• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.206-214
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• 2005

This study was initiated to evaluate efficiencies of suspenced-growth processes(CAS; Conventional Activated Sludge, MLE; Modified Ludzack-Ettinger) and hybrid process(Modified-Dephanox) on removal of organic matter(C), nitrogen(N) and phosphorus(P) in municipal wastewater. M-Dephanox process was designed to improve the performance of Dephanox process on denitrification efficiency. As the results, removal efficiencies of total chemical oxygen demand(TCOD), total nitrogen(T-N) and total phosphorus(T-P) in M-Dephanox process, which is hybrid process, were 12,3, 18.6 and 28.2% higher than those in MLE, which is suspended-growth process. The better removal efficiencies of TCOD, T-N and T-P in M-Dephanox than those in MLE result that M-Dephanox is not only hybrid or multi-sludge process but also process using biosorption mechanism which is possible to use organics in denitrification, effectively. Ammonia removal efficiency in nitrification reactor of M-Dephanox was 96.7% at short hydraulic retention time(HRT) of 2 hr which was 3 hr more short HRT than that(HRT 5 hr) reported in other related papers. This indicates that M-Dephanox process can reduce HRT of whole process.

• Journal of Environmental Science International
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• v.6 no.4
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• pp.409-415
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• 1997

In order to Investigate the possibility as a simple technique of wastewater treatment for recirculating aquaculture system, the experiment by a biofilter unfit was carried out. The high and stable removal efficiency of nitrogen could be obtained by selecting the optimum recycle ratio and DO concentration. It was found that the proper combination of nitrifacation and denitrfication step in the reactor would be required for increasing the removal efficiency. The extent of nitrogen removal gradually decreased UO the rise of re- cycle ratio since the depression of denitrificatlon by the lack of hydrogen donor. The depression of nitrogen removal was overcome by increasing the CIN ratio In the wastewater. The extent of phosphorus removal was increased slightly with the increase of DO concentration and recycle ratio, but high removal efficiency was not observed. However, the extent of COD removal was not affected by recycle ratio and DO concentration and showed the stable removal of above 90%.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.39-46
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• 2014

The objectives of this study were to determine biodegradation and characteristics of BTEX and MTBE under aerovic-anaerobic conditions and evaluate the potential of natural attenuation method in denitrifying condition.. In the single-substrate experiments, all of the BTEX compounds were degraded under all the conditions. but, lower degradation of benzene and p-xylene were observed under aerobic condition due to the lack of oxygen initially supplied. In the mixed-substrate experiments, BTEX degradation was delayed compared to that in the single-substrate experiments due to a competition of the substrates. Biodegradation of MTBE was observed only under denitrifying conditions and we expected that MTBE mineralized to $CO_2$ without the accumulation of TBA. We also conducted to determine the effect of initial nitrate concentration on BTEX and MTBE degradation. At low nitrate concentration (<50 mg/L), BTEX degradations were limited by the lack of electron acceptor and BTEX degradation was inhibited at high nitrate concentration (>200 mg/L). The results in this study indicated that biotransformation could be applied to the gasoline-contaminated region under aerovic-anaerobic.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.527-537
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• 2009

Three sets of parallel MBRs (reactor No.1, reactor No.2, reactor No.3) maintaining an MLSS of 4,000 mg/L, 6,000 mg/L and 8,000 mg/L, respectively, were operated to investigate the effect of various HRTs and DO concentration of MBRs on the removal efficiency of organic matters and nitrogen. The HRTs were operated on 4 hr, 6 hr, 8 hr. DO concentrations were ranged 1.5~2.0 mg/L and 0.5~1.0 mg/L respectively on each HRT conditions. MBR was divided into an aerated part and non-aerated part by baffle placed under the water. DO concentrations were controlled by altering the position of baffle. In terms of TSS and CODCr, all systems had a similar level of the removal under varied HRTs and MLSS. TSS removal efficiency was more than 99% and CODCr removal was ranged 94~97% under all conditions. Under the same condition on the HRT and MLSS concentrations, DO concentrations did not affect the organic removal efficiency. On the nitrification efficiency, with high DO concentration, as HRT or MLSS increased, the slight increment of nitrification efficiency was observed. However, under the low DO concentration, increase of MLSS and HRT resulted in larger increase of the nitrification efficiency. At the same HRT and MLSS, the nitrification efficiency increased greatly with up to 16% as DO increased. When the HRT increased from 4hr to 8hr, the denitrification efficiency slightly increased under most of conditions. However, the increase of MLSS resulted in about 19~39% denitrification efficiency increment. MLSS concentrations showed great effect on the denitrification. The increase of the DO concentration at the same HRT and MLSS resulted in decrease of denitrification efficiency with up to 27%. In all systems, the denitrification efficiency had more influence on the TN removal efficiency than nitrification efficiency. So, MLSS concentration has greater effect on the TN removal than HRT and DO. The TN removal efficiency increased as MLSS increased with up to 37%. As a result, the highest TN removal efficiency was observed 79.0% at the condition showed the highest denitrification efficiency that DO of 0.5~1.0 mg/L, an HRT of 8 hr, and 8,000 mg/L of MLSS concentration were maintained.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.922-929
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• 2007

