• Air Cleaning Technology
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• v.26 no.2
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• pp.41-51
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• 2013

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.

• Journal of Korea Far Infrared Association
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• s.24
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• pp.32-37
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• 2005

공기이온에 관한 연구는 많은 분야의 연구원 참여에 의해 폭넓게 알려져, 반세기에 이르는 번영의 역사를 쌓아 왔지만, 불가사의하게도 현재, 가장 중요한 적용분야인 보건 분야에서 위기를 맞고 있다. 20세기 초, 대기 중에 전하를 띤 입자의 존재가 관찰된 이래, 공기 이온의 성질을 문제로 한 기초적 연구가, 간단한 공기이온계측기 보급과 함께, 물리학자, 생물학자, 의학자의 협력 하에 1930년대 이후 활발히 이루어져, 공기이온의 위생적ㆍ치료적 가치에 대한 풍부한 정보를 얻을 수 있게 되었다. 어찌되었든 이온화환 공기 속에서는 생활할 수 없는 것이 확실해져, 어떤 농도의 공기이온은 사람 및 동물의 생체에 유익한 작용을 하고, 대용량 공기이온은 치료에 적용가능하지만, 농도의 여하에 관계없이, 양이온이 음이온에 비해 2~3배 우세하면, 신체의 상태를 악화시켜며, 또한 공조설비와 필터류는 모두 이온화작용을 나타내는 것도 밝혀졌다. 청정한 공기를 이온화하는 것은 산소, 탄산가스, 약용물질분자를 활성화시키지만, 오염된 공기의 이온화는 유독한 불순물의 독성을 증가시키는 점도 지적되었다.

• Membrane Journal
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• v.25 no.3
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• pp.276-286
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• 2015

The effects of relaxation and backwashing on fouling in ultrafiltration were investigated using full-scale membrane bioreactors (MBRs) which operated at a constant flux of 30 LMH. This paper also estimated the feasibility of using intermittent aeration strategies for minimizing the hydraulic resistance to filtration in comparison with the continuous aeration for running MBRs. Multiple cycles of filtration (14.5 min each) and relaxation (0.5 min each) were repeated. Similarly, a backwash was conducted by replacing a relaxation after each filtration cycle for the comparative performance test. The attached cake thickness on the membrane rapidly increased, caused by subsequent no aeration leading to easier combining with gel layer and the formation of heterogeneous layer on the membrane surface. During periodic backwashing, it is expected that gel and thin cake layer might sufficiently be removed by heterogeneous layer. After periodic backwashing, subsequent cake layer formation during time of no aeration was rapid than frequent no aeration, acting as a prefilter and preventing further irreversible fouling. Based on the Pearson correlation analysis, overall period fouling (dTMP/min) and average of all cycles (dTMP/min) were strongly correlated with the on-off period of aeration for operating MBRs.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.61-68
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• 2006

Soil washing techniques coupled with high pressure air jet were applied for diesel-contaminated soils sampled by an underground oil reservoir of which the initial total petroleum hydrocarbon (TPH) ($2,828{\pm}206\;mg/kg$) exceeded 5 times of current standard level (500 mg/kg) regulated by the Soil-Environment Conservation Law. Through several tests, we found that the position of impeller has a critical impact for washing efficiencies. The highest washing efficiency was obtained at an oblique angle (30 degree) for the impeller and optimized mixing speed (300 rpm) that could have high shearing forces. Considered economical and feasible aspects, the optimum mixing time was 10 min. Rate constants of TPH removal derived from the first-order equation were not linearly increased as mixing speed increased, indicating that mechanical mixing has some limits to enhance the washing efficiencies. Application of high-pressure air jet in washing process increased the washing efficiency. This increase might be caused by the fact that the surface of micro-air bubbles strongly attached hydrophobic matters of soil particles. As the pressure of air jet increased, the separation efficiencies of TPH-contaminated soil particles increased. In the combined process of high-pressure air jet and mixing by impeller, the optimum mixing speed and air flow-rate were determined to be 60 rpm and $2\;kg/cm^2$, respectively. Consequently, the washing technique coupled with high-pressure air jet could be considered as a feasible application for remediating petroleum-contaminated soils.

