• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.951-956
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• 2005

Selection of oxygen-tolerant strains and elucidation of their oxygen tolerance mechanism were crucial for effective use of bifidobacteria. Oxygen-tolerant bifidobacteria were able to significantly remove environmental oxygen (oxygen removal activity) as compared to oxygen-sensitive strains. Most oxygen removal activity was inhibited by heat treatment and exposure to extreme pH (2.0) of bifidobacterial cell. NADH oxidase was major enzyme related to oxygen removal activity. Oxygen-tolerant bifidobacteria possessed high NADH peroxidase activity level to detoxify $H_2O_2$ formed from reaction of NADH oxidase. Addition of oxygen to anaerobic culture broth significantly increased activities of HADH oxidase and NADH peroxidase within 1hr and rapid increment of oxygen concentration was prevented. Results showed NADH oxidase and NADH peroxidase of oxygen-tolerant bifidobacteria played important roles in elimination of oxygen and oxygen metabolite $(H_2O_2)$.

• Journal of Microbiology and Biotechnology
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• v.27 no.10
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• pp.1798-1807
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• 2017

The differentiations in nitrogen-converting activity and microbial community structure between granular size fractions in a continuous completely autotrophic nitrogen removal over nitrite (CANON) reactor, having a superior specific nitrogen removal rate of $0.24g/(g\;VSS{\cdot}h)$, were investigated by batch tests and high-throughput pyrosequencing analysis, respectively. Results revealed that a high dissolved oxygen concentration (>1.8 mg/l) could result in efficient nitrite accumulation with small granules (0.2-0.6 mm in diameter), because aerobic ammonium-oxidizing bacteria (genus Nitrosomonas) predominated therein. Meanwhile, intermediate size granules (1.4-2.0 mm in diameter) showed the highest nitrogen removal activity of $40.4mg/(g\;VSS{\cdot}h)$ under sufficient oxygen supply, corresponding to the relative abundance ratio of aerobic to anaerobic ammonium-oxidizing bacteria (genus Candidatus Kuenenia) of 5.7. Additionally, a dual substrate competition for oxygen and nitrite would be considered as the main mechanism for repression of nitrite-oxidizing bacteria, and the few Nitrospira spp. did not remarkably affect the overall performance of the reactor. Because all the granular size fractions could accomplish the CANON process independently under oxygen limiting conditions, maintaining a diversity of granular size would facilitate the stability of the suspended growth CANON system.

• Journal of Environmental Science International
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• v.28 no.7
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• pp.629-637
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• 2019

The purpose of this study was to evaluate the effect of high-salinity wastewater on the microbial activity of Aerobic Granule Sludge (AGS). Laboratory-scale experiments were performed using a sequencing batch reactor, and the Chemical Oxygen Demand (COD), nitrogen removal efficiency, sludge precipitability, and microbial activity were evaluated under various salinity injection. The COD removal efficiency was found to decrease gradually to 3.0% salinity injection, and it tended to recover slightly from 4.0%. The specific nitrification rate was 0.043 - 0.139 mg $NH_4{^+}-N/mg$ $MLVSS{\cdot}day$. The specific denitrification rate was 0.069 - 0.108 mg $NO_3{^-}-N/mg$ $MLVSS{\cdot}day$. The sludge volume index ($SVI_{30}$) ultimately decreased to 46 mL/g. The specific oxygen uptake rate decreased from an initial value 120.3 to a final value 70.7 mg $O_2/g$ $MLVSS{\cdot}hr$. Therefore, salinity injection affects the activity of AGS, causing degradation of the COD and nitrogen removal efficiency. It can be used as an indicator to objectively determine the effect of salinity on microbial activity.

