• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.322-328
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• 2009

The advantage of simultaneous nitrification and denitrification (SND) is to reduce requirement of oxygen as well as tank volume. The fludized media was used in the oxic (aerobic) tank of Membrane-BNR to enhance the efficiency of SND. Nowadays, the interest of applying membrane to the wastewater treatment plant has been increased, which is proved by a lot of research published about the MBR. The Membrane-BNR, consisted of total 5 reactors might be called the compact process by using the fludized media and having short HRT of 6.5 hr. It could attain the further removal of not only the organics but also nutrients such as T-N and T-P. The mode A and B were identified with or without the step feed of influent. The mode A was classified with 3 modes according to the different DO concentration in the fludized media aerobic reactor, and the mode B with step feed was operated with the optimum DO condition. The step-feed was capable of improving TN removal efficiency under the domestic wastewater with the low ratio C/N. On the other hand, the efficiency of SND with the 1.0~1.5 mg/L DO in the oxic media tank was better than the one with below 1.0 mg/L, on which the nitrification did not happen enough, and with above 3.5 mg/L, on which the reduction of anoxic area in the tank happened. It means that the profitable nitrification should be performed prior to the denitrification step. The removal efficiency of nitrogen by SND was about 20% among of total denitrified nitrogen. And some organic carbon consumed could be reduced by the endogeneous denitrification.

• Journal of Wetlands Research
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• v.8 no.3
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• pp.79-89
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• 2006

The survival rate and tube number of Monocorophium uenoi, one of the dominant species in Lake Sihwa, was investigated under laboratory condition with salinity gradients (1, 5, 10, 15, 20, 25, 30, 35, 40‰). Another laboratory experiments were conducted to investigate the survival rate of Monocorophium uenoi in sulphide-rich sediment with oxic overlying water, and the effect of amphipod bioturbation on sulphide and oxygen profiles. The survival rate and tube-forming number of the amphipod were high in salinity range of 20 to 30‰. The amphipod survival rate was also high in sulphidic sediment when the water column was oxic. The amphipod bioturbation affected the oxygen and sulphide content in the sediment; oxygen conditions in the upper sediment layers were improved, and simultaneously the concentrations of sulphide were reduced. And their depth was clearly dependent on amphipod density. In Lake Sihwa, previously anoxic bottoms with sulphidic sediment during summer turn oxic with pycnocline disappearance during autumn. Amphipods seem to have the capability to quickly invade such areas, and their tubing of the sediment may play an important role in preparing the sediment for further recolonisation of other macrobenthos.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.5
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• pp.497-503
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• 2008

The Oxic-Settling-Anaerobic(OSA) process is a modified activated sludge processes for sludge reduction. It is evaluated that the sludge production in OSA process can decrease to 88% because of biomass decay and kinetic parameter($Y_H$ 0.237mgVSS/mgCOD, $b_H$ $0.195d^{-1}$) in anaerobic reactor, when compared with CAS process. However, it has problems caused by sludge reduction such as increase of nutrient loading. In case that the anoxic condition through the introduction of the intermittent aeration for the enhancement of nitrogen removal ability build up and enough rbCOD is suppled, maximum 88% of nitrogen is removed in the OSA process. If the OSA process optimizing the intermittent aeration cycle is applied to the separate sewage system with high rbCOD fraction, it can be converted to advanced process in terms of the sludge reduction and nitrogen removal, simultaneously.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.451-454
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• 2000

This study was carried out to investigate the effects of hydraulic backwash load and porous ceramic media on the biological nitrogen removal efficiencies of a biological aerated filter. An upflow anoxic-oxic biological aerated filter(AO-BAF) with porous ceramic media can remove nitrogen by nitrification and denitrification in single unit. After the AO-BAF backwash, nitrogen removal efficiency was lowest and gradually increased to the steady state. Nitrification efficiency, however, showed the opposite result. It is likely that the biofilms are exposed to aerobic condition as the excess biofilms were sloughed off by backwashing

• Korean Membrane Journal
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• v.3 no.1
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• pp.1-8
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• 2001

A lab-scale submerged membrane bio-reactor (MBR) with intermittent aeration was carried out for investigating the behavior of soluble microbial products (SMP). The SMP concentration of mixed liquor at Run 1 accumulated immediately at the end of running and biodegradable SMP converted into non-biodegradable SMP, but it did not occurred at the Run 2 and 3. The SMP formation coefficient (k) at the anoxic phase was a little higher than oxic phase, and the lowest k was investigated at Run 3. The combination of biological denitrification with the MBR Process was advantageous in the prevention of membrane bio-fouling.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.1
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• pp.19-25
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• 2018

The objectives of this study were to evaluate the removal characteristics of total nitrogen, the influence factor of denitrification and the optimum operating condition in the pigment wastewater treatment using PAC-A/O process. The operating conditions of PAC-A/O process were mean BOD volumetric loading $0.86kgBOD/m^3/day$, mean F/M ratio 0.072~0.13 kgBOD/kgMLVSS/day and mean C/N ratio 3.47, respectively. The conditions of anoxic process in the field plant test were mean pH 8.3~8.7 and mean temperature $34.1{\sim}44.0^{\circ}C$. The ORP bending point knee was eventually appeared in the ORP -107 mV and $NO_3{^-}-N$ removal efficiency was increased according to the ORP decrease. In the ORP -107 mV below condition, the removal efficiency of T-N and $NO_3{^-}-N$ was 92.3~95.0% and 98.5~99.7%. Denitrification rate was calculated to be 1.581~1.791 mg $NO_3{^-}-N/gMLSS/hr$. The experimental results showed that the ORP control in the PAC-A/O process could be an effective method for treatment of pigment wastewater.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.304-310
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• 2003

