• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.27-34
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• 2023

Using ammonia as fuel for solid oxide fuel (SOFC) cells has become an attractive topic nowadays due to its high efficiency, environmental friendliness, and ease of storage and transportation. Several configurations of ammonia-fed SOFC systems have been proposed and investigated, demonstrating high electrical efficiency. However, to further enhance efficiency, it is crucial to understand the inefficient components of the system. The exergy concept is well-suited for this purpose, making exergetic analysis essential for ammonia-fed SOFC systems. This study conducts an exergetic analysis for three selected systems: a simple fuel cell system (FC), an anode off-gas recirculation system (RC-FC), and a recirculation system with water removal (RC-WR-FC). The results reveal that the exergetic efficiencies of the FC, RC-FC, and RC-WR-FC are 48.7%, 51.6%, and 58.4%, respectively. In all three systems, the SOFC stack is the main source of exergy destruction. However, other components with relatively low exergetic efficiency, such as the burner, air heat exchanger, and cooler/condenser, offer greater opportunities for improvement.

• Korean Journal of Microbiology
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• v.39 no.1
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• pp.21-26
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• 2003

Ninety strains of photosynthetic bacteria were isolated from a local stream at Kyonggi-do, Korea and were further screened. Using these isolated strains, experiments were performed under various light and oxygen conditions in order to select strains with high nitrogen $(NH_3-N,\; NO_3^--N)$ removal efficiencies. Results showed that all the strains screened removed $NH_3-N$, the light had no effect on nitrogen removal, and the nitrogen removal rate was higher aerobically than anaerobically. The removal of $NO_3^--N$ was showed up to 35.3% in some specific strains. Results of batch experiments using Rhodocyclus gelatinosus, an isolated strain with a superior removal rate of $NH_3--N$ and $NH_3-N$, under the anaerobic condition, showed that the removal rate of organics and $NH_3-N$ was the highest (98.2 and 89.0%, respectively) at the CODcr (mg/L)/biomass (mg/L) ratio of 0.2, and the $NH_3-N$ concentration did not increase with the decreasing $NH_3-N$ concentration. Experimental results from various C/N ratios confirmed that the effective removal rate (75.8%) of $NH_3-N$ occurred even at the low (5:1) C/N ratio as well as high ratios, and the simulataneous removal of $NO_3^--N$ (96.0%).

• Journal of Wetlands Research
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• v.23 no.1
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• pp.60-66
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• 2021

As the concentration of nitrogen in the sewage flowing into the sewage treatment plant increases due to urbanization and industrialization, the degree of adverse effects such as eutrophication and toxicity to the aquatic ecosystem is also increasing. In order to treat sewage containing high concentration of nitrogen, various studies on the biological nitrogen removal process are being conducted. Existing biological nitrogen removal processes require significant costs for supplying oxygen and supplementing external carbon sources. In this respect, as a high-level nitrogen removal process with economic improvement is required, an anaerobic ammonium oxidation process (ANAMMOX), which is more efficient and economical than the existing nitrification and denitrification processes, has been proposed. The purpose of this study is to confirm the stability of the ANAMMOX process in the water treatment process and to derive the ratio of ammonia nitrogen (NH4+) to nitrite nitrogen (NO2-) for the implementation of the mainstream ANAMMOX process. A laboratory-scale Mainstream ANAMMOX reactor was operated by applying the ratio calculated based on the substrate ratio suggested in the previous study. In the initial range, the removal efficiency of NH4+ was 58~86%, and the average removal efficiency was 70%. In the advanced range, the removal efficiency of NH4+ was 94~99%, and the average removal efficiency was 95%. As a result of the study, as the NH4+/NO2- ratio increased, the stability of the mainstream ANAMMOX process was secured, and it was confirmed that the NH4+ removal efficiency and the total nitrogen (TN) removal efficiency increased. As a result, the results of this study are expected to be used as basic data in the application of the ANAMMOX process in the mainstream.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.745-752
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• 2006

DOS and NaCl aerosol particles were used to determine collection efficiencies of a 2-stage electrostatic wet scrubber with respect to particle size. The DOS and NaCl aerosols have geometric mean diameters of 0.1-3.0 urn, geometric standard deviations of $1.1{\sim}1.8$ and total number concentrations of $450{\sim}2,400\;particles/cm^3$. The tested operating variables for the electrostatic wet scrubber included air velocity and water injection rate. It was shown from the experimental results that particle collection efficiencies increased in the submicron particle size range when different polarities were applied on the water nozzle and corona wire, respectively. This increase in the collection efficiency is attributed to strong electrostatic attraction between the negative water droplets and positive submicron particles. The collection efficiencies also increased when water injection rate was increased or air velocity was decreased. Meanwhile, the pressure drop across the wet scrubber decreased by 90% compared with the existing mechanical wet scrubber. Finally, ammonia gas was used to determine gas removal efficiencies. It was observed that the gas removal efficiencies increased when the air velocity was decreased or the water injection rate was increased.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.730-737
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• 2010

It is very important to remove fluoride ion before treating semiconductor wastewater containing high concentration of ammonia, phosphates, and fluoride ions by struvite formation. Calcium ion was generally added for the removal of fluoride ion. However, calcium ions remained after removal of fluoride ion can deteriorate the performance of struvite crystalization. It should be removed completely before struvite formation. In this study, the effect of fluoride and calcium ion concentration on the struvite crystalization was investigated. Removal efficiencies of ortho-phosphate with struvite formation were more abruptly decreased than those of ammonium nitrogen, as increase of fluoride ion concentration in synthetic wastewater. The structures of struvite formed in synthetic wastewater containing calcium ion of up to 500 mg/L were identical. Purity of struvite was deteriorated as increase of calcium ion over 500 mg/L. Removal efficiencies of ammonium nitrogen were more decreased than those of phosphate ions as increase of cacium ion in synthetic wastewater.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.371-378
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• 2011