• Journal of Korean Society on Water Environment
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• v.27 no.2
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• pp.188-193
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• 2011

The effects of coagulants on the microorganisms when they are injected directly into the biological treatment facility for T-P removal have been easily observed from the results of past experiments. As such this study is set out to derive the effective plans for the coagulant dosage by analyzing the effects of the injected coagulant on the microbial activity during the chemical treatment for T-P removal. The research methods entailed the assessment of removal efficiency of T-P according to the coagulant dosage while changing the molar ration between Alum and influent phosphorus. At the same time Specific Oxygen Uptake Rate (SOUR) according to the coagulant dosage was measured. SOUR was used as a method for indirect assessment of the microbial activity according to the coagulant dosage. The results from the study showed that with the increase in the alum dosage, the removal efficiency T-P tended to increase. On the other hand, the increase in coagulant dosage resulted in the decrease in SOUR, which indicates the decrease in the microbial activity. Such reduction in the activity could be explained by the increase in the concentration of removal efficiency of $TBOD_5$. Based on experiment results from the study, it is determined that coagulant dosage affects the microbial activity. Moreover, the indirect assessment on the microbial activity using SOUR is considered possible.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.E2
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• pp.41-48
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• 2005

A novel hybrid system composed of a biotrickling filter and an activated sludge reactor was investigated under the conditions of four different SRTs (sludge retention times). The performance of the hybrid reactor was found to be directly comparable among the four different sludge ages. Discernible differences in the removal performance were observed among four different SRTs of 2, 4, 6, and 8 days. High removal efficiency was achieved by continuous circulation of activated sludge over the immobilized mixture culture, which allowed on pH control, addition of nutrients, and removal of paint VOCs (volatile organic compounds). The results also showed that the removal efficiency for a given pollutant depends on the activity of microorganisms based on the SRT. As the SRT increased gradually from 2 to 8 days, the average removal performance decreased. The highest removal rate was achieved at the SRT of 2 days at which the highest OUR (oxygen uptake rate), $6.1mg-O_2/liter-min$ was measured. Biological activity in the recycle microbes decreased to a much lower level, $3.6mg-O_2/liter-min$ at a SRT of 8 days. It is thus believed that young microorganisms were more active and more efficient for the VOCs removal of low concentrations and high flow rates. The apparent correlation of $R^2=0.996$ between the average removal efficiency and the average OUR at each SRTs suggests that VOCs degradation by young cells significantly affected the overall removal efficiency for the tested SRTs.

• Nuclear Engineering and Technology
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• v.28 no.5
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• pp.482-487
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• 1996

The dissolved oxygen removal by H$_2$-O$_2$ reaction in column packed with various catalysts wes examined. The catalysts employed were the prepared polymeric catalyst platinum on activated carbon, and Lewatit OC-1045 which is available commercially. The column experiments with the prepared polymeric catalyst showed the dissolved oxygen reduced to 35 ppb which is below the limit in feed water of power plants. This implies the likely application of the prepared catalyst for practical use. The activated carbon required the pre-treatment for the removal of dissolved oxygen, since the surface of activated carbon contains much oxygen adsorbed initially. The Lewatit catalyst exposed the best performance, however, the aged one showed the gradual loss of catalytic activity due to degradation of resin catalyst.

• Journal of Korean Society on Water Environment
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• v.38 no.4
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• pp.171-176
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• 2022

Recently, an autotrophic single-stage nitrogen removal (ASSNR) process based on the anaerobic ammonium oxidation (ANAMMOX) reaction has been proven as an economical ammonia treatment. It is highly evident that double-layered gel beads are a promising alternative to the natural biofilm for ASSNR because of the high mechanical strength of poly(vinyl alcohol) (PVA)/alginate structure and efficient protection of ANAMMOX bacteria from dissolved oxygen (DO) due to the thick outer layer. However, the thick outer layer results in severe mass transport limitation and consequent lowered bacterial activity. Therefore, the effects of the thickness of the outer layer on the overall reaction rate were tested in the biofilm model using AQUASIM for ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB) and ANAMMOX bacteria. A thickness of 0.5~1.0 mm is preferred for the maximum total nitrogen (TN) removal. In addition, a DO of 0.5 mg/L resulted in the best total nitrogen removal. A higher DO induces NOB activity and consequent lower TN removal efficiency. The optimal density of AO B and NO B density was 1~10% for a 10% ANAMMOX bacterial in the double-layered PVA/alginate gel beads. The real effects of operating parameters of the thickness of the outer layer, DO and concentrations of biomass balance should be intensively investigated in the controlled experiments in batch and continuous modes.

