• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.65-71
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• 2010

This study was conducted to investigate the dynamics of nutrients such as total nitrogen (TN), nitrate nitrogen ($NO_3$-N) total phosphorous (TP), and phosphate phosphorous ($PO_4$-P) in outflow from a cabbage farmland in a mixed land-use watershed. The TN concentrations in groundwater showed twice peaks in late July 2006 and late March 2007 (3.8, 4.7 mg/L, respectively), when it rained shortly after fertilizer application, indicating that nitrogen leaching is greatly influenced by fertilization and rainfall. The mean concentrations of TN and $NO_3$-N in surface water were not significantly higher than those in groundwater, while the mean concentrations of TP and $PO_4$-P in surface water were significantly (p < 0.05) were higher than those in groundwater. The TN concentrations in groundwater were generally higher than those in surface water during fertilization and early growing season due to the effect of fertilization, but vice versa in the other periods. In contrast, the TP concentrations in groundwater were always lower than those in surface water due to the sorption of particulate phosphorous by soil. The ratio of TN load in baseflow to that in total TN load (39 %) was much greater than the TP ratio (7 %), suggesting that baseflow contribute to nitrogen export. Therefore, proper fertilization management should be taken to reduce nitrogen load through baseflow.

• KSBB Journal
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• v.7 no.2
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• pp.102-106
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• 1992

Effects of nitrogen souses and C/N ratio were investigated on the production of extracellular microbial surfaclant, sophorolipid, from C. bombiocola. Organic nitrogen sources, such as urea, peptone and yeast extract was found to be more effective for sophorolipid production, than inorganic nitrogen sources. Depending on the nitrogen sources, sophorolipid production pattern varied by increasing C/N ratio. Increased production of sophrolipid could be obtained up to 90g/L by feeding carbon source again 2 days after cultivation.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.46-51
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• 2002

This study was performed to treat a sewage at the upper stream of dam using modified sequencing batch reactor, During the operating period, average $COD_{cr}$, removal efficiency was about 85% but average T-N and ${PO_4}^{3-}-P$ removal efficiencies were 43% and 30% respectively. Because the organic matter was very low compared with nitrogen and phosphorous in influent($BOD_{5}/{NH_4}^{+}-N{\;}={\;}2,{\;}BOD_{5}/{PO_4}^{3-}-P{\;}={\;}15.6$), nitrogen and phosphorus removal efficiency was relatively low. Average nitrogen removal efficiency was 50 % at $10^{\circ}C$ or above and it was 36 % at $10^{\circ}C$ or below. As reactor was located in outdoor without any thermostat, temperature decreased at least $2.4^{\circ}C$ in the winter season. Therefore, if we would apply this modified sequencing batch reactor to sewage which concentration of organic matter was very low compared with nitrogen and phosphorous, we have to addition of external carbon and installation of any thermostat.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.6
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• pp.896-902
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• 2015

Milking center wastewater (MCW) has a relatively low ratio of carbon to nitrogen (C/N ratio), which should be separately managed from livestock manure due to the negative impacts of manure nutrients and harmful effects on down-stream in the livestock manure process with respect to the microbial growth. Simultaneous nitrification and denitrification (SND) is linked to inhibition of the second nitrification and reduces around 40% of the carbonaceous energy available for denitrification. Thus, this study was conducted to find the optimal operational conditions for the treatment of MCW using an attached-growth biofilm reactor; i.e., nitrogen loading rate (NLR) of 0.14, 0.28, 0.43, and $0.58kg\;m^{-3}\;d^{-1}$ and aeration rate of 0.06, 0.12, and $0.24\;m^3\;h^{-1}$ were evaluated and the comparison of air-diffuser position between one-third and bottom of the reactor was conducted. Four sand packed-bed reactors with the effective volume of 2.5 L were prepared and initially an air-diffuser was placed at one third from the bottom of the reactor. After the adaptation period of 2 weeks, SND was observed at all four reactors and the optimal NLR of $0.45kg\;m^{-3}\;d^{-1}$ was found as a threshold value to obtain higher nitrogen removal efficiency. Dissolved oxygen (DO) as one of key operational conditions was measured during the experiment and the reactor with an aeration rate of $0.12\;m^3\;h^{-1}$ showed the best performance of $NH_4-N$ removal and the higher total nitrogen removal efficiency through SND with appropriate DO level of ${\sim}0.5\;mg\;DO\;L^{-1}$. The air-diffuser position at one third from the bottom of the reactor resulted in better nitrogen removal than at the bottom position. Consequently, nitrogen in MCW with a low C/N ratio of 2.15 was successfully removed without the addition of external carbon sources.

• Ocean Science Journal
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• v.42 no.4
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• pp.223-230
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• 2007

To understand the origin and biogeochemistry of the organic matter in surface sediments of Lake Shihwa and Lake Hwaong, organic nitrogen, inorganic nitrogen, labile organic carbon, and residual organic carbon contents as well as stable isotope ratios for carbon and nitrogen were determined by KOBr-KOH treatment. Ratios of organic carbon to organic nitrogen $(C_{org}/N_{org})$ (mean = 24) were much higher than ratios of organic carbon to total nitrogen $(C_{org}/N_{tot})$ (mean= 12), indicating the presence of significant amounts of inorganic nitrogen in the surface sediments of both lakes. Stable isotope ratios for organic nitrogen were, on average, $5.2\%_{\circ}$ heavier than ratios of inorganic nitrogen in Lake Shihwa, but those same ratios were comparable in Lake Hwaong. This might be due to differences in the origin or the degree of degradation of sedimentary organic matter between the two lakes. In addition, stable isotope ratios for labile organic carbon were, on average, $1.4\%_{\circ}$ heavier than those for residual organic carbon, reflecting the preferential oxidation of $^{13}C$-enriched organic matter. The present study demonstrates that KOBr-KOH treatment of sedimentary organic matter can provide valuable information for understanding the origin and degradation state of organic matter in marine and brackish sediments. This also suggests that the ratio of $(C_{org}/N_{org})$ and stable isotope ratios for organic nitrogen can be used as indexes of the degree of degradation of organic matter.

