• Journal of Soil and Groundwater Environment
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• v.17 no.1
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• pp.13-21
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• 2012

This study reports a surfactant-enhanced in-situ remediation treatment at a test site which is located in a hilly terrain. The leakage oils from a storage tank situated on the top of the hill contaminated soils and groundwater in the lower elevation. Sixteen vertical injection wells (11 m deep) were installed at the top of the hill to introduce 0.1-0.5 vol.% of non-ionic Tween-80 surfactant. The contaminated area that required remediation treatment was about $1,650\;m^2$. Two cycles of injecting surfactant solution followed by water were repeated over approximately 7.5 months: first cycle with 0.5 month of surfactant injection followed by 3 months of water injection, and second cycle with 1 month of surfactant followed by 3 months of water injection. The seasonal fluctuation in groundwater table was also considered in the selection of periods for surfactant and water injection. The results showed that the initial Total Petroleum Hydrocarbon (TPH) concentration of 1,041 mg/kg (maximum 3,605 mg/kg) was reduced significantly down to 76.6 mg/kg in average. After 2nd surfactant injection process finished, average TPH concentration of soils was reduced to 7.5% compared to initial concentration. Also, average BTEX concentration of soils was reduced to 10.8%. This resultes show that the surfactant enhanced in-situ remediation processes can be applicable to LNAPL contaminated site in field scale.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.356-359
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• 2003

Polycyclic aromatic hydrocarbons (PAHs) are representative hydrophobic organic carbons (HOCs). Surfactant-enhanced electrokinetic (EK) remediation is an innovative in-situ technology that can effectively remove HOCs from low-permeability soils. In this study, the electrokinetic remediation using Tergitol 15-S-12, a nonionic surfactant, was conducted for the removal of phenanthrene from kaolinite. Tergitol 15-S-12 was used at concentrations of 1.5, 2.0, 2.5 and 7.5 g/L to enhance the solubility of phenanthrene. When the surfactant solution was applied to EK system, high electrical potential gradient was maintained and the amount of electroosmotic flow decreased. Removal efficiency of phenanthrene was proportional to the concentration of Tergitol 15-S-12 because the solubility and mobility of phenanthrene was enhanced by surfactant micelle. Therefore, the suitable concentration of nonionic surfactant Tergitol 15-S-12 is expected to improve the removal efficiency of PAHs in EK remediation.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.23-28
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• 2000

초음파를 이용한 지반 세척의 효율을 높이기 위한 방법이 최근에 개발되었지만 그에 대한 연구는 아직 초기 단계인 실정이다. 본 연구는 초음파가 지반 정화에 미치는 영향에 대하여 실내 실험을 통해 고찰하였으며 특히 초음파 에너지의 강도, 시료의 종류 및 밀도, 그리고 수두의 변화가 지반 세척에 미치는 영향에 대하여 연구를 수행하였다. 상기의 연구 결과 지반 세척시 초음파가 세척 능력을 상당히 향상시키는 것으로 나타났으며 초음파에너지가 강할수록, 흐름 속도가 느릴수록 초음파의 효과가 크게 나타났다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.283-286
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• 2002

유류로 오염된 부지에 토양세정기법을 적용하기 위한 전 단계로, 실험실 규모의 컬럼실험을 통하여 pilot 규모 현장 적용을 위한 설계인자 및 최적 운전조건을 규명하고자 적정 세척제 종류와 농도, 배합비 및 세정용액 주입유량을 고찰하였다. 회분식실험 결과 POE$_{14}$와 SDS(1:1)를 1%로 적용한 흔합계면활성제의 효율이 가장 우수하였으나, 예비실험 결과 음이온계 계면활성제인 SDS는 미생물에 독성을 끼치는 경향이 있는 것으로 나타나 같은 농도에서 효율이 거의 유사한 POE$_{5}$와 POE$_{14}$ 혼합계면활성제를 이용하여 실험하였다. 선정된 혼합계면활성제를 적용하여 디젤 오염토양 세척능력을 검토한 결과 세척제 농도 1%까지는 효율이 증가하다가 1% 이상의 농도에서는 다시 감소하는 경향을 나타내었으며, 계면활성제 배합비는 1:1로 혼합하였을 경우 세척효율이 가장 우수하였다. 따라서 POE$_{5}$와 POE$_{14}$ (1:1) 1% 혼합계면활성제를 세척제로 선정하였다. 컬럼실험 결과, 주입 flux가 클수록 세정 제거된 총 유류의 양이 증가하였으며, 같은 pore volume의 세정용액 통과 시에는 flux가 작을수록 제거효율이 좋았다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.2
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• pp.96-109
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• 2021

Since terrestrial input plays a major role in coastal primary production, an understanding of land-ocean coupling (LOC) is key to understand coastal ecological changes. In this study, the LOC has been classified into three stages (i.e., the baseflow, plume event and residual flow). In order to characterize its pattern in Nakdong River estuary, multi-platform data were obtained from remote sensing (geostationary ocean color image (GOCI)), in-situ measurement (marine environment information system (MEIS)), on-site measurement (discharge data and meteorological data). The MEIS data were grouped into three stages of LOC using principal component analysis (PCA), and the LOC (2013 ~ 2018) was examined at each stage using multi-platform data. In the Nakdong River estuary, the maximum value of chlorophyll-a (chl-a) was unexpectedly appeared during the plume event. It is assumed that there was no significant increase in turbidity, expected during the typical plume event, together with the weak flushing effect, caused the enhanced phytoplankton growth. Compared with other estuaries, LOC is common in estuaries affected by freshwater inflow, but LOC has different pattern depending on the size of the plume. While estuaries that form small plumes of about 10 km (low freshwater discharge and weak flushing effect) observed high chl-a in the plume event because the phytoplankton can response to the increased nutrient more rapidly. estuaries that form large plumes of more than 100 km est (high freshwater discharge and strong flushing effect) follow the typical LOC pattern conceptualized in this study (high chl-a in the residual flow).