• Membrane Journal
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• v.25 no.3
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• pp.256-267
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• 2015

The goal is to compare two different aeration strategies for a pilot scale operation of submerged microfiltration with respect to the minimization of membrane fouling. A constant aeration (65 L/min) was examined parallel with a step-wise increase in airflow rate (40 to 65 L/min). The airflow rate was stepped to a higher rate every 5 min and the step-aeration cycles were repeated at regular intervals of 15 min. The comparative filtration runs were conducted with synthetic water containing powdered activated carbon (~10 g/L) and/or kaolin (~20 g/L) at a constant flux of 80 LMH. The extent and mechanisms of fouling in the microfiltration were identified by determining hydraulic resistance to filtration and the fouling reversibility after cleaning. Results showed that the step-aeration effectively alleviated fouling in the microfiltration of synthetic water compared to when using constant aeration. A substantial decrease in fouling was achieved by combining with coagulation using aluminum salts regardless of the aeration strategies. The constant aeration resulted in increased pore blocking likely due to increased accumulation of particles on the surface of membrane.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.249-250
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• 2000

현대인들은 24시간 중 70∼80%의 시간을 실내에서 보내고 있는 것으로 보고되고 있으며, 1980년대 이후 실내에서의 일일 노출시간 증가, 한정된 공간에서의 오염된 공기의 지속적 순환, 에너지 절감 시스템에 의한 건물의 밀폐화에 따른 오염농도의 누적현상, 다양한 건축자재 및 생활 인테리어 용품의 사용으로 인한 실내 오염원의 존재 등으로 실내 공기질 악화에 따른 건강 영향에 대해 관심이 고조되기 시작하였다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.369-370
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• 2000

동북아시아에서 화석연료의 연소로부터 배출되는 인위적 대기오염물질의 증가는 심각한 문제로 대두되고 있다. 우리 나라의 경우는 도시화, 인구 밀집과 자동차의 증가로 인한 대기오염물질 배출은 대도시에서 공기질 저하를 야기하고 있다. 특히, 서울 지역은 가시도(Visibility), 오존 등의 심각한 공기오염문제를 경험하고 있다. 이러한 대기오염은 국지적 기상변화에 따라 발생하는 도시형 스모그나 안개과 밀접한 관계가 있는 것으로 추정되며, 발생시 에어로졸의 특성변화가 예상되고 있으나, 스모그나 안개 발생시 에어로졸의 특성이나 고도 분포에 대한 연구는 미흡한 실정에 있다. (중략)

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.76-79
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• 2005

대수층 폭기법(aquifer air sparging)은 대수층에 가압공기를 주입하여 휘발성 유기오염물질을 제거하는 지반환경복원 기술의 하나이다. 본 연구는 전통적인 지하 대수층 폭기기술 시행에 있어서 특정층에 미리 수용액상 계면활성제를 수평방향으로 도입함으로써 오염물질이 실제로 존재하는 층에 선택적으로 폭기 되도록 하여 최소한의 공기량으로 제거 효율을 극대화 하는 기술을 개발하는 것을 목적으로 한다. 본 연구에서는 균일질 모래로 충진된 2차원 상자 모델을 사용하였으며, 표면장력 조절을 위하여 저농도(100mg/L) 음이온계 계면활성제(sodium dodecyl benzene sulfonate) 수용액이 사용되었다. 실험은 계면활성제가 처방되지 않은 경우, 공기도입부 근처에 계면활성제 용액이 도입된 경우, 공기도입부와 토양표면의 중간부분에 계면활성제 용액이 도입된 경우의 세 가지 방법으로 실시되었다. 실험 결과, 계면활성제가 도입된 경우는 투입되지 않은 경우에 비하여 최고 5배에 해당하는 폭기영향권의 확대가 관찰되었으며 폭기영향권이 계면활성제가 도입된 수평층을 중심으로 형성되어 이 부분에 집중되어 존재하는 오염물질의 제거에 매우 유리할 수 있다는 점이다. 대수층 도입공기의 수평확산을 유도하는 기술로 본 연구는 기존의 대수층 폭기 복원기술의 효율을 획기적으로 개선할 수 있을 것으로 기대된다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.503-508
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• 2003

Heating, Ventilation and hir Conditioning (HVAC) system in nuclear facility should be equipped and constructed more stable and allowable than that in common facility. The purpose of HVAC system is the maintenance of optimum working environment, the protection of worker against a contaminated air and the prevention of atmospheric contamination due to a outward ventilation, etc.. The basic scheme of a safety operation of nuclear facility is to prevent the atmospheric contamination even in low level. The adaptability of HVAC system should be taken into account in the design stage so that it is possible to modify the system which is in operation. In this study, the design requirements of HVAC system in nuclear facility and the HVAC systems in foreign countries are reviewed, and the results can be utilized in the design of HVAC system in nuclear facility.