• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.2
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• pp.125-131
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• 2003

This study was carried out to develop INSUB(Indirected Aerated Submerged Biofilter) which can remove organics, nitrogen and phosphorus with an advanced treatment system. The results were as followed in laboratory model experiment. As for treatment of sewage, when economical efficiency was considered in practice, the highest removal efficiency was at 18hr of HRT, 1.017m/hr of superficial velocity and 40% of media packing ratio. Each removal efficiency for $COD_{cr}$, $COD_{Mn}$, $BOD_5$, T-N, and T-P was 90.6, 85.3, 95.0, 52.3 and 56.8%. To remove the nitrogen and phosphorus With high efficiency, first of all, denitrification have to be completed, then uptake of phosphorus have to completed. Therefor, mixture of anoxic and aerobic reactor was necessary for the high removal efficiency of nitrogen and phosphorus in INSUB.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.2
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• pp.106-114
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• 1998

In this research, single-, two- and four-stage intermittently aerated activated sludge system were investigated for simultaneous removal of nitrogen and phosphorus with swine wastewater. For the comparison of removal efficiency, conventional activated sludge system was operated. Operational conditions of intermittently aerated activated sludge system were SRT 20day, HRT 24hr and aeration/nonaeration time 1hr/1hr, respectively. Nitrogen and phosphorus removal efficiency in Intermittently aerated activated sludge system was upgraded compare with conventional activated sludge system. In single-stage intermittently aerated activated sludge system, release-uptake of $PO_4^{3-}-P$ was observed very well but, phosphosrus removal in effluent was not effective. In single-stage intermittently aerated activated sludge system, release-uptake of $PO_4^{3-}-P$ in first reactor, was observed very well but, in following reactor, $PO_4^{3-}-P$ concentation showed almost no change. T-N removal efficiency in conventional activated sludge system, single-, two-, and four-stage intermittently aerated activated sludge system were 48, 87, 90.9 and 95.5%, respectively, and phosphorus removal efficiency were 48, 75, 97 and 95%, respectively. Intermittently aerated activated sludge system as a alternative processes of conventional system leads to meet satisfactory effleunt with only on/off aeration regulation and save energy for aeration.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1261-1265
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• 2002

This study was focused on the investigation of the characteristics of organics and nitrogen removal with the recycle ratio in anoxic/oxic(A/O) packed bed process that consisted of the anoxic reactor and the aerobic reactor. As increasing the recycle ratio by 0.5, 1.0, 2.0, the COD removal efficiency increased by 94.0%, 98.5%, 98.8% respectively. The aerobic reactor showed the perfect nitrification efficiency by 98.5%, 99.2%, 98.0% respectively. The T-N removal efficiency with the recycle ratio, increased by 56%, 67%, 70% respectively. As increasing the recycle ratio by 0.5, 1.0, 2.0, T-P removal efficiency decreased by 62.1%, 57.4%, 51.3% respectively. The process by releasing the stored phosphorus in the anoxic reactor and uptaking the excess phosphorus in the aerobic reactor, occurred well comparatively when recycle ratio is 0.5. But this process did not occur when the recycle ratio is 1.0 and 2.0. And optimum pH of nitrification was about 6~7 and alkalinity decreased as nitrification rate increased. As increasing the recycle ratio in the anoxic reactor, DO concentration and ORP increased.

• The KSFM Journal of Fluid Machinery
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• v.18 no.2
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• pp.43-47
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• 2015

As water quality regulations have tightened, many studies to improve wastewater treatment efficiency have been performed. In this study, magnetite powder was used to maintain a high concentration of MLSS in lab-scale wastewater treatment system. After magnetite powder injection, MLSS concentration was above 8,000 mg/L and it was 3.2 times higher than control group(2,500 mg/L). In addition, nitrogen removal efficiency and phosphorus removal efficiency comparing with the control group was increased 20.5% and 11%, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.6
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• pp.384-392
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• 2000