• Environmental Engineering Research
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• v.24 no.3
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• pp.376-381
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• 2019

In this study, a poly(vinyl) alcohol/sodium alginate (PVA/SA) mixture was used to fabricate core-shell structured gel beads for autotrophic single-stage nitrogen removal (ASNR) using aerobic and anaerobic ammonia-oxidizing bacteria (AAOB and AnAOB, respectively). For stable ASNR process, the mechanical strength and oxygen penetration depth of the shell layer entrapping the AAOB are critical properties. The shell layer was constructed by an interfacial gelling reaction yielding thickness in the range of 2.01-3.63 mm, and a high PVA concentration of 12.5% resulted in the best mechanical strength of the shell layer. It was found that oxygen penetrated the shell layer at different depths depending on the PVA concentration, oxygen concentration in the bulk phase, and free ammonia concentration. The oxygen penetration depth was around $1,000{\mu}m$ when 8.0 mg/L dissolved oxygen was supplied from the bulk phase. This study reveals that the shell layer effectively protects the AnAOB from oxygen inhibition under the aerobic conditions because of the respiratory activity of the AAOB.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.135-142
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• 2021

The activity of anaerobic ammonium oxidation (ANAMMOX) immobilized in synthetic media (Poly Ethylene Glycol, PEG) and granular form was evaluated comparatively to investigate the effect of influent nitrogen concentration and exposure of oxygen. In ANAMMOX granule reactor, when concentration of influent total nitrogen increased to 500mg/L, removal efficiency of ammonium, nitrite and nitrate were shown to 90.5±6.5, 96.6±4.9, and 93.2±6.1%, respectively. In the case of the PEG gel, it showed lower nitrogen removal performance, resulting in that the removal efficiency of ammonium, nitrite and nitrate were shown to 83.3±13.0, 96.4±6.1, and 90.3±7.5%, respectively. In second step, when exposed to oxygen, the nitrogen removal performance in the ANAMMOX granule reactor also remained stable, but the activity of PEG gel ANAMMOX was found to be inhibited. Consequently, the PEG gel ANAMMOX was a higher sensitivity than that of granular ANAMMOX with two variables applied in this study.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.577-585
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• 2014

A series of experiments using atmospheric-pressure non-thermal plasma coupled with transition metal catalysts were performed to remove ethylene from agricultural storage facilities. The non-thermal plasma was created by dielectric barrier discharge, which was in direct contact with the catalyst pellets. The transition metals such as Ag and $V_2O_5$ were supported on ${\gamma}-Al_2O_3$. The effect of catalyst type, specific input energy (SIE) and oxygen content on the removal of ethylene was examined to understand the behavior of the hybrid plasma-catalytic reactor system. With the other parameters kept constant, the plasma-catalytic activity for the removal of ethylene was in order of $V_2O_5/{\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ from high to low. Interestingly, the rate of plasma-catalytic ozone generation was in order of $V_2O_5/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$, implying that the catalyst activation mechanisms by plasma are different for different catalysts. The results obtained by varying the oxygen content indicated that nitrogen-derived reactive species dominated the removal of ethylene under oxygen-lean condition, while ozone and oxygen atoms were mainly involved in the removal under oxygen-rich condition. When the plasma was coupled with $V_2O_5/{\gamma}-Al_2O_3$, nearly complete removal of ethylene was achieved at oxygen contents higher than 5% by volume (inlet ethylene: 250 ppm; gas flow rate: $1.0Lmin^{-1}$; SIE: ${\sim}355JL^{-1}$).