• Journal of Korean Society of Environmental Engineers
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• v.29 no.2
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• pp.220-228
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• 2007

In this study, effective simultaneous nitrification and denitrification reaction was accomplished in a completely mixed single bioreactor. As the important factors on the reaction, optimal DO concentration and effective range of influent C/N ratio was investigated with the synthetic wastewater. Experimental results show that stable nitrogen removals were accomplished with 0.5 mg/L DO concentration and over 7 C/N ratio. Nitrogen removal efficiency of the real municipal wastewater was low with 0.5 mg/L DO concentration because of its low C/N ratio. The increment of the C/N ratio at the inflow of the municipal wastewater with addition of external carbon source (glucose) over 7(up to 14) shows over 70% nitrogen removal in the single bioreactor.

• Journal of The Korean Society of Clinical Toxicology
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• v.15 no.2
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• pp.122-130
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• 2017

Purpose: To evaluate the effects of low-dose intravenous N-acetylcysteine on the prevention of contrast-induced nephropathy (CIN) in patients undergoing computed tomography (CT). Methods: All patients presenting to our emergency department and undergoing CT with intravenous contrast media between August 2014 and April 2016 were retrospectively enrolled. We included hospitalized patients with renal dysfunction [estimated glomerular filtration rate (GFR) between 30 and $89mL/min/1.73m^2$]. A 600-mg injection of N-acetylcysteine was given to patients once before and once immediately after CT, depending on the preference of physician. The primary outcome was CIN defined as an increase in creatinine level of ${\geq}25%$ or ${\geq}0.5mg/dL$ from the baseline within 48 to 72 hours after CT. A trained person blindly reviewed all medical records. Results: Of the 1903 admitted patients, CIN occurred in 9.8% of patients who received 1200 mg intravenous N-acetylcysteine (24/244) and 6.8% of patients who did not (113/1659, p=0.090). In a multivariable regression analysis, N-acetylcystine was not relevant to the prevention of CIN (odds ratio=1.42 [95% CI, 0.90-2.26]). Even in the stratified analysis using the propensity score matching, N-acetylcysteine was irrelevant (GFR 30-59: odds ratio=1.06 [95% CI, 0.43-2.60]; GFR 60-89: odds ratio=1.76 [95% CI, 0.75-4.14]). After adjustment, crystalloids were significantly associated with the reduction in CIN compared with dextrose water (odds ratio=0.60 [95% CI, 0.37-0.97]). Conclusion: No effect was found when low-dose intravenous N-acetylcysteine was used to prevent CIN. However, there seems to be an association between crystalloids and reduction in CIN.

• Advances in environmental research
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• v.4 no.4
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• pp.263-271
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• 2015

In this study, the effect of initial nitrate loading on nitrate removal and byproduct selectivity was evaluated in a continuous system. Nitrate removal decreased from 100% to 25% with the increase in nitrate loading from 10 to $300mg/L\;NO_3-N$. Ammonium selectivity decreased and nitrite selectivity increased, while nitrogen selectivity showed a peak shape in the same range of nitrate loading. The nitrate removal was enhanced at low catalyst to nitrate ratios and 100% nitrate removal was achieved at catalyst to nitrate ratio of ${\geq}33mg\;catalyst/mg\;NO_3-N$. Maximum nitrogen selectivity (47%) was observed at $66mg\;catalyst/mg\;NO_3-N$, showing that continuous Cu-Pd-NZVI system has a maximum removal capacity of 37 mg $NO_3{^-}-N/g_{catalyst}/h$. The results from this study emphasize that nitrate reduction in a bimetallic catalytic system could be sensitive to changes in optimized regimes.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.538-543
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• 2006

