• 한국지반환경공학회 논문집
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• 제9권2호
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• pp.31-37
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• 2008

Diffused Aeration System (DAS) 기법은 휘발성 유기 화합물들을 포함하고 있는 지하수를 양수하여 반응조 내에서 폭기시킨 후, 액체 내에 존재하는 오염물질을 기체로 전이시켜 오염물질을 대기 중으로 배출시키는 정화법이다. 본 연구에서는 지하수 내 TCE 농도가 높은 2개 지역을 선정하여 3회에 걸쳐 DAS 기법의 적용성 평가 시험을 실시하였다. 반응조에는 각각 17.1, 44.8, 76.5 1/min의 속도로 공기를 주입하였으며, 시험 중 지하수 수질의 변화와 반응조에서 배출되는 TCE의 농도를 측정하였다. 처리 후 배출되는 기체의 농도를 측정한 결과, TCE 농도는 6~8 min 만에 최고 농도로 배출되었고, 시간이 지날수록 천천히 감소하는 모습이 관찰되었다. TCE의 농도 변화는 공기 유입 속도에 따라 매우 큰 변화를 보였다. 또한, 액체에서 기체로의 총괄물질전달계수 ($K_La$)를 산정한 결과, test 1, 2, 3에서 각각 0.444, 1.158, 1.836 1/hr였으며, 이로부터 공기 주입률이 빨라지면 DAS의 효율성이 높아짐을 정량적으로 확인할 수 있었다.

• 자원환경지질
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• 제35권6호
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• pp.581-588
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• 2002

• 한국토양환경학회지
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• 제3권2호
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• pp.53-60
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• 1998

주요 토양 및 지하수 오염물질인 가솔린에 대해 순수한 액상으로 존재할 경우와 오염된 토양으로 존재할 경우 물에 대한 용해거동을 각각 살펴보았다. 특히 휘발에 의한 가솔린 성분조성의 변화가 용출거동에 미치는 영향을 살펴보았다. 가솔린 오염토양을 공기흐름으로 통기시켰을 때 토양 중 용출거동의 변화는 공기 중 휘발농도의 변화양상과 비슷하게 나타나며 그 경향은 두 가지로 요약될 수 있다. 첫째 총량으로서의 가솔린 농도(TPH-GRO)는 휘발이 진행됨에 따라 급격히 감소하다가 75%정도의 무게감소 이후 점차적으로 감소하는 경향을 보이고 있다. 둘째 가솔린 개별성분의 농도는 일반적으로 증가하다가 감소하는 경향을 보이는데 분자량이 높을수록 상대적인 농도증가폭이 크고 최고농도에 도달하는데 많은 시간이 걸렸다. 한가지 특이한 점은 휘발이 진행될수록 공기 중 가솔린 농도가 용출 농도보다 훨씬 빠르게 감소한다는 점이다. 이것은 휘발에 의해 상당량의 가솔린이 제거되었을 경우 잔류가솔린으로 인한 위해성의 초점은 인근 대기오염보다도 지하수 오염에 맞추어져야 함을 시사한다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권6호
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• pp.48-55
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• 2013

This study aimed at characterizing unsaturated zone at the source zone area contaminated by DNAPL and investigating feasibility of soil vapor extraction (SVE). Five boreholes with three multi-level screens at the depth of 3.0~4.5 m, 5.5~7.0 m, and 8.0~12.0 m were installed at the source zone. Pneumatic tests were performed to determine the permeability of porous medium. Permeability was estimated to be 81.6 to 203.7 darcy, depending on the applied solutions, which was contradicted by grain size analysis of cored soil samples leading to 3.51 darcy. This is due to air flow through gravel pack during the early stage of pneumatic test. Pressure-drawdown curve in the late stage also well showed the leaky aquifer type, indicating air leakage to the ground. Air flow tests were also carried out to investigate air flow connectivity between multi-level wells, indicating that the horizontal air flow was well developed between the lower screens of the wells, not between the upper and middle screens due to the leakage to the surface. For the SVE test, there was no noticeable variation in TCE vapor concentration between three different test runs: 1. 8 hours daily for 5 days, 2. 24 hours together with air blowing at another well (BH1), 3. five consecutive days. Even for five-day consecutive test, total amount of removed TCE was estimated only to be as low as 46.5 g.