The complete oxidation of ammonia to nitrate is a distinctive two-step process divided into the oxidation of ammonia to nitrite(nitritation) by Nitrosomonas and the oxidation of nitrite to nitrate(nitratation) by Nitrobacter. The nitrogen removal via nitrite accumulation offers several advantages such as saving costs for aeration, saving carbon source and finally reduction of sludge discharge. In this work a suspended bioreactor coupled with membrane filtration(MBR) was used to find the process conditions of nitrite build-up. The MBR enables to reach sufficient nitrifying bacteria in the bioreactor, although the autotrophic bacteria can be easily washed out due to their lower growth rate. The dissolved oxygen concentration $c'_{O2}$ and ammonia concentration $c_{NH3}$ in the reactor were varied and investigated as parameters for nitrite accumulation. As a result the higher ammonia concentration in the reactor is very effective for starting nitrite build-up and the effect was strengthened in combination with lower dissolved oxygen concentration. With lower $c'_{O2}<0.3$ $mgL^{-1}$ $O_2$ and high $c_{NH3}=6.3\sim14.9$ $mgL^{-1}$ $NH_3N$ the 74% of the nitrite accumulation was achieved. Specially, it was found that the nitrite accumulation could occur not only in biofilm reactor as many references showed but also in the membrane bioreactor carried out in this study.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.1
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• pp.84-93
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• 2004

This study was performed : 1) to find the suitable HRT(hydralic retention time), 2) to evaluate the effects of the ratio of mixing/aeration time and injection time of external carbon source, for the removal of organics, nitrogen and phosphorus in swine wastewater by SBR(sequencing batch reactor process), which is one of the biological treatment process. The result of this study were summarized as follows : (1) As the ratio of mixing/aeration time was higher, $NH_4{^+}-N$ removal efficiency was increased and it was increased with increasing injection time of external carbon source because nitrification was affected by denitrification microbes propagation when injection time of external carbon soruce was shorted. T-N removal efficiency was increased with increasing the ratio of mixing/aeration time and injection time of external carbon source. (2) The T-P removal efficiency showed a great difference in each operating condition, and it was increased with increasing the ratio of mixing/aeration time increased and when the injection time of external carbon source was shorted because denitrification was done with effect by denitrification microbes propagation. (3) The highest removal efficiency of organic and nitrogen were obtained by the operating condition of Run 4-1(the ratio of mixing/aeration time : 16.5/5.5, injection time of external carbon source : 15hours) and T-P were obtained by the operation condition of Run 4-2(the ratio of mixing/aeration time : 16.5/5.5, injection time of external carbon source : 3hours), and efficiency(effluent concentration)of $BOD_5$, $COD_{Mn}$, $COD_{Cr}$, T-N and T-P in the treated water was 96.1%, 87.7%, 90.6%, 86.6% and 84.5%, respectively.

• Korean Journal of Environmental Agriculture
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• v.28 no.4
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• pp.371-377
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• 2009

In this study, simultaneous nitrification and denitrification (SND) from synthetic wastewater were performed to evaluate dissolved oxygen(DO) effects on chemical oxygen demand(COD) and nitrogen removal in a single membarne bio-reactor(MBR). DO levels in MBR at Run 1, 2, and 3 were 1.9~2.2, 1.3~1.6, and 0.7~1.0 mg/L, respectively. Experimental results indicated that DO had an important factor to affect COD and total nitrogen(TN) removal. SND were able to be accomplished in the continuous-aeration MBR by controlling ambient DO concentration. It is postulated that, because of the oxygen diffusion limitation, an anoxic micro-zone was formed inside the flocs where the denitrification might occur. From the results of this study, 96% of COD could be removed at DO of 0.7mg/L. At run 2 72.92% of nitrogen was removed by the mechanisms of SND (7.75mg-TN/L in effluent). In this study, SND was successfully occurred in a MBR due to high MLSS that could help to form anoxic zone inside microbial floc at bulk DO concentrations of 1.3~1.6mg/L.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.273-279
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• 2008