• Journal of Wetlands Research
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• v.9 no.1
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• pp.123-131
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• 2007

Effect of nitrogen-load condition on hydrogen ($H_2$) production and bacterial community in a continuous anaerobic hydrogen fermentation were investigated. The slight $H_2$ production on extremely low nitrogen-load condition (C/N ratio: 180) at the start-up period. The highest $H_2$ production was obtained when the C/N ratio was 36, the $H_2$ production yield ($mol-H_2/mol-glucose$) reached to 1.7, and it was indicated that Clostridium pasteurianum mainly contributed to the $H_2$ production. The $H_2$ production was decreased on both the lower (C/N: 72) and higher (C/N: 18) nitrogen-load conditions. The excess nitrogen-load was not always suitable for the hydrogen production. The fluctuation of $H_2$ production seemed to be caused by a change in the bacterial community according to the nitrogen-load condition, while a recovery of $H_2$ productivity was possible by a control of nitrogen-load condition through the bacterial community change. When the nitrogen-load condition was not suitable for hydrogen production, the lactic acid concentration was increased and also lactic acid bacteria were definitely detected, which suggested that the competition between hydrogen fermentator and lactic acid producer was occurred. These results demonstrated that the nitrogen-load condition affect on the $H_2$ productivity through the change of bacterial community in anaerobic hydrogen fermentation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.1
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• pp.1-6
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• 1991

A field experiment was conducted to find out the effects of nitrogen and potassium rates on the chemical constituents and physical properties of burley tobacco (1988； Burley 21. 1989； Burley 21 and KB 101) during successive two years. KB 101 was low in total nitrogen and total alkaloid contents and potassium/total nitrogen ratio of cured leaf. but high in the lightness, red and yellow color and filling power, comparing to Burley 21. The increasing rates of total nitrogen and total alkaloid contents were larger when nitrogen applied to 22.75kg/10a, but they were smaller when nitrogen applied above 22.75 kg/l0a. The potassium content, potassium/total nitrogen ratio, filling power and shatter resistance index of cured leaf were decreased by nitrogen fertilizer addition. The potassium content and shatter resistance index were increased by potassium fertilizer addition. The effect of nitrogen rate on the potassium/total nitrogen ratio of cured leaf was larger than the effect of potassium rate. When the nitrogen fertilizer being applied above 22.75 kg/l0a, there were no advantageous effects on the chemical and physical properties. It is considered to be sufficient that the potassium application is about 35.0 kg/l0a.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.909-917
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• 2021

This study was carried out experimentally on the production and properties of silicon nanopowders characteristics using a transferred type arc plasma apparatus. To investigate the properties of silicon nanopowder, the purity of argon gas(99.999%, 99.9%) and the partial pressure ratio of nitrogen gas(0~90%) were varied. The total pressure in chamber is 400Torr and the silicon chunk amount used as raw material is 300g. The power supplied to the cathode to generate arc plasma was 9~12kW/h, and the electrode was made of tungsten and graphite with a diameter of 13mm. The particle size, impurity elements and powder evaporation rate of the silicon powder were analyzed using the XRD, FE-SEM, TEM and electronic scale. According to the purity of argon gas, the silicon evaporation rate and the particle size were similar, and impurities were generated more in the case of 99.9% purity than 99.999%. When argon gas and nitrogen gas were mixed in the chamber, the silicon evaporation rate and particle size increased as the partial pressure ratio of nitrogen gas increased. In particular, when the partial pressure ratio of nitrogen gas was 80%, the silicon evaporation rate 80g/h, and the particle size was about 80~100nm.

• Journal of Welding and Joining
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• v.20 no.3
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• pp.91-97
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• 2002

Variation of HAZ toughness of Ti-containing steel with nitrogen content was investigated and interpreted in terms of its microstructure and the amount of soluble nitrogen present. The amounts of Ti and Al combined in TiN and AlN, respectively, in HAZ at $1400^{\circ}C$ peak temperature were less than those in base plate; 55~88% in TiN and 21~28% in AlN, indicating the dissolution of nitrifies in HAZ. The calculated amounts of soluble nitrogen using the thermodynamic analysis showed a good agreement with the measured values in other experiment. Therefore, the analysis can be used to estimate the amount of soluble nitrogen in HAZ. Simulated HAZ toughness was influenced not only by its microstructure but also by the amount of soluble nitrogen present after the formation of BN during the cooling cycle of welding. It showed maximum value when the nitrogen content is in stoichiometric ratio with titanium content, showing that soluble nitrogen in HAZ is detrimental to its toughness.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1222-1227
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• 2005

Optimal sludge recycling ratio for maximum total nitrogen(TN) removal efficiency was calculated stoichiometrically using nitrification and denitrification reaction with given influent water qualities in anoxic-oxic process which was one of the popular nitrogen removal system. The water quality items for stoichiometric calculation were ammonia, nitrite, nitrate, alkalinity, COD, and dissolved oxygen which could affect nitrification and denitrification. Optimal sludge recycling ratio for maximum TN removal efficiency was expressed by those five influent water qualities. TN concentration calculated stoichiometrically had kept good relationship with reported TN concentration in each tank and final effluent. In addition, it was possible to expect the TN concentration in final effluent by stoichiometric calculation within ${\pm}5.0\;mg/L$.