Juvenile red seabream (mean body weight 29.0 g) were reared in recirculating culture systems with three different biofilter media, sand (SF), polystyrene microbeads (PF), and Kaldnes beads (KF). The efficiencies of the three different biofilter media were also tested. The SF was fluidized, and the PF and KF were trickled. All treatments were duplicated. The volumetric removal rates of total ammonia nitrogen by SF, PF, and KF were 193.8, 183.9, and 142.6 g $m^{-3}day^{-1}$, respectively, and those of nitrite nitrogen ($NO_2$-N) were 113.4, 105.9, and 85.8 g $m^{-3}day^{-1}$, respectively. The TAN and $NO_2$-N removal rates of KF were lower than those of SF and PF (P < 0.05), but there was no significant difference in these rates between SF and PF (P > 0.05). Among the biofilters used, only KF showed total suspended solid (TSS) removal capacity. The TSS removal efficiencies of SF and PF were negative. The growth rates of fish in SF were significantly higher than those in KF but not higher than those in PF. There was no difference in growth rate between fish in PF and KF. The specific growth rate and feed conversion efficiency of red seabreams in KF were lower than those in SF and PF, but there were no significant differences between SF and PF. These results indicate that sand and polystyrene microbeads are recommended for red seabream culture in a recirculating system.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.2
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• pp.71-78
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• 2013

This study examined the feasibility of phosphorus removal from dewatering centrate/filtrate in wastewater treatment by struvite formation. Since dewatering centrate/filtrate obtained after anaerobic digestion contains a high content of ammonia, magesium addition and pH adjustment could remove phosphorous. The optimum magnesium dose, reaction time, settling time, and pH value was found at 2 mol Mg/mol $PO_4^{3-}$, 10 min, 120 min, and 8.5, respectively. A bench-scale continuous operation at the optimum condition showed 80% of total phosphorus removal and 82% of phosphate removal in dewatering centrate. The elemental composition and crystal structure of the chemical precipitate was similar to the reported values of struvite.

• Asian Journal of Atmospheric Environment
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• v.11 no.1
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• pp.37-53
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• 2017

The effectiveness of four air fresher (AF) systems was evaluated with respect to their removal efficiencies against offensive odorants. For this purpose, malodorous species were generated by exposing freshly cooked foods emitting odorants with levels moderately above their respective threshold values in a confined room. The deodorization efficiency of the four AF systems was then tested for a period of 30 min by estimating the extent of reduction in odorant levels after the operation of each AF. The removal efficiency of the four AF units against each odorant was evaluated as follows: (1) between AF products from different manufacturers, (2) between odorants and ultrafine particulate matter ($PM_{2.5}$), and (3) between operation and natural degassing. The average sorptive removal of odorants was generally <80% and considered less effective or non-effective relative to $PM_{2.5}$. Further examination of odor reduction, if evaluated in terms of odor indices like odor intensity (OI) and odor activity value (OAV), recorded a mean of 33% and 87%, respectively. The overall results of this study confirmed that all tested AF units were not effective to resolve odor problems created under our testing conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.4
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• pp.378-387
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• 2017

This study was performed to isolate bacteria that could control the nitrite levels in a biofloc technology (BFT) culture tank. Nitrite-eliminating bacteria were isolated from a BFT culture tank rearing goldfish, and the isolated bacterium exhibiting the most potent nitrite eliminating ability was labeled as the "NOBSB1" strain. Sequencing the 16S rRNA revealed that NOBSB1 is a species in the genera Bosea. NOBSB1 had the following characteristics with regard to nitrite removal: (1) it removed nitrite by functioning heterotrophically in the presence of a carbon source (sugars); (2) it eliminated nitrite most effectively within a temperature range of $20-30^{\circ}C$, but its activity decreased at temperatures above $35^{\circ}C$ and below $20^{\circ}C$; (3) it had optimum nitrite removal ability within a pH range of 6.0-8.0; (4) it removed nitrite more effectively under hypoxic than aerobic conditions. NOBSB1 inoculation did not decrease ammonia or nitrate levels, but eliminated nitrite in a BFT culture tank rearing common carp (Cyprinus carpio). After inoculating the NOBSB1 strain in a BFT culture tank, NOBSB1 controlled and sufficiently reduced the nitrite concentration in the tank.

• Journal of Korean Society for Quality Management
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• v.43 no.3
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• pp.359-372
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• 2015

Purpose: Through studying the expert's and non-experts panel responses to the questions regarding the attributes of chemical-biological protection cloth quality in terms of the levels of customer demand and technical factors has been studied. We are applied to a QFD matrix with find out the relationship between the selective removal efficiency of chemical-biological cloth and the guidelines of technical approach. Methods: We fabricated several composite of ion-exchange resins with selectively permeable performance designed to facilities water vapor transport and selective adsorption of the harmful gases. With these materials, we characterized on the selectively permeable performance to identify ion-exchange resin with chemical-biological protective cloth. Results: Results showed that ion exchange materials possessed performance with selectively efficiencies as NH3, SOx, NOx and HCl gas. The selective adsorption amount of ammonia and hydrogen gases were $90-80{\mu}g/g$ with TRILITE SCR-BH sulfonated ion exchange resin. The PP non-woven/ion exchange resin adsorbent materials possessed performance with water vapor permeability were 1,100-1,350 g/m2/day, it's was two times high value compare with activated carbon. With these materials, we characterized selectively removal efficiency to identify new ion-exchange material with chemical-biological protective capability. Conclusion: This study shows that a QFD aids in deciding with of the adsorption parameters to optimized with chemical-biological protection cloth manufacturing.