A packed bed reactor (PBR) was fed with nitrate containing synthetic wastewater or effluent from a sequencing batch reactor used for nitrification. The C source introduced into the PBR consisted of volatile fatty acids (VFAs) produced from anaerobic acidogenesis of food wastes. When nitrate loading rates ranged from $0.50\;to\;1.01\;kg\;N/m^{3}{\cdot}d$, the PBR exhibited $100{\sim}98.8%\;NO_{3}^{-}-N$ removal efficiencies and nitrite concentrations in the effluent ranged from $0\;to\;0.6\;NO_{2}^{-}-N\;mg/L$. When the PBR was further investigated to determine nitrate removal activity along the bed height using a nitrate loading rate less than $1.01\;kg\;N/m^{3}{\cdot}d$, 100% nitrate removal efficiency was observed. Approximately 83.2% nitrate removal efficiency was observed in the lower 50% of the packed-bed height. When reactor performance at a C/N ratio of 4 and a C/N ratio of 5 was compared, the PBR showed better removal efficiency (96.5%) of nitrate and less nitrite concentration in the effluent at the C/N ratio of 5. VFAs were found to be a good alternative to methanol as a carbon source for denitrification of a municipal wastewater containing 40 mg-N/L.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.230-237
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• 2006

The operational parameters and control strategies of a tertiary wastewater treatment process a biological filtration system were investigated. The biological filtration system consisted of a nitrification filter (Fiter 1) and a polishing filter with anoxic and aerobic parts (Filter 2). SS, T-C-BOD, and T-N in effluent were kept stable at less than 3, 5 mg/L, and 5 mgN/L, respectively, under a HRT in Filter (filter-bed) of 0.37~2.3 h. T-N at the outlet of Filter 2 were about 1~5 mgN/L under the condition of LV of 50~202 m/d. Methanol addition was controlled based on the COD/N ratio or McCarty's equation. Constant COD/N ratio control results in excess addition under large diurnal fluctuation of $NOx^--N$, and McCarty's equation can be used to add appropriate amount of methanol. Control of methanol addition by on-line nitrate measurement, control of aeration by on-line DO measurement, and control of backwashing by head loss measurement are successfully operated. These results proved that this process prove the easy-maintenance and cost-effectively treatment is attainable.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.3063-3070
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• 2014

In this study, poly(N-methylol methacrylamide) (NMMAAm) and poly(N-methylol methacrylamide/vinyl sulphonic acid) (NMMAAm-VSA) hydrogels were synthesized by $^{60}Co-{\gamma}$ ray irradiation at an ambient temperature. The graphs belonging to the gelation percent- percent-dose and swelling curves were drawn by using data which were obtained from water and different pH solutions. Characterization of hydrogels was performed by FTIR and DSC-TGA analysis. Heavy metal ion ($Ni^{2+}$, $Co^{2+}$) removal capacities of hydrogels were investigated in aqueous solutions, which had different concentrations (100-1500 mg/L). In metal ion removal studies, pH value of aqueous medium was kept constant at 5.0. Maximum metal ion removal values were obtained for NMMAAm-VSA (1:3 mole ratio) hydrogels. Metal ion removal capacities of NMMAAm-VSA (1:3 mole ratio) hydrogels were found as 82 mg/g and 98 mg/g for $Ni^{2+}$ and $Co^{2+}$ ions, respectively.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.3
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• pp.325-334
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• 2012

The objective of this study was to determine the roughage to concentrate (R:C) ratio with rain tree pod meal (RPM) supplementation on in vitro fermentation using gas production technique. The experiment design was a 6${\times}$4 factorial arrangement in a CRD. Factor A was 6 levels of R:C ratio (100:0, 80:20, 60:40, 40:60, 20:80 and 0:100) and factor B was 4 levels of RPM (0, 4, 8 and 12 mg). It was found that gas kinetic, extent rate (c) was linearly increased (p<0.01) with an increasing level of concentrate while cumulative gas production (96 h) was higher in R:C of 40:60. In addition, interaction of R:C ratio and RPM level affected $NH_3-N$ and IVDMD and were highest in R:C of 0:100 with 0, 4 mg of RPM and 40:60 with 8 mg of RPM, respectively. Moreover, interaction of R:C ratio and RPM level significantly increased total volatile fatty acids and propionate concentration whereas lower acetate, acetate to propionate ratios and $CH_4$ production in R:C of 20:80 with 8 mg of RPM. Moreover, the two factors, R:C ratio and RPM level influenced the protozoal population and the percentage of methanogens in the total bacteria population. In addition, the use of real-time PCR found that a high level of concentrate in the diet remarkably decreased three cellulolytic bacteria numbers (F. succinogenes, R. flavefaciens and R. albus). Based on this study, it is suggested that the ratio of R:C at 40:60 and RPM level at 12 mg could improve ruminal fluid fermentation in terms of reducing fermentation losses, thus improving VFA profiles and ruminal ecology.