This study was conducted to estimate the internal dissolved organic carbon (DOC) loading from sediment in eutrophic shallow Lake Kasumigaura. Contents of water and organic carbon were about 80% and 6.3% with depth in the sediment, respectively. The highest DOC concentration in porewater (104 mg C/l) was observed in September suggesting that the porewater could play an important role as an internal loading of DOC. Results of DOC release experiments showed that the labile-DOC (L-DOC) release was not detected in the oxic condition, while refractory-DOC(R-DOC) release was detected. The L-DOC and R-DOC release rates in the anoxic codition ranged from 14.5${\sim}$ 48.6, 14.4 ${\sim}$27.3 mgC $m^{-2}$ $d^{-2}$, respectively. The current study showed that L-DOC released in the oxic condition was rapidly utilized by aerobic bacteria, in contrast, L-DOC and R-DOC released in anoxic codition were slowly utilized by anaerobic bacteria. These results suggested that L-DOC and R-DOC were closely related to sediment release and most of the R-DOC released could be an important source of DOC in eutrophic lakes during summer. Therefore, R-DOC pool should be added as one of the important energy source for microbial-based aquatic food webs in eutrophic lakes.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.450-455
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• 2005

To treat wastewater efficiently by a one-step process of nitrogen removal, a new strain of $N_2-producing$ bacteria from $NH{_4}{^+}$ under an aerobic condition was isolated and identified. By 16S-rDNA analysis, the isolate was identified as Enterobacter asburiae with 96% similarity. The isolate shows that the capacity of $N_2$ production under an oxic condition was approximately three times higher than that under an anoxic condition. The optimal conditions (pH, temperature and C/N ratio) of the immobilized isolate for $N_2$ production were found to be 7.0, $30^{\circ}C$ and 5, respectively. Under all the optimum reaction conditions, the removal efficiency of $COD_{Cr}$ and TN reached 56.1 and 60.9%, respectively. The removal rates of $COD_{Cr}$ and TN were highest for the first 2.5 hrs (with the removal $COD_{Cr}$ ratios of 32.1), and afterwards the rates decreased as reaction proceeded. For application of the immobilized isolate to a practical process of ammonium removal, a continuous bioreactor system exhibited a satisfactory performance at HRT of 12.1 hr, in which the effluent concentrations of $NH{_4}{^+}-N$ was measured to be 15.4 mg/L with its removal efficiency of 56.0%. The maximum removal rate of $NH{_4}{^+}-N$ reached 1.6 mg $NH{_4}{^+}-N/L/hr$ at HRT of 12.1 hr (with N loading rate of 0.08 $Kg-N/m^3-carrier/d)$. As a result, the application of the immobilized isolate appears a viable alternative to the nitrification-denitrification processes.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.571-576
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• 2004

Since anaerobic/anoxic/oxic process, which is a typical mainstream biological nitrogen and phosphorus removal process, utilizes influent organic matter as an external carbon source for phosphorus release in anaerobic or anoxic stage, influent COD/T-P ratio gives a strong influence on performance of phosphorus removal process. In this study, a bench scale experiment was carried out for SBR process to investigate nitrogen and phosphorus removal at various influent COD/T-P ratio and nitrate loadings of 23~73 and 1.6~14.3g $NO_3{^-}-N/kg$ MLSS, respectively. The phosphorus release and excess uptake in anoxic condition were very active at influent COD/T-P ratios of 44 and 73. However, its release and uptake was not obviously observed at COD/T-P ratio of 23. Consequently, phosphorus removal efficiency was decreased. In addition, the phosphorus release and uptake rate in anoxic condition increased as the nitrate loading decreased. Specific denitrification rate had significantly high correlation with organic materials and nitrate loadings of the anoxic phase too. The rate of phosphorus release and uptake in the anoxic condition were $0.08{\sim}0.94kg\;S-P/kg\;MLSS{\cdot}d$ and $0.012{\sim}0.1kg\;S-P/kg\;MLSS{\cdot}d$, respectively.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.322-335
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• 2003

Nutrient fluxes and sediment oxygen demands (SOD) were measured with intact sediment cores collected from three stations in the downstream of Nagdong River. The sediments were subjected to controlled oxic and hypoxic conditions and temperature gradients (from $10^{\circ}C$ to $30^{\circ}C$) of the overlying waters in laboratory batch system. The effect of temperature and labile layer thickness of the sediment on SOD were examined. $PO_4\;^{3-}$ and $NH_4\;^+$ fluxes were elevated above $20^{\circ}C$ and large mobilities were observed when they were coupled with a hypoxic and high-temperature condition. In the well oxygenated conditions, $PO_4\;^{3-}$ fluxes were negative or negligible but $NH_4\;^+$ fluxes ranged from 1.3 mg N $m^{-2}\;hr^{-1}$ to 2.3 $m^{-2}\;hr^{-1}$. Temperature quotients($Q_{10}$) of $PO_4\;^{3-}$ fluxes were 3.7 ${\sim}$ 7.3 ranges to have the most high values. $PO_4\;^{3-}$ and $NH_4\;^+$ fluxes had the logarithmic increase with temperature, while $NO_3\;^-$ was negatively absorbed to the sediment and linearly correlated with the temperature. $SiO_2$ fluxes showed no difference among oxic and hypoxic conditions and sediment texture. The nutrient fluxes would be closely correlated with pore water chemistry of sediments and activated by the top sediment layer composition such as labile organic matters or algal detritus. The ecological implications of the nutrient fluxes were discussed in terms of sources and sinks of nutrients coupled to algal productions in the Nagdong River.