• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.190-190
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• 2011

본 논문에서는 자외선 처리방식의 선박평형수 처리시스템의 최적 설계를 위하여 동일 소비전력에서 살균 챔버의 구성에 따른 해수처리성능에 대하여 기술하였다. 20 W 저압 자외선 램프 9개를 설치한 살균챔버와 10 W 저압 자외선 램프를 18개 사용한 2단 구성의 살균챔버를 사용하여, 15 $m^3$/h로 해수를 처리하고 처리 전후의 해수내 미생물에 대한 처리성능을 비교.분석하였다.

• Journal of Marine Life Science
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• v.4 no.2
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• pp.86-90
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• 2019

This study aimed to compare the disinfection efficiencies of the ultraviolet and plasma systems, the two systems designed and commercialized to disinfect water in aquaculture, by putting each in a 100 ℓ water tank and concentrating 1.0 ℓ of treated water to check the changes in the number of bacteria in the samples. Each system was operated for 6 hours to culture the typical seawater bacteria in the Marine agar, Thiosulfate citrate bile salts sucrose agar and Salmonella Shigella agar media, respectively, to check the number of bacteria in the media, and the changes in the number of Edwardsiella piscicida in the treated water were checked after the artificial inoculation of E. piscicida in the disinfected seawater. As a result, the two disinfection systems showed the almost similar levels of bacterial reduction efficiency between 99.5% and 99.9%. However, the result of this study showed that, with 100 ℓ of water treated for the same length of time using the two systems, the plasma system turned out to disinfect bacteria in a shorter period of time than the UV system. However, as the changes in the number of bacteria were checked for a short length of time (6 hours) in this study, it was judged that, considering the actual aquaculture environment in which the quality of water significantly changes with feed residues, excretions and coastal contamination, etc., and a lot of biofilms and organic matter exist, the plasma system would be more efficient than the UV system as the former is capable of continuously maintaining a certain level of efficiency than the latter that is limited in terms of efficiency depending on the level of turbidity and the existence of organic matter.

• Journal of Korean Society on Water Environment
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• v.26 no.6
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• pp.1028-1033
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• 2010

Wastewater reuse for agricultural irrigation needs treatment and control of pathogens to minimize risks to human health and the environment. In order to evaluate the water quality of UV-treated reclaimed water, this study focused on the relationship between micro-pathogens and particulate matters. MS2 was selected as an index organism because it has similar characteristics to human enteric virus and strong resistance to UV disinfection. The turbidity and suspended solid (SS) were selected for test parameters. In this study, it was performed with different UV doses (30 and $60mJ/cm^2$) for estimation of the MS2 inactivation rate using collimated beam batch experiments in the laboratory. The experiment results by turbidity or SS concentration presented that the increased concentration of them lowered MS2 inactivation. At the turbidity (below 4.27 NTU) and SS (below 1.47 mg/L) of the low level range, the inactivation of 60 UV dose is higher than 30 UV dose. However, at the turbidity and SS of the high level, the increasing UV dose did not show apparent increasing the MS2 inactivation. In quantitative microbial risk assessment (QMRA), it can confirm the trend that $P_D$ and turbidity concentrations have positive correlationship at the low concentration, which was also observed in SS. The QMRA can be helpful in communication with public for safe wastewater reuse and be recommended.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.1
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• pp.55-65
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• 2018

It is necessary to develop a mobile water production system in order to provide stable water supply in case of disasters such as floods or earthquakes. In this study, we developed a modular mobile water production system capable of producing water for various uses such as domestic water and drinking water while improving applicability in various raw water sources. The water production system consists of three stages of filtration (sand filtration - activated carbon filtration - pressure filtration) to produce domestic water and an additional reverse osmosis process to produce drinking water. In laboratory and field experiments, the domestic water production system showed excellent treatment efficiency for particulate matter, but showed limitations in the treatment of dissolved substances such as dissolved organic matter. In addition, ultraviolet irradiation was considered as additional disinfection step, because it does not form precipitates of manganese oxides after disinfection. Reverse osmosis process was added to increase the removal efficiency of dissolved substances and the treated water satisfied drinking water quality standards. Fluorescence analysis of dissolved organic matter showed that the fulvic acid-like substances in raw water was successfully removed in the reverse osmosis process. The mobile water production system developed in this study is expected to be used not only in water supply in case of disaster, but also widely used in islands and rural area.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.226-237
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• 2020

As the number of reported COVID-19 cases rises around the world, regions affected by the virus are taking serious measures to contain its spread. Face shields are one of the highest-need personal protective equipment (PPE) during COVID-19 pandemic. Beyond traditional face masks, as known cases of the coronavirus soar, currently there is a significant shortage of face shields around the world. In response, the protective face shields were designed and fabricated with open-source 3D modelling software and 3D printing technology, respectively. Our face shield consisted of two parts only; a reusable 3D printed headband and a visor made of transparent plastic sheet, as barrier. The resulting 3D printed face shields are affordable, lightweight, one-size-fits-most and ready-to-wear with minimal assemblies, and go on easily over glass, goggle and face mask. To ensure being donated to the healthcare professionals without risk infected by any pathogens, the 3D printed face shields were successfully be disinfected with ultraviolet germicidal irradiation (UVGI dosage of 1000 mJ/cm²) and 70% alcohol. For routine disinfection a UVGI chamber was designed and optimized to provide uniform UV-C illumination with an appreciated fluence for complete decontamination. More than 1,000 face shields were produced already and donated to the special hospitals for COVID-19 patients, quarantines, government and medical agencies in Ethiopia as well as in East-African countries. With certainty, our intention goes beyond the hospitals and other first responders, but not limited for all those who have to stay in the service or be in contact with many other people in the time of COVID-19 pandemic.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.769-775
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• 2013