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.91-96
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• 2001

Restoration of contaminated soils to an environmentally acceptable condition is important. One of the newer techniques in soil remediation is a method based on electrokinetic phenomena in soils. The technology uses electricity to affect chemical concentrations and water flow through the pores of soils. An important advantage of electrokinetic soil remediation over other in-situ processes such as soil flushing is the capability of control over the movement of the contaminants. Because the migration of the contaminants is confined by the electric field, there is little dispersion outside the treatment zone. Furthermore, the process is effective for soils with low and variable permeability. In the present study, the distributions of cadmium in the electrokinetic processing of kaolinite under the condition of constant applied voltage are investigated. Cadmium accumulates near the cathode without reducing the diffusion of hydroxide ion into the soil. In keeping the catholyte pH at neutrality, cadmium migrates toward the cathode without any accumulation of cadmium near the cathode and is successfully removed at the cathode reservoir. It was also found that the progress of electrokinetic processing of cadmium could be gasped to a certain extent by monitoring the local voltage and the current density.

• Journal of Soil and Groundwater Environment
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• v.18 no.6
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• pp.8-17
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• 2013

The contamination of chlorinated ethenes at an industrial complex, Wonju, Korea, was examined based on sixteen rounds of groundwater quality data collected from 2009 to 2013. Remediation technologies such as soil vapor extraction, soil flushing, biostimulation, and pumping-and-treatment have been applied to eliminate the contaminant sources of trichloroethylene (TCE) and to prevent the migration of TCE plume from remediation target zones. At each remediation target zone, temporal monitoring data before and after the application of remediation techniques showed that the aqueous concentrations of TCE plume present at and around the main source areas decreased significantly as a result of remediation technologies. However, the TCE concentration of the plumes at the downstream area remained unchanged in response to the remediation action, but it showed a great fluctuation according to seasonal recharge variation during the monitoring period. Therefore, variations in the contaminant flux across three transects were analyzed. Prior to the remediation action, the concentration and mass discharges of TCE at the transects were affected by seasonal recharge variation and residual DNAPLs sources. After the remediation, the effect of remediation took place clearly at the transects. By tracing a time-series of plume evolution, a greater variation in the TCE concentrations was detected at the plumes near the source zones compared to the relatively stable plumes in the downstream. The difference in the temporal profiles of TCE concentrations between the plumes in the source zone and those in the downstream could have resulted from remedial actions taken at the source zones. This study demonstrates that long term monitoring data are useful in assessing the effectiveness of remediation practices.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.204-205
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• 2011

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is a most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. For best performance of thin film silicon solar cell, the dopant profiles at p/i and i/n interfaces need to be as sharp as possible. The sharpness of dopant profiles can easily achieved when using multi-chamber PECVD equipment, in which each layer is deposited in separate chamber. However, in a single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of a single-chamber PECVD system in spite of the advantage of lower initial investment cost for the equipment. In order to resolve the cross-contamination problem in single-chamber PECVD systems, flushing method of the chamber with NH3 gas or water vapor after doped layer deposition process has been used. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. A single-chamber VHF-PECVD system was used for superstrate type p-i-n a-Si:H solar cell manufacturing on Asahi-type U FTO glass. A 80 MHz and 20 watts of pulsed RF power was applied to the parallel plate RF cathode at the frequency of 10 kHz and 80% duty ratio. A mixture gas of Ar, H2 and SiH4 was used for i-layer deposition and the deposition pressure was 0.4 Torr. For p and n layer deposition, B2H6 and PH3 was used as doping gas, respectively. The deposition temperature was $250^{\circ}C$ and the total p-i-n layer thickness was about $3500{\AA}$. In order to remove the deposited B inside of the vacuum chamber during p-layer deposition, a high pulsed RF power of about 80 W was applied right after p-layer deposition without SiH4 gas, which is followed by i-layer and n-layer deposition. Finally, Ag was deposited as top electrode. The best initial solar cell efficiency of 9.5 % for test cell area of 0.2 $cm^2$ could be achieved by applying the in-situ plasma cleaning method. The dependence on RF power and treatment time was investigated along with the SIMS analysis of the p-i interface for boron profiles.

• Tunnel and Underground Space
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• v.22 no.4
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• pp.257-265
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• 2012

In this study, a series of CFD (Computational Fluid Dynamics) simulations carried out to evaluate the optimum design model of the internal flow path of drill bit. The Star-CCM+ code was adopted to simulate the multi-phase discharge flow of rock particles and flushing air during a drilling process. The input parameters for the flow simulation of rock particles and air were obtained from the in-situ drilling test results. After the three design factors were determined, the experimental design method (Taguchi method) was utilized to evaluate the optimum value of each factor.