• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.382-388
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• 2005

Soil vapor extraction(SVE) is an effective and cost efficient method of removing volatile organic compounds(VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. Prefabricated vertical drains(PVDs) have been used for dewatering fine-grained soils for more than 25 years. Incorporating PVDs in and SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. The objective of the work described herein was to effectively incorporate PVDs into a SVE remediation system and to demonstrate a PVDs enhanced SVE system at full scale. The finding from this research will facilitate the design of field PVD-SVE systems in terms by providing insight into the optimal spacing between PVDs, the radius of influence of the wells and the flow rates to be used to capture and extract gas phase contaminants.

• Journal of the Korean Geosynthetics Society
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• v.6 no.3
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• pp.9-16
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• 2007

Soil vapor extraction (SVE) is an effective and cost efficient method of removing volatile organic compounds (VOCs) and petroleum hydrocarbons from unsaturated soils. Incorporating PVDs in an SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. With this approach, the real bounded system is replaced for the purposes of analysis by an imaginary system of infinite areal extent. The boundary conditions for the contaminant remediation model test include constant head and no flow condition. Due to these parallel boundaries conditions, image wells should be developed in order to maintain the condition of no flow across the impermeable boundary. It is also assumed that the flow is drawdown along the constant head boundary condition. The factors contributing to the difference between the theoretical and measured pressure heads were also analyzed. The flow factor increases as the flow rate is increased. The flow rate is the most important factor that affects the difference between the measured and theoretical pressure heads.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.267-274
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• 2011

The environmental impacts of 95% remediation of a total petroleum hydrocarbon-contaminated soil were evaluated using life cycle assessment (LCA). LCA of two remediation systems, soil vapor extraction (SVE) and biopile, were conducted by using imput materials and energy listed in a remedial system standardization report. Life cycle impact assessment (LCIA) results showed that the environmental impacts of SVE were all higher than those of biopile. Prominent four environmental impacts, human toxicity via soil, aquatic ecotoxicity, human toxicity via surface water and human toxicity via air, were apparently found from the LCIA results of the both remedial systems. Human toxicity via soil was the prominent impact of SVE, while aquatic ecotoxicity was the prominent impact of biopile. This study also showed that the operation stage and the activated carbon replacement stage contributed 60% and 36% of the environmental impacts of SVE system, respectively. The major input affecting the environmental impact of SVE was electricity. The operation stage of biopile resulted in the highest contribution to the entire environmental impact. The key input affecting the environmental impact of biopile was also electricity. This study suggested that electricity reduction strategies would be tried in the contaminated-soil remediation sites for archieving less environmental impacts. Remediation of contaminated soil normally takes long time and thus requires a great deal of material and energy. More extensive life cycle researches on remedial systems are required to meet recent national challenges toward carbon dioxide reduction and green growth. Furthermore, systematic information on electricity use of remedial systems should be collected for the reliable assessment of environmental impacts and carbon dioxide emissions during soil remediation.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.9-18
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• 2007

Soil vapor extraction (SVE) is an effective and cost efficient method of removing volatile organic compounds (VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. Incorporating PVDs in an SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. The objective of the research described herein was to effectively incorporate PVDs into a SVE remediation system. The test results show that the gas permeability was evaluated for four different equivalent diameters, increasing the equivalent diameter results in a decrease in the calculated gas permeability. It was found that the porosity for the dry condition was greater than that of the wet condition and will allow flow rate for the same vacuum flow, offering a low resistance to the air flow.

• Journal of Environmental Science International
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• v.17 no.1
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• pp.97-105
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• 2008

This study examined the contaminated soils with an indicator of TPH using SVE (Soil Vapor Extraction) and biological treatments. Their results are as follows. Water content in the polluted soils slowly decreased from 15% during the initial experimental condition to 10% during the final condition. Purification of polluted soils by Bioventing system is likely to hinder the microbial activity due to decrease of water content. Removal rate of TPH in the upper reaction chamber was a half of initial removal rate at the 25th day of the experiment. The removal rate in the lower reaction chamber was 45% with concentration of 995.4 mg/kg. When the Bioventing is used the removal rate at the 14th day of the experiment was 53%, showing 7 day shortenting. Since the Bioventing method control the microbial activity due to dewatering of the polluted soil, SVE method is likely to be preferable to remove in-situ TPH. The reactor that included microbes and nutrients showed somewhat higher removal rate of TPH than the reactor that included nurtients only during experimental period. In general, the concentration showed two times peaks and then decreased, followed by slight variation of the concentration in low concentration levels. Hence, in contrast to SVE treatment, the biological treatment tend to show continuous repetitive peaks of concentration followed by concentration decrease.