UV-induced transformations in the characteristics of dissolved organic matter (DOM) and the subsequent effects on the disinfection by-product formation potential (DBPFP) were investigated using the mixtures of the two humic substances with different sources, and two different size fractions of Suwannee River fulvic acid (SRFA). 7 day-photodegradation resulted in the decrease of specific ultraviolet absorbance (SUVA) of the mixtures as well as the specific DBPFP. After the irradiation, however, higher specific DBPFP values were consistently observed at the same range of the SUVA values. This suggests that non UV-absorbing components, generated by the UV-irradiation, may contribute to the formation of DBPs. Two different molecular size fractions of SRFA showed dissimilar responses to photodegradation. The behavior was also influenced by the types of the DBPs generated. Higher levels of trihalomethenes (THMs) were formed per organic carbon for the high molecular fraction compared to the low molecular fraction, whereas no differences were found in the formation of haloacetic acids (HAAs) between the two different size fractions. The formation of the two types of DBPs also differed by the irradiation times. Specific formation potential of THMs consistently increased upon the irradiation, whereas HAAs showed the initial increase followed by the decrease in their specific formation potential.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1204-1210
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• 2014

New control methods are proposed for indoor air quality by removing fine airborne dust-particles. As suspended fine dust-particles contain inorganic dust as well as fine organic bacteria, studies for simultaneous control of these contaminants are required. In this study, photocatalytic disinfection of indoor suspended microorganisms such as E. coli and Bacillus subtilis is performed by three types of photocatalysts with UVA irradiation. The UVA irradiation strength was controlled to the minimum $3{\mu}W/cm^2$, and ZnO, $TiO_2$, and ZnO/Laponite ball were used as the catalysts. The results indicate that E. coli was removed over 80 % after about 2 hours of reaction with UVA and all three types of photocatalysts, whereas only with UVA, around 50 % E. coli removal was obtained. Among the catalysts, ZnO/Laponite composite ball was found to have similar sterilizing capacity to $TiO_2$. However, in case of B. subtilis, which has thick cell wall in its spore state, disinfection was not effective under the low UVA irradiation condition, even with the catalysts. Further studies need to figure out the optimal UVA irradiation ranges as well as photocatalysts doses to control airborne dust, to provide healthy clean air environment.

• Environmental Engineering Research
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• v.12 no.5
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• pp.224-230
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• 2007

The objectives of this study were to evaluate the change of molecular weight (MW) profiles in natural organic matter (NOM) through various treatment processes (coagulation, granular activated carbon (GAC), and ozonation) using high performance size exclusion chromatography based on ultraviolet absorbance and dissolved organic detection (HPSEC-UVA-DOC). In addition, relationships between MW profiles and disinfection by-production (DBP) formation were evaluated. Each treatment process results in significant different effects on NOM profiles. Coagulation is effective to remove high molecular weight NOM, while GAC is effective to remove low molecular weight NOM. Ozonation removes only a small portion of NOM, while it induces a significant reduction of UV absorbance due to breakdown of the aromatic groups. All treated waters are chlorinated, and chlorination DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) are measured under formation potential conditions. Both THM and HAA formation potentials were significantly reduced through the coagulation process. GAC was more effective to reduce THM formation compared to HAA formation reduction, while ozonation showed significant HAA reduction compared to THM reduction.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.95-100
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• 2009

The water purification systems have been hardly used for agricultural purpose due to their complicated compositions and high costs for farmers, while only simple filtrations have been applied to irrigation systems in order to prevent the system from clogging problems. This study therefore developed a clean water supplying system, the Filter-Disinfection-Adsorption (FDA) system, especially for greenhouse cultivation of where low quality of water is available. This system has also been produced for providing convenience water to farmers in the areas of no water supply service systems for the purpose of washing their bodies or agricultural machineries after farm work. The FDA system consists of three stages of purification processes with an integral module, including disk and teflon filtrations and Ultraviolet (UV) sterilization processes. Indoor experiments were undertaken with a trial product of the FDA system to test its performance. The operation test of the process was performed as well as the condition check of each item including UV module, filters, control panel, pump, valves, etc. The results shows good performance of each test with no critical problems. The initial and maintenance costs were also analysed with other purification systems. From the comparisons, the FDA system found to be very economical and easy to use.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.4
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• pp.521-533
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• 2012

Interest in application of ultraviolet light technology for primary disinfection that used for the treatment of water for consumption and wastewater has increased significantly in recent years. Analysis of these systems has been carried out using Computational Fluid Dynamics (CFD) procedure. It offers advantages over other techniques in specific circumstances. CFD has emerged as a powerful tool to aid design of a UV reactor by providing the UV dose delivered by the proposed reactor design and allowing engineers to evaluate alternative designs in much less time and at a reasonable cost. In this study, five different configurations of the apparatus depending on the location of the exit are evaluated in terms of maximum dose, minimum dose, flow patterns, particle tracks and transient dose. The configuration 3 results have higher minimum UV dose value and uniform particle distribution of the UV dose on the outlet than other's.