• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.239-243
• /
• 2011

우리나라 주요 수자원인 댐 저수지는 여름철 성층현상으로 인해 많은 수질문제가 발생하여 산기식 수중폭기장치를 설치하고 있다. 그러나 산기식 수중폭기장치의 설계인자들은 대부분 lab-scale의 실험연구를 통해 검토되고 설계에 반영되고 있어 실제 댐 저수지에 적용하기 위해서는 현장적용성을 고려하여 개선될 필요가 있다. 따라서 본 연구는 실제 댐 저수지의 현장조건을 고려하여 CFD 모의실험을 통해 산기식 수중폭기장치의 설계인자인 무차원변수 DN (Destratification Number)과 탈성층 영향반경 및 효율을 검토하였다. 그 결과 현장조건에서의 DN값은 lab-scale 실험조건보다 더 넓은 범위를 가지며, 단위수심당 탈성층 영향반경은 DN값이 증가할수록 감소하는 것으로 분석되었다. 또한 탈성층 효율은 DN값이 증가할수록 선형적으로 증가하다가 증가율이 감소하면서 일정해지는 것으로 분석되었다.

• Environmental engineer
• /
• s.169
• /
• pp.74-78
• /
• 2000

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.5 no.3
• /
• pp.16-22
• /
• 2002

The effect and the overall optimal operation of artificial aeration devices for mixing of thermally stratified water reservoir are under study, and its brief introduction is made. The study site is Yeoncho Lake in Geojae island, which is well known for its eutrophication problems in the summer. A few samplings have been made before and after the operation of two types of artificial aerators, and the effect is believed to be positive. Also, design methodology for such artificial aerators is reviewed and a few are applied to the case of Yeoncho Lake. Schladow's[1993] proposal is believed most proper based on the information we have gathered by now. In addition, a simple numerical experiment is also peformed to see the overall effect of the device on the flow and temperature profile.

• Environmental engineer
• /
• v.25 s.258
• /
• pp.20-23
• /
• 2008

• Environmental engineer
• /
• v.25 s.259
• /
• pp.20-24
• /
• 2008

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.6
• /
• pp.414-420
• /
• 2012

In an effort to commercialization of energy saving aeration apparatus, panel-type aeration membranes were prepared from polyurethane sheet of J company in Korea having tensile strength higher than $400kg_f/cm^2$ with thickness of 0.5mm. Micropores of 100 m size were made by poring technique utilizing needles. From lab-tests in 450 L water tank at temperature of $20^{\circ}C$, the performance of aeration panels at 40 L/min aeration rate showed 5 mg/L DO in less than 3 minutes approaching saturation point of 8 mg/L within 8 minutes. The results show very high efficiency with $K_{La(15)}$ ($16.34hr^{-1}$), Standard oxygen transfer efficiency (SOTE 54.7%) and Standard aeration efficienct (SAE 7.88 kg/kwh). Other pilot scale test in a $2m^3$ water tank with water temperature ($19^{\circ}C$) and aeration rate (30 L/min) showed DO exceeding 5 mg/L within 8 minutes along with $K_{La(15)}$ ($5.8hr^{-1}$), SOTE (42.1%) and SAE (6.41 kg/kwh). These efficiencies represent 2~2.5 times higher than conventional aeration devices. Especially, the achievement of higher Oxygen Transfer Rate indicate higher commercial viability. Conventional aeration devices when applied to clean water and wastewater frequently cause problems due to differences in actual Oxygen Transfer Rate. Our actual tests with $40^{\circ}C$ animal farm wastewater resulted very high efficiencies with Oxygen transfer efficiency ($OTE_f$ 22.1%) and $OTE_{pw40}$ (39.6%).

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.6
• /
• pp.447-452
• /
• 2011

In this study, the polymeric membrane module is used as a diffuser and an image analysis technique based on visual information is applied to get bubble characteristics. The bubble size generated passed through polymeric membrane module was smaller from 30 to 64% than that of air stone, and bubble volume over 70% was ranged from 0.2 to 0.82 mm. But over 80% the bubbles from air stone diffuser ranged from 0.77 to 1.08 mm. The air stone and polymeric membrane module used as diffuser for a flotation system. The floc size inside the flotation reactor using air stone diffuser was bigger than that of the polymeric membrane module, which means that the micro-bubbles generated from polymeric membrane module could provide better opportunities for collisions between colloidal particles than those from air stone diffuser. Therefore, there is a possibility to apply the polymeric membrane module as a diffuser to increase the removal efficiency in the flotation process. Also, the image analysis technique used in this study could be applied as a useful analytical tool for acquisition of an information about the bubble characteristic.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.11
• /
• pp.772-779
• /
• 2012