Space separation method that use independent reactor for nitrification and other reactor for denitrification has been commonly used for biological nitrogen removal process like $A^2O$ process. However, this method needs large space and complicate pipelines and time separation method such as SBR process have a difficulty in continuous treatment. Thus biological nitrogen removal process which is capable of continuous treatment, easy opeation and space saving is urgently required. In this research, submerged moving media was used for a biofilm process and suspended sludge was used for biological nitrogen removal at the same time. In particular DO environment by controlling air flow rate was investigated for simultaneous nitrification/denitrification. Total nitrogen removal in aeration rate more than $67L/min{\cdot}m^3$ showed 51~53% and rose to 65%, 70% and 78% in $50L/min{\cdot}m^3$, $58L/min{\cdot}m^3$ and $25L/min{\cdot}m^3$ respectively. Total phosphorus removal was very low about 10~20% more than $67L/min{\cdot}m^3$ aeration rates. But total phosphorus removal roses when reduces aeration rate by $58L/min{\cdot}m^3$ low and it showed total phosphorus removal of 72% in aeration rate $25L/min{\cdot}m^3$.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.4
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• pp.439-446
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• 2009

This study was performed to evaluate SND(simultaneous nitrification and denitrification)efficiency, nitrogen removal efficiency and filtration function of non-woven fabric by using submerging MBR packed with granular sulfur covered with non-woven fabric filter. Synthetic wastewater was used as influent wastewater. Concentration of $NH_4{^+}-N$ in influent was maintained about 40 mg/L and the experiment was performed in four phases according to the flow rate. Nitrogen loading rate divided four phases ranging from $0.04 kg\;NH_4{^+}-N/m^3-day$ to $0.16 kg\;NH_4{^+}-N/m^3-day$. As a result, the maximum $NH_4{^+}-N$ removal rate was accomplished at $0.142 kg\;NH_4{^+}-N/m^3-day$ in nitrogen loading of $0.147 kg\;NH_4{^+}-N/m^3-day$. Nitrification efficiency was higher than 95% in all phases. $NO_3{^-}-N$ loading rate was adjusted ranging from $0.22 kg\;NO_3{^-}-N/m^3-day$ to $0.89 kg\;NO_3{^-}-N/m^3-day$. The maximum $NO_3{^-}-N$ removal rate was accomplished up to $0.71 kg\;NO_3{^-}-N/m^3-day$ in $NO_3{^-}-N$ loading of $0.89 kg\;NO_3{^-}-N/m^3-day$. The maximum $NO_3{^-}-N$ removal efficiency was 95% in $NO_3{^-}-N$ loading of $0.22 kg\;NO_3{^-}-N/m^3-day$. T-N removal rate was 90% and concentration of T-N in effluent was 3.7 mg/L in T-N loading rate of $0.039 kg\;NO_3{^-}-N/m^3-day$. In this study, TMP in reactor with and without non-woven fabric filter were observed to define fouling of hollow-fiber membrane module. Reaching time to standard washing pressure(22 cm Hg) of two reactors were 29 days with non-woven fabric But the reactor without non-woven fabric reached standard washing pressure only after 4 days. Accordingly, non-woven fabric was demonstrated the superiority as a filtration ability. With high nitrogen removal rate and decreasing of fouling of membrane, MBR packed with granular sulfur covered with non-woven fabric filter submerging in activated sludge aeration tank can be used as an advanced treatment process.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.519-526
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• 2006

In this study, the major operating factors in SND(simultaneous nitrification and denitrification) using bioreactor packed with submerged cilia media and granular sulfur such as variation of nitrification rate, organic matter removal efficiency and denitrification efficiency in different DO concentration were mainly evaluated. Synthetic wastewater and actual sewage were used as influent wastewater. Experiment with synthetic wastewater as influent wastewater was divided into three phases with the adjustment of DO concentration. As the results, nitrification efficiency and T-N removal efficiency in the Phase 3(DO 1.0~2.0 mg/L) were 99% and 52.3%, which is significantly greater than those in other two phases. Also, loading rate and denitrification efficiency of SCPGS(Submerged Cilia media Packed with Granular Sulfur) were calculated as $0.44kg\;NO_3^--N/m^3-day$ and 50%, respectively. On the other hand, nitrification rate was decreased from 99% to 64% according to the DO concentration with the variation from 3.0~3.5 mg/L(phase1) to 0.4~0.6mg/L(phase2). Although the nitrification rate was decreased in 64% according to the variation of the DO concentration, T-N removal rate was rapidly increased to 49% by increasing of the denitrification efficiency. Experiment with actual sewage as influent wastewater was carried out to evaluate efficiency of SCPGS in real operation condition of full-scale sewage water treatment plant. At the time, T-N removal rate in this experiment and full-scale wastewater treatment plants were given by 43% and 20%, respectively. The above results indicate that SCPGS can be used as an advanced treatment process for economical efficiency considered.