• Journal of Mushroom
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• v.3 no.2
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• pp.75-78
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• 2005

The results of studies for determining the nutrients sources of mycelial growth for optimal condition of Pleurotus cornucopiae are as follows; 1) Optimal carbon source of mycelial growth of Pleurotus cornucopiae is maltose(357mg/25ml/15d); 2) Optimal nitrogen source of mycelial growth of Pleurotus cornucopiae is peptone(347mg/25ml/15d); 3) Optimal organic acid source of mycelial growth of Pleurotus cornucopiae is glutamic acid(389mg/25ml/15d); 4) Optimal vitamin source of mycelial growth of Pleurotus cornucopiae is biotin(399mg/15d); and 5) Optimal C/N ratio for mycelial growth for determining the condition of Pleurotus cornucopiae is 40(398mg/15d).

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.203-208
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• 2006

A continuous feed and cyclic draw SBR process was developed to overcome flow rate fluctuation and to maximize organic matters utilization efficiency for nitrogen and phosphorus removal. The developed SBR process was operated with two parallel reactors. Influent was supplied to one reactor which was not obligately aerated. At the same time, the other reactor was just aerated without supplying influent. In addition this mode was changed periodically. Cycle time was 6hr and aeration time ratio($t_{aer}/t_{total}$) was 0.33, respectively. $COD_{cr}$ and SS removal efficiencies of 95% or higher were achieved. Nitrogen removal was so greatly influenced by influent $COD_{cr}/T-N$ ratio. At influent $COD_{cr}/T-N$ ratio of 5.7, removal efficiencies of ammonia-N, T-N and T-P were 96%, 78% and 55%, respectively. Influent $COD_{cr}/T-N$ of 4 or higher ratio was necessary to achieve 60% or higher nitrogen removal. Organic matters of influent was efficiently utilized in denitrification reaction and consumed COD has a good correlation with removed T-N(about 6.5 mgCOD/mgTN). Continuous feed and cyclic draw SBR process could be one of alternative processes for the removal of nutrients in rural area where $COD_{cr}/T-N$ ratio was low and fluctuation of flow rate was severe.

• Korean Journal of Environment and Ecology
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• v.28 no.5
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• pp.566-573
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• 2014

Decay rate and nutrient dynamics during leaf litter decomposition of deciduous broad leaf Quercus mongolica and evergreen needle leaf Pinus densiflora were investigated for 69 months from December 2005 to September 2011 in Mt. Worak National Park as a part of National Long-Term Ecological Research Program in Korea. Percent remaining weight of Q. mongolica and P. densiflora leaf litter after 69 months elapsed was $35.4{\pm}2.3%$ and $16.1{\pm}1.3%$, respectively. Decomposition of P. densiflora leaf litter was significantly faster than that of Q. mongolica leaf litter. Decay constant (k) of Q. mongolica and P. densiflora leaf litter after 69 months elapsed was 5.97 and 10.50, respectively. Initial C/N and C/P ratio of Q. mongolica leaf litter was 43.1 and 543.9 respectively. After 69 months elapsed, C/N and C/P ratio of decomposing Q. mongolica leaf litter decreased to 8.7 and 141.2, respectively. Initial C/N and C/P ratio of P. densiflora leaf litter was 151.2 and 391.4, respectively. After 69 months elapsed, C/N and C/P ratio of decomposing P. densiflora leaf litter decreased to 22.9. and 136.5. respectively. Initial concentration of N, P, K, Ca and Mg in leaf litter was 9.30, 0.23, 2.36, 3.14, 1.11 mg/g in Q. mongolica, and 3.02, 0.09, 1.00, 3.84, 0.62 mg/g in P. densiflora, respectively. Initial concentration of N and P in Q. mongolica leaf litter was significantly higher than those in P. densiflora. After 69 months elapsed, remaining N, P, K, Ca and Mg in decomposing leaf litter were 73.8, 60.9, 17.2, 20.3, 35.1 % in Q. mongolica, and 69.5, 75.3, 12.3, 10.9, 10.8 % in P. densiflora, respectively.