• 한국토양환경학회지
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• 제4권2호
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• pp.127-136
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• 1999

식물을 이용하여 토양이나 지하수 등의 매질로부터 오염물을 제거하는 기술인 phytoremediation은 지난 몇 년간 확용잠재성이 높은 환경복원기술로 많은 관심을 받아왔다. 본 연구에서는 현장조건을 모사한 그린하우스에서 이러한 phytoremediation에 의한 디젤로 오염된 토양의 정화효과를 조사하였다. 처리실험에 적합한 식물을 선정하기 위하여 인위적으로 디젤로 오염시킨 토양에서 증가에 따른 대상식물인 알팔파 옥수수, 피, 물피의 생장율 저하정도를 관측하여 내성이 강한 알팔파를 정화식물로 이용하였다. 디젤오염토양의 처리실험은 공기주입, 알팔파 파종, 공기주입과 알팔파 파종이 함께 적용된, PVC 파이프형태의 처리구에서 오염토양의 정화정도를 약 100일간 관측하였다. 칼럼 실험결과, 오염물의 제거속도에 기여하는 식물의 긍정적 효과가 관측되었으며 또한 지속적으로 토양내로 공기를 공급 하여줌으로써 Phytoremediation의 처리효율을 더욱 향상시킬 수가 있었다. 실험종료 후 각각의 처리구에서 토양 깊이별 미생물의 활성을 간접적으로 측정한 결과, 이러한 식물의 정화효과는 근권에 있는 토양미생물에게 유용한 뿌리 분비물을 지속적으로 제공함으로써 미생물의 활발한 번식 및 분해활동을 유지시켜 오염물의 분해를 더욱 촉진시키는 것으로 보인다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1998년도 공동 심포지엄 및 추계학술발표회
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• pp.81-85
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• 1998

In the present study, the design method of containment walls is proposed by utilizing an existing site. The selected remedy for the Source Area of Operable Unit 2 at Hill Air Force Base stipulated containment of the pure-phase trichloroethylene contamination. The in-place-mixed wall construction was selected because of the irregular topography, small area of the site, and the requirement to reach depths of greater than 90 feet below ground surface. Bench-scale compatibility studies were performed for the containment wall mix design on three commercial bentonite clays. The samples were subject to screening tests and long-term tests for evaluation of changed soil properties when exposed to the contaminated groundwater.

• 한국환경과학회지
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• 제15권6호
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• pp.513-525
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• 2006

In recent decades, biofiltration has been widely accepted for the treatment of contaminated air stream containing low concentration of odorous compounds or volatile organic compounds (VOCs). In this study, conventional biofilters packed with flexible synthetic polyurethane (PU) foam carriers were operated to remove toluene from a contaminated air stream. PU foams containing various amounts of pulverized activated carbon (PAC) were synthesized for the biofilter media and tested for toluene removal. Four biofilter columns were operated for 60 days to remove gaseous toluene from a contaminated air stream. During the biofiltration experiment, inlet toluene concentration was in the range of 0-150 ppm and EBRT (i.e., empty bed residence time) was kept at 26-42 seconds. Pressure drop of the biofilter bed was less than 3 mm $H_2O/m$ filter bed. The maximum removal capacity of toluene in the biofilters packed with PU-PAC foam was in the order of column II (PAC=7.08%) > column III (PAC=8.97%) > column I (PAC=4.95%) > column IV (PAC=13.52%), while the complete removal capacity was in the order of column II > column I > column III > column IV. The better biofiltration performance in column II was attributed to higher porosity providing favorable conditions for microbial growth. The results of biodegradation kinetic analysis showed that PU-PAC foam with 7.08% of PAC content had higher maximum removal rate ($V_m$=14.99 g toluene/kg dry material/day) than the other PU-PAC foams. In overall, the performance of biofiltration might be affected by the structure and physicochemical properties of PU foam induced by PAC content.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.85-92
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• 2015

