showed that:（1） In the process of aquifer polluted by diesel, the concentration of TPH inthe aquifer above the simulated slot corresponding to the leakage point is themaximum, and diesel fuel accumulates at the top of the simulated slot. Leakage ismore serious pint about30cm around the diesel pollution levels in the region, themaximum concentration of TPH can be over40mg.L^-1, In the late pollution,Non-Aqueous Phase Liquid（hereinafter referred to as NAPL） can be found existingin the water samples taken from the sample collection around the leakage point.（2） Diesel lateral migration is notable, and there are a range of pollutionsources of pollution upstream, in the risk assessment of diesel contaminatedaquifers, we should take full account of the migration regularity. In dieselcontaminated groundwater, the distance and orientation changes from the point ofthe leakage have a great influence on the concentration of pollutants, the fatheraway from the leakage point, the speed of the pollutants concentrations movedwere slower.（3） Set the aeration well40cm downstream of the diesel pollution of aquiferpollution sources, after the diesel pollution in the aquifer region, the fixed aerationfixed aeration well aerated location in the bottom of the well along the5cmdistance of0.5m³·h^-1aeration flow, While added100ml bacterium suspension and1L of nutrient solution,0.1g·L^-1yeast extract and0.2g·L^-1peptone in aeration well.through cumulative aeration45min, TPH contamination in the aquifer significantlyreduced, and TPH were not detected in30cm region besides the circular well,while the TPH concentration of the sources was decreased to5.0mg·L^-1from the original concentration of40.0mg·L^-1. The research results BS process has asignificant effect on the repair of diesel contaminated aquifer.