• Particle and aerosol research
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• v.13 no.1
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• pp.17-23
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• 2017

In this study, the test results obtained from the performance tests for CA (Korea Association of Cleaning Air) certificated air cleaners which had been commercially available in Korea from 2003 to 2015 were analyzed. Among the test parameters such as flow rate, particle collection efficiency, clean air delivery rate (CADR), ozone emission, odor removal efficiency and noise level, noise level and CADR were correlated with flow rates. Collection and odor removal efficiencies were 20% higher than the limit of the CA certification. The ozone emissions from the air cleaners were negligible because all the air cleaners were equipped with only HEPA filters, not electrostatic precipitation method which produces ozone.

• Journal of environmental and Sanitary engineering
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• v.12 no.3
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• pp.73-79
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• 1997

This research was intended as an investigation of applying Reduced Pressure Evaporation as efficient treatment method for landfill leachate. According to the variance of time, temperature, pressure and pH in experiments, the properties of leachate treatment are follows. The removal efficiencies of COD, NH$_{3}$-N, TOC, Conductivity and SS on the basis of reaction time was 96.4%-97.5%, -1.4%-53.7%, 81.7%-89.0%, 92.0%-95.3% and 99.86%-99.97%, respectively. When the pH of Influent was 7.5, the pH of effluent was increased to 10-11 with time elapse. It is concluded that the orgin of pH increase may be ammonia. When the properties of concentrate were investigated at the concentration ratio 90%(V/V), concentration difficiency represented in the ratio of experimental value/calculated value had following orders ; COD>TOC>NH$_{3}$-N>Conductivity>SS. Concentrate had good precipitation because of additive thermal treatment in the process. When evaporation experiments with pH adjustment of 4.0, 6.0, 7.5, 9.0 and 10.0 were performed ; Acidic evaporation experiments(pH 4.0, 6.0) showed low removal efficiency(81.6, 87.6%) of COD and high removal efficiency (97.5%. 84.6%) of NH$_{3}$-N at initial evaporation. Basic evaporation(pH 9.0, 10.0) showed high removal efficiency (97.2%, 98.9%) of COD and very low removal efficiency (-7.4%, -27.2%) of NH$_{3}$-N at initial evaporation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.262-269
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• 2016

This study examined the influent of a sulfur denitrification reactor using nitrified effluent from a batch type reactor. The denitrification efficiency was compared according to the injection type. The nitrogen removal effects were compared with the changes in the EBCT and nitrogen concentration of the influent to determine the optimal operation conditions with the selected injection type. A denitrification efficiency evaluation of a reactor according to the change in injection type and up-flow was performed using a lower organic concentration of the effluent than the down-flow because of the re-precipitation of desorbed microbes and spilled solids. In the up-flow type, organics were controlled by the low concentration than the down-flow type because of solid re-precipitation. The T-N removal efficiency of the up-flow type was 73.3~90.2%, which was more that 10% higher that down-flow type. This means that the up-flow type has a great advantage in removing T-N and organics. The T-N removal efficiency by EBCT at 1hr was 47.3%, and was 88.1% and 90.5% by EBCT 3hr and 5hr, respectively. Therefore, the optimal operation conditions to remove nitrogen was considered to be EBCT for 3hr. After careful consideration of rule of law and T-N removal effects, the T-N load factor in the reactor should remain below $0.443kgT-N/m^3{\cdot}day$ to maintain the legal total nitrogen concentration for discharge, which is 20mg/L.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.78-84
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• 2015

The purpose of this study is to evaluate the removal efficiency of phosphorus from synthetic waste water by reduction and oxidation reaction of Cu-Zn metal alloy. Cu-Zn metal alloy applied in this study is composed of 40% of Zn and 60% of Cu, which is so called Muntz metal. And the fibrous type of metal alloy has approximately $200{\mu}m$ of thickness. Metal is oxidized in an aqueous solution to generate electron and metal ion. The mechanism of phosphate treatment is co-precipitation of metal ion and phosphorous ion at various pH and temperature. The treatment efficiency showed the maximum at a one cycle treatment. This result means that the surface area of reaction material is sufficient enough to get reaction equilibrium. Experiment is conducted at various pH from 5 to 9, and showed the maximum efficiency at pH 8. Phosphorous is dominated as a type of $H_2PO_4{^-}$ and $HPO_4{^{2-}}$ at this pH condition. We could not consider the temperature effect independently, because phosphorous removal efficiency showed such a complex mechanism. We could get high efficiency at lower temperature in this research.