• Journal of Soil and Groundwater Environment
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• v.20 no.1
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• pp.1-6
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• 2015

The objectives of this study were to calculate the radius of influence (ROI) of well for an air-sparging (AS)/soil vapor extraction (SVE) system and to evaluate the applicability of the system applied for the remediation of the petroleum contaminated rail site. For air permeability test, three monitoring wells were installed at a location of 1.3 m, 2.3 m, 3.0 m from the extraction well. And the pressure of each monitoring well was measured by extracting air from the extraction well with the pressure and flow of $(-)2,600mmH_2O$ and $1.58m^3/min$. The ROI for an extraction well was calculated as 4.31 m. Air was injected into the injection well with the pressure and flow of $3,500mmH_2O$ and $0.6m^3/min$ to estimate the radius of influence for oxygen transfer. Oxygen concentrations of air from three monitoring wells were measured. The ROI of an injection well for oxygen transfer was calculated as 3.46 m. The 28 extraction wells and 19 injection wells were installed according to the ROI calculated. The AS/SVE system was operated eight hours a day for five months. The rail site was contaminated with the petroleum and concentrations of benzene, toluene, and xylene were over the 'Worrisome Standard' of the 'Soil Environment Conservation Act'. The contaminated area was estimated as $732m^2$ and contaminants were dispersed up to (-)3 m from the ground. During the operation period, soil samples were collected from 5 points and analyzed periodically. With the AS/SVE system operation, concentrations of benzene, toluene, and xylene were decreased from 7.5 mg/kg to 2.0 mg/kg, from 32.0 mg/kg to 23.0 mg/kg, from 35.5 mg/kg to 23.0 mg/kg, respectively. The combined AS/SVE system applied to the rail site contaminated with volatile organic compounds (VOCs) exhibited a high applicability. But the concentration of contaminants in soil were fluctuated due to the heterogeneous of soil condition. Also the effect of the remediation mechanisms was not clearly identified.

• Journal of Soil and Groundwater Environment
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• v.9 no.2
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• pp.28-40
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• 2004

Box experiments were performed to evaluate the removal efficiency of SVE (soil vapor extraction) for gasoline in soil. An activated carbon sorption tower and a biofilter were operated as post-treatment processes to remove VOCs extracted from extraction wells of SVE. An acrylic resin box (65 cm${\times}$20 cm${\times}$30 cm) was used to make artificial soil layers and two injection wells and one extraction well were built for SVE process in the box. Gases from extraction wells flew into the activated carbon sorption tower or the biofilter. Gasoline concentrations of VOCs emitted from the extraction well were compared with those after post treatments. More than 92% of initial gasoline mass in soil were removed by SVE within few days, suggesting that SVE is very available to remove VOCs from contaminated soils. To treat VOCs from extraction wells of SVE, an activated carbon sorption tower and a biofilter were attached to SVE process and their gasoline removal efficiencies were measured. These post treatment systems lowered gasoline concentrations to below 1.0 ppm within few days. Average remediation efficiency was 98% of gasoline for the activated carbon sorption tower and 84.1% for the biofilter. The maximum removal capacity of a biofilter was 10.7 g/L/hr, which was ten times higher than general biofilter removal capacity. Results from the study suggest that the activated carbon sorption tower and the biofilter would be available for the post treatment process to remove VOCs generated from SVE process.

• Journal of the Korean Geosynthetics Society
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• v.7 no.4
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• pp.1-8
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• 2008

Soil vapor extraction (SVE) is an effective and cost efficient method of removing volatile organic compounds (VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. The aim of this study is to investigate numerically the performance of a prefabricated vertical drain (PVD) as a SVE well, and the pattern of the induced air flow. A validated numerical model for a single PVD extraction well is developed based on the result of a well-designed laboratory model test. The validity of the simple analytical approach to determine air permeability based on the results of model tests is also discussed.

• Journal of Korea Soil Environment Society
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• v.4 no.3
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• pp.3-15
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• 1999

This paper includes the basic experimental results performed for developing an innovative and technologically feasible process wherein gaseous ozone, a powerful oxidant. is injected directly into vadose zone by which in-situ chemical degradation of semi- or, non-volatile petroleum product such as diesel fuel is derived. As ozone gas injected continuously(50mL/min, 119.0$\pm$6.1mg/L) into soil packed columns artificially contaminated with diesel fuel(initial concentration 1,485mg-DRO/kg/soil), the removal rates at the inlet and outlet point of 14hrs-operated column are 87.9% and 100.0%, respectively. On the other hand, soil vapor extraction system showed less than 30% of removal rates of residual diesel both at the inlet and outlet samples under the same experimental conditions which confirms the limited treatability of SVE in diesel contaminated soil.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.35-43
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• 2005

Bioslurping combines the three remedial approaches of bioventing, vacuum-enhanced free-product recovery, and soil vapor extraction. Bioslurping is less effective in tight (low-permeability) soils. The greatest limitation to air permeability is excessive soil moisture. Optimum soil moisture is very soil-specific. Too much moisture can reduce air permeability of the soil and decrease its oxygen transfer capability. Too little moisture will inhibit microbial activity. So Modified Fenton reaction as chemical treatment which can overcome the weakness of Bioslurping was experimented for simultaneous treatment. Although the diesel removal efficiency of SVE process increased in proportion to applied vacuum pressure, SVE process was difficulty to remediation quickly semi- or non-volatile compounds absorbed soil strongly. And SVE process had variation of efficiency with distance from the extraction well and depth a air flow form of hemisphere centering around the well. Below 0.1 % hydrogen peroxide shows the potential of using hydrogen peroxide as oxygen source but the co-oxidation of chemical and biological treatment was impossible because of the low efficiency of Modified Fenton reaction at 0.1 % (wt) hydrogen peroxide. NTA was more efficiency than EDTA as chelating agent and diesel removal efficiency of Modified Fenton reaction increased in proportion to hydrogen peroxide concentration. Hexadecane as typical aliphatic compound was removed less than Toluene as aromatic compound because of its structural stability in Modified Fenton reaction. What minimum 10% hydrogen peroxide concentration has good remediation efficiency of diesel contaminated groundwater may show the potential use of Modified Fenton reaction after bioslurping treatment.