PURPOSE. This study aimed to investigate the efficacy of cleaning solutions on saliva-contaminated zirconia in comparison to air-abrasion in terms of resin bonding. MATERIALS AND METHODS. For saliva-contaminated air-abraded zirconia, seven cleaning methods)-no contamination (NC), water-spray rinsing (WS), additional air-abrasion (AA), and cleaning with four solutions (Ivoclean [IC]; 1.0 wt% sodium dodecyl sulfate [SDS], 1.0 wt% hydrogen peroxide [HP], and 1.0 wt% sodium hypochlorite [SHC])-were tested. The zirconia surfaces for each group were characterized using various analytical techniques. Three bonded resin (Panavia F 2.0) cylinders (bonding area: $4.5mm^2$) were made on one zirconia disk specimen using the Ultradent jig method [four disks (12 cylinders)/group; a total of 28 disks]. After 5,000 thermocycling, all specimens were subjected to a shear bond strength test with a crosshead speed of 1.0 mm/minute. The fractured surfaces were observed using an optical and scanning electron microscope (SEM). RESULTS. Contact angle measurements showed that groups NC, AA, IC, and SHC had hydrophilic surfaces. The X-ray photoelectron spectroscopy (XPS) analysis showed similar elemental distributions between group AA and groups IC and SHC. Groups IC and SHC showed statistically similar bond strengths to groups NC and AA (P>.05), but not groups SDS and HP (P<.05). For groups WS, SDS, and HP, blister-like bubble formations were observed on the surfaces under SEM. CONCLUSION. Within the limitations of this in vitro study, some of the cleaning solutions (IC or SHC) were effective in removing saliva contamination and enhancing the resin bond strength.

• 한국산업보건학회지
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• 제10권1호
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• pp.18-31
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• 2000

A stack must be designed to 1) reduce or eliminate rainfall or snowfall into a industrial exhaust system, 2) minimize a resistance to flow, 3) maximize the vertical dispersion of the contaminated air and 4) minimize maintenance. The weather cone stacks and the elbow-type stacks are very popular in Korea. But they add some resistance to the exhaust system resulting in reduction of air flow rate, but also deflect the noxious contaminants downward in undiluted form. To solve these problems, ACGIH (American Conference of Governmental Industrial Hygienists) suggested the vertical discharge stack with concentric space between the upper stack with larger diameter and the lower stack with smaller diameter. The preliminary test showed that the vertical discharge stacks did not have the good rainfall protection. The reversed cone were newly devised to satisfy the requirements for the good stack. Subsequently, the amount of rain being penetrated through the stacks was measured while the stacks were simultaneously and naturally exposed to rain in the same area outside. Test results indicate that none of the stacks tested completely exclude rain. The efficiency of rainfall protection and the pressure loss coefficient were compared. The temporary conclusion was reached to the point that the reversed cone stack is the best one. Further research is underway.

• Advances in Energy Research
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• 제4권3호
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• pp.239-253
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• 2016

Air quality in hospitals has always concerned hospitals' health officials due to its dangerous particles and gases. Because of the importance of air conditioning in the operating room, a system must be embedded in operating rooms to direct the contaminated air outside, and inject fresh filtered air from outside back into the room. In this study, laminar flow air conditioning system is implemented in the operating room by slot linear diffusers and with the help of air curtain. For this, stimulation Computational Fluid Dynamic (CFD) was used due to its efficiency. The aim of the present study was to find a proper solution to overcome the unfavorable factors, namely, contamination, humidity, and also temperature, velocity and pressure inside the room. These factors were implemented with different values and then stimulated through FLUENT software program. Results showed that the aforementioned factors can be overcome using air curtain and slot linear diffusers.