• Title/Summary/Keyword: fouling control

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Numerical Simulation of Three Dimensional Fluid Flow Phenomena in Cylindrical Submerged Flat Membrane Bioreactor for Aeration Rate (원통 침지형 평막 생물반응기 내 산기량에 따른 3차원 유동현상에 관한 수치모사)

  • Kim, Dae Chun;Chung, Kun Yong
    • Applied Chemistry for Engineering
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    • v.25 no.4
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    • pp.401-408
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    • 2014
  • In membrane bio-reactor (MBR), the aeration control is one of the important independent variables to decrease fouling and to save energy with shear stress change on the membrane surface. The paper was carried out for numerical simulation of 3-dimensional fluid flow phenomena of the cylindrical bioreactor with submerged flat membranes equipped in the center and supplied the air from the bottom by using the COMSOL program. The viscosity and temperature of solution were assumed to be constant, and the specific air demand based on permeate volume ($SAD_p$) defined as scouring air per permeate rates was used as a variable. The calculated CFD velocities were compared with those of the velocity meter measurement and video image analysis, respectively. The results were good agreement each other within 11% error. For fluid flow in the reactor the liquid velocity increased rapidly between the air diffuser and membrane module, but the velocity decreased during flowing of the membrane module. Also, the velocity increased as it was near from the reactor wall to the central axis. The calculated shear stress on the membrane surface showed the highest value at the center part of the module bottom side and increased as aeration rate increased. Especially, the wall shear stress increased dramatically as the aeration rate increased from 0.15 to 0.25 L/min.

Appropriate Technology and Field Application of Non-powered Water Purification System Using Nanofiber Membrane (나노섬유 멤브레인 기반 무동력 정수 시스템의 적정기술 및 현장 적용)

  • Lee, Jin;Yun, Byeong Gweon;Han, Kyoung Gu;Lee, Seung Hoon;Kim, Cheol Hyeon;Kim, Chan;Lee, Yunho;Lee, Dongwhi;Lee, Seunghyeok;Kim, Kyoung-Woong
    • Journal of Appropriate Technology
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    • v.7 no.1
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    • pp.72-81
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    • 2021
  • Gravity-driven membrane (GDM) filtration system based on the nanofiber membrane was investigated. This system can be operated with little energy demand due to a gravitational pressure-driven filtration and biological fouling control strategy. Moreover, the optimal module configuration based on the high permeance of nanofiber membrane can provide a significantly high water productivity. In order to evaluate its applicability potential, the pilot-scale (3000-5000 L/day) systems with nanofiber membranes were operated in developing countries (Kiribati and Tuvalu). Our results showed that the 14-92 L/(m2×h) of the permeate flux was determined indicating a stabilized water productivity. In addition, the permeate water indicated a high removal rate (more than 99.99%) of turbidity and bacteria. Consequently, the system can provide a stabilized water production with safe permeate water quality during long-term operation. These findings exemplify an effective approach to decentralized drinking water treatment for developing countries.

Surface Patterning and Characterization of Food Packaging Films Using Femtosecond Laser (펨토초 레이저를 이용한 식품포장 필름의 표면 패터닝 및 특성)

  • Youngjin Cho
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.29 no.2
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    • pp.111-118
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    • 2023
  • In this study, the feasibility of laser patterning on the surface of food packaging polymer film was confirmed, and the surface patterning process conditions of femtosecond laser were established. In addition, it was proved that the surface properties of the film can be changed and controlled through the fabrication of various patterned films on the surface of food packaging films such as HDPE, PP, and PET. Various patterned surfaces, including large-scale circular patterns induced by a single femtosecond laser pulse, roughness patterns achieved by overlapping single pulses by 30%, straight line patterns, roughness patterns obtained by overlapping straight line patterns, and grid patterns formed by intersecting straight line patterns were fabricated. The characteristics of the patterned HDPE, PP, and PET films, based on the surface pattern structure and size, were analyzed using SEM, AFM, and contact angle measurements. Compared to the surface of each control film without femtosecond laser patterning, the contact angles of the surfaces of large-area circular patterning HDPE and PP films, large-area roughness patterning HDPE and PP films by overlapping 30% of single pulses, and large-area roughness patterning PET film by overlapping rectilinear patterning were in the range of 27.1-37.5 degree. This indicated that the HDPE, PP, and PET films became more hydrophilic after patterning. On the other hand, the HDPE film patterned with a large-scale grid pattern exhibited a contact angle of 120.4 degree, indicating that the HDPE film became more hydrophobic after patterning. Therefore, films that have been changed to hydrophilic surfaces through patterning can be used in anti-fouling applications where proteins, cells, viruses, and other food materials do not adhere or are easily detached. In addition, if a superhydrophobic surface of 150 degrees or more is fabricated through more precise lattice patterning in the future, it will be possible to use it for superhydrophobic surface applications such as self-cleaning.

Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.7
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

Adhesion Characteristics and the High Pressure Resistance of Biofilm Bacteria in Seawater Reverse Osmosis Desalination Process (역삼투 해수담수화 공정 내 바이오필름 형성 미생물의 부착 및 고압내성 특성)

  • Jung, Ji-Yeon;Lee, Jin-Wook;Kim, Sung-Youn;Kim, In-S.
    • Journal of Korean Society of Environmental Engineers
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    • v.31 no.1
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    • pp.51-57
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    • 2009
  • Biofouling in seawater reverse osmosis (SWRO) desalination process causes many problems such as flux decline, biodegradation of membrane, increased cleaning time, and increased energy consumption and operational cost. Therefore biofouling is considered as the most critical problem in system operation. To control biofouling in early stage, detection of the most problematic bacteria causing biofouling is required. In this study, six model bacteria were chosen; Bacillus sp., Flavobacterium sp., Mycobacterium sp., Pseudomonas aeruginosa, Pseudomonas fluorescens, and Rhodobacter sp. based on report in the literature and phylogenetic analysis of seawater intake and fouled RO membrane. The adhesion to RO membrane, the high pressure resistance, and the hydrophobicity of the six model bacteria were examined to find out their fouling potential. Rhodobacter sp. and Mycobacterium sp. were found to attach very well to RO membrane surface compared to others used in this study. The test of hydrophobicity revealed that the bacteria which have high hydrophobicity or similar contact angle with RO membrane ($63^{\circ}$ of contact angle) easily attached to RO membrane surface. P. aeruginosa which is highly hydrophilic ($23.07^{\circ}$ of contact angle) showed the least adhesion characteristic among six model bacteria. After applying a pressure of 800 psi to the sample, Rhodobacter sp. was found to show the highest reduction rate; with 59-73% of the cells removed from the membrane under pressure. P. fluorescens on the other hand analyzed as the most pressure resistant bacteria among six model bacteria. The difference between reduction rates using direct counting and plate counting indicates that the viability of each model bacteria was affected significantly from the high pressure. Most cells subjected to high pressure were unable to form colonies even thought they maintained their structural integrity.

The Present State of Domestic Acceptance of Various International Conventions for the Prevention of Marine Pollution (해양오염방지를 위한 각종 국제협약의 국내 수용 현황)

  • Kim, Kwang-Soo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.12 no.4 s.27
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    • pp.293-300
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    • 2006
  • Domestic laws such as Korea Marine Pollution Prevention Law (KMPPL) which has been mae and amended according to the conclusions and amendments of various international conventions for the prevention a marine pollution such as MARPOL 73/78 were reviewed and compared with the major contents of the relevant international conventions. Alternative measures for legislating new laws or amending existing laws such as KMPPL for the acceptance of major contents of existing international conventions were proposed. Annex VI of MARPOL 73/78 into which the regulations for the prevention of air pollution from ship have been adopted has been recently accepted in KMPPL which should be applied to ships which are the moving sources of air pollution at sea rather tlnn in Korea Air Environment Conservation Law which should be applied to automobiles and industrial installations in land. The major contents of LC 72/95 have been accepted in KMPPL However, a few of substances requiring special care in Annex II of 72LC, a few of items in characteristics and composition for the matter in relation to criteria governing the issue of permits for the dumping of matter at sea in Annex III of 72LC, and a few of items in wastes or other matter that may be considered for dumping in Annex I of 96 Protocol have not been accepted in KMPPL yet. The major contents of OPRC 90 have been accepted in KMPPL. However, oil pollution emergency plans for sea ports and oil handling facilities, and national contingency plan for preparedness and response have not been accepted in KMPPL yet. The waste oil related articles if Basel Convention, which shall regulate and prohibit transboundary movement of hazardous waste, should be accepted in KMPPL in order to prevent the transfer if scrap-purpose tanker ships containing oil/water mixtures and chemicals remained on beard from advanced countries to developing and/or underdeveloped countries. International Convention for the Control if Harmful Anti-Fouling Systems on the Ships should be accepted in KMPPL rather tlnn in Korea Noxious Chemicals Management Law. International Convention for Ship's Ballast Water/Sediment Management should be accepted in KMPPL or by a new law in order to prevent domestic marine ecosystem and costal environment from the invasion of harmful exotic species through the discharge of ship's ballast water.

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