To establish N fertilizer recommended scheme for the Chinese cabbage cultivation in green house based on the soil test of nitrate nitrogen, relationship among the content of soil nitrate and fertilizer effects and fertilizer N use efficiency were investigated from nine soils which differed amount of nitrate nitrogen from $14mg\;kg^{-1}$ to$226mg\;kg^{-1}$. The amount of nitrate nitrogen in soil showed a positive correlation with the dry weight of chinese cabbage in the plot of no fertilization. When the fertilizer effects were calculated by difference between the plots of fertilization and no fertilization in the dry weight and the amount of N uptake, a negative correlation was obtained between the amount of nitrate nitrogen in soils and the fertilizer effects. There was also a negative correlation between the amount of nitrate nitrogen in soils and fertilizer use efficiency. Recommendation of application rate of nitrogen fertilizer based on content of $NO_3-N$ in soils was evaluated by the regression equation among the content of soil nitrate, fertilizer effects and fertilizer N use efficiency. Incase the content of $NO_3-N$ nitrogen in soil is more than $200mg\;kg^{-1}$, No N fertilization is recommended; However, The standard N fertilization($320kg\;ha^{-1}$) is recommended for the soils with less than $50mg\;kg^{-1}$. For the soils ranged from $50mg\;kg^{-1}$ to $200mg\;kg^{-1}$ in the amount of nitrate nitrogen, an equation has been developed in order to calculate the recommended amount of fertilizer N.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.1
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• pp.16-21
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• 2005

This study was conducted to establish the elaborate nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy. The nitrogen uptake by rice plants was insignificant until 25 days after seeding, and increased gradually thereafter. During this early growth stage, rice plants absorbed only the $4\%$ of basal applied N, while the $45\%$ of N fertilizer remained in the paddy soil. The absorption of basal N by rice plants was almost completed at 46 days after application. Nitrogen top-dressed at 5-leaf stage was well matched to crop nutrient demand, so it could be absorbed so actively in 8days after application. As a result, we could cut down the amount of N fertilizer to $36\%$ of the basal N level without significant difference in yield. Plant recoveries of fertilizer $^{15}N$ applied with different application timings were $7.8\%$ for basal, $9.4\%$ for 5-leaf stage, $17.1\%$ for tillering stage, and $23.4\%$ for panicle initiation stage, respectively. When urea was applied with nitrogen fertilization practice based on basal incorporation (BN), plant recovery of $^{15}N$ at harvest was $31.0\%$, which was originated from $13.7\%$ for grain, and $21.3\%$ of the fertilizer $^{15}N$ remained in the soil, and the rest could be uncounted. Plant recovery of fertilizer $^{15}N$ applied with nitrogen fertilization practice based on topdressing at 5-leaf stage (TN), where N rate was reduced by $18\%$ compared with BN, was $35.1\%$ (grain $15.6\%$), and $19.9\%$ of the fertilizer $^{15}N$ remained in the soil, and the rest could be uncounted. TN showed a higher $^{15}N$ recovery than BN because it was to apply N fertilizer at a time to well meet the demand of rice plant direct-seeded on flooded paddy. We concluded that TN would be the nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy.

• KSBB Journal
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• v.24 no.3
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• pp.291-295
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• 2009

This study performed verification experiment for the removal of total nitrogen in sewage from a Town M village sewage treatment plant using YPNR processes. The total nitrogen discharged after the denitrification process was maintained at a level of 8-15 mg/L, which results in the total nitrogen removal efficiency above 68% on average. The total nitrogen components in discharged water consisted of 16% of ammonia nitrogen, 6% of nitrite nitrogen, and 77% of nitrate nitrogen, which reaches a 95% nitrification efficiency. Hence, the YPNR advanced treatment process used in this study can be successfully applied to sewage treatment.

• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.465-472
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• 1999

To remove nitrogen oxides(NOx) in exhaust gas of diesel engine, three-way catalytic process with plasma discharger has great possibilities. Characteristics of NOx removal depends on NO conversion to NO$_2$and/or HNO$_3$due to high activation energies for NO oxidation and reduction. NOx removal efficiency by using three-way catalytic with plasma discharger indicated about 50% at 40watt power consumption condition.

• Journal of the Korean Applied Science and Technology
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• v.28 no.1
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• pp.6-9
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• 2011

Step feed process was analyzed stoichiometrically for the optimal operation conditions in this study. In case of optimal operation conditions, minimum R (sludge recycling) value, r (internal recycling ratio) value, and n (influent allocation ratio) value for the step feed process to acquire the maximum TN removal efficiency were identified by theoretical analysis. Maximum TN removal efficiency, based on stoichiometric reaction, can be obtained by controlling n value for the step feed process.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.755-760
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• 1999

To remove nitrogen oxides(NOx) in exhaust gas of diesel engine three-way catalytic process with plasma discharger has great possibilities. Characteristics of NOx removal depends on NO conver-sion to $NO_2$ and /or $HNO_3$ due to high activation energies for NO oxidation and reduction, NOx removal efficiency by using three-way catalytic with plasma discharger indicated about 50% at 40watt power consumption condition.