For improving performance of conical air diffuser generating fine bubble, both experimental and numerical simulation method were used. After adapting diffusers inner real scale bubble column, suitable for various diffuser submergence, the effect of diffuser submergence on oxygen transfer performance such as Oxygen Transfer Coefficient ($K_{L}a_{20}$) and Standard Oxygen Transfer Efficiency (SOTE) was investigated empirically. As flow patterns for various diffuser number and submergence were revealed throughout hydrodynamic simulation for 2-phase fluid flow of air-water, the cause of the change for oxygen transfer performance was cleared up. As results of experimental performance, $K_{L}a_{20}$ was increased slightly by 7% and SOTE was increased drastically by 39~72%, 5.6% per meter. As results of numerical analysis, air volume fraction, air and water velocity in bioreactor were increased with analogous flow tendency by increasing diffuser number. As diffuser submergence increased, air volume fraction, air and water velocity were decreased slightly. Because circulative co-flow is determinant factor for bubble diffusion and rising velocity, excessive circulation intensity can result to worsen oxygen transfer by shortening bubble retention time and amount.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.8
• /
• pp.633-643
• /
• 2015

In this study, we develop a highly efficient conical-air diffuser that generates fine bubble. By inserting a sufficient number of aerotropic microorganisms with dissolved oxygen from an air diffuser and minimizing the air-channel blockages within the air diffuser, we expect to improve the efficiency and durability of the decomposition process for organic waste. To upgrade the conventional air diffuser, we perform experiments and numerical analysis to develop a conical-type that generates fine bubble, and which is free from nozzle blockage. We complement the air-diffuser design by numerically analyzing the internal air-flow pattern within the diffuser. Then, by applying the diffuser to a mockup bioreactor, we experimentally and numerically study the bubble behavior observed in the diffuser and the 2-phase fluid flow in the bioreactor. The results obtained include statistics of the cord length and increased velocity, and we investigate the mechanisms of the fluid-flow characteristics including bubble clouds. Throughout the study, we systemize the design procedures for the design of efficient air diffusers, and we visualize the fluid-flow patterns caused by bubble generation within the mockup bioreactor. These results will provide a meaningful basis for further study as well as the detection of oxygen transfer and fluid-flow characteristics in real-scale bio-reactors using sets of air diffusers.

• JOURNAL OF ELECTRICAL WORLD
• /
• s.254
• /
• pp.53-61
• /
• 1998

오존은, 그 강력한 산화력에 의하여 살균, 탈취, 탈색과 유기물 제거 등의 효과를 복합적으로 얻을 수 있고 또한 신속하게 산소로 분해되어 잔류하지 않기 때문에 환경개선에 사용하기에 이상적인 물질이다. 미쓰비시전기에서는 이러한 오존의 이점에 착안하여 1970년부터 오존발생기와 오존처리설비의 개발, 제품화를 추진하여 왔다. 오존에 의한 고도처리가 널리 일반에게 인정되어 그 수요가 높아지고 있는 오늘날에 있어서도 보다 많은 오존설비의 보급을 위하여 오존기술의 개발에 힘쓰고있다. 본고에서는 상하수도 오존고도처리의 기술동향의 일부로 시도되고 있는 다음의 세 가지 내용을 소개한다. (1)오존처리시스템의 자에너지, 고효율화 기술 방전갭의 단축화, 관분내압력의 고압화로 고농도$\cdot$고효율의 오존발생을 실현하여 자전력화를 가능케 한 신형오조나이저를 개발 제품화하였다. (2)오존 반응조 내에서의 산기장치특성의 파악 모델화가 곤란한 신기장치에 대하여 실설비규모의 실험설비를 사용하여 그 산기특성을 분명히 하였다. (3)과산화수소첨가 오존처리법에 의한 하수처리수의 재생이용 과산화수소첨가 오존처리법에 의하여 장기간에 걸쳐 하수처리수를 전유기탄소(TOC)3mg/$\ell$이하로까지의 처리를 달성하여 하수처리수를 수도수레벨로까지 고도로 정화할 수 있음을 실증하였다.