• Journal of Soil and Groundwater Environment
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• v.8 no.1
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• pp.17-26
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• 2003

The sorption experiment of cobalt was performed after the TRIGA soil was intentionally contaminated with cobalt was found that the sorption equilibrium coeficiency of soil decontamination was high when the ratio of soil mass to the volume of citric acid becomes 1:5 The TRIGA soil contaminated with 0.01 M, 0.001 M, and 0.0001 M of cobalt solution were decontaiminated with 0.01 M citric acid. The cobalt concentrtion in the wastewater were measured to be correspondingly 36.0, 14.0, 1.5 ppm. The results of wastewater recycling experiment by chemical precipitation method revealed that corresponding cobalt removal efficiency were 97% 88%. It was shown that the removal efficiency decreases as the cobalt concentration in the wastewater decreases. During the decontamination experiment, a lot of NaOH had to be added, and the volume of final solid waste reached almost 10% of that of the contaminated soil. The result of wastewater recyling experiment by ion exchange resin meted rethod revealed that to more the strong acid resins are used, the higher the cobalt removal efficiency becomes and the cobalt removal efficiency becomes and the lower the pH of recycling wastewater become. In order to obtain more than 95% removal efficiency, more than 0.625 g of strong acid resin was necessary in each of 3 experiments. There was an unexpected problem that a lot of strong acid resin waste was produced which amounts to 9.2% (volume) of the contaminated soil.

• Journal of agriculture & life science
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• v.45 no.3
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• pp.89-96
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• 2011

The objective of this study is to evaluate reduction efficiency of various air purifiers on airborne microorganism causing air infected animal disease according to sample collection method. Collection efficiencies of MS2 virus and Pseudomonas fluorescens by biosampler was significantly higher than those by button sampler (p<0.05). Regardless of types of air purifier and sample collection method, temporal reduction efficiencies of MS2 virus and P. fluorescens compared to initial background concentration were >50% and >45% on 5 minutes, >70% and >50% on 15 minutes, >80% and >70% on 30 minutes and >90% and >75% on 60 minutes after operating air purifier, respectively. The air purifier of ionizer type showed the highest reduction efficiency on MS2 virus followed by air purifier of electronic precipitation, water filter and dry filter while the reduction efficiency of air purifier on P. fluorescens was highest in the electronic precipitation type followed by ionizer type, dry filter type and water filter type (p<0.05). Based on the results obtained from this study, temporal reduction efficiency of air purifier on MS2 virus was relatively higher than P. fluorescens.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.679-682
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• 2004

$SrGa_2S_4$:Eu green phosphor and SrS:Eu red phosphor have been synthesized by co-precipitation method, respectively. Two sulfide phosphors were influenced by oxygen defect in host materials. Excitation spectra of these phosphors have high efficiency at the long wavelength region. And emission efficiency is increased under the excitation wavelength of 465nm. The combination of thiogallate green phosphor and sulfide red phosphor based on blue light InGaN chip has made it possible to emit white light.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.240-244
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• 1998

This study was carried out to investigate the efficiency of steel mill slag and sludge in removing heavy metals and cyanide in metal plating wastewater. Laboratory experiments were peformed with jar tester, The tests were peformed at ambient temperature. The results of tests showed that overall rates metals removed were greater than 90 %. Metals were removed from solution as the combined effects of adsorption and precipitation in alkaline condition. The removal efficiency of cyanide by steel mill wastes was above 90 % at optimum conditions. In view of the test results and other engineering characteristics of steel mill slag and sludge, these industrial by-products from steel industry have a high potential to be used in metal plating wastewater treament and were particularly beneficial.

• Journal of the Korea Organic Resources Recycling Association
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• v.10 no.1
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• pp.102-108
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• 2002

The effects of ammonia on mesophilic anaerobic digestion were investigated by operating lab-scale two-stage ASBF reactors using swine wastewaters as influent without and with ammonia removal at HRT of 1-2 days and OLR of $2.2{\sim}9.6kg-COD/m^3{\cdot}d$ for 250 days. The COD removal efficiency and biogas generation of two-stage ASBF reactors was decreased by increasing influent ammonia concentrations to 1,580 mg(T-N)/L with increasing OLR to $6.3kg-COD/m^3{\cdot}d$, while those were increased by maintaining influent ammonia concentrations below 340 mg(T-N)/L by MAP precipitation with increasing OLR to $9.6kg-COD/m^3{\cdot}d$. Initial inhibirion of ammonia on anaerobic processes was observed at a concentration of 760 mg(T-N)/L and the COD removal efficiency and biogas generation dropped to 1/2 at ammonia concentration ranges of 1,540~1,870 mg(T-N)/L. It is essential to remove ammonia in swine wastewaters to an initial inhibition level before anaerobic processes for the effective removal of COD.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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• pp.140-144
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• 2000

In treatment of contaminated ground by electrokinetic remediation, pH control is the main prolllem for enhancinfi remediation efficiency. In this study, analysed pH variation characteristics according to contaminant(Pb$^{2+}$) concentration and estimated remediation efficiency with organic acid to prevent precipitation in cathode due to hydroxide ion occurrence. Because most of transported Pb$^{2+}$ is precipitatecl according as pH is increased at specimen adjacent to cathode reservoir, little magnitude of Pb$^{2+}$ is flowed out of specimen.cimen.