• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.17-24
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• 2005

This study was carried out to investigate the removal efficiency of an intermittently aerated nonwoven fabric filter bioreactor fed continuously with domestic sewage. The hydraulic retention time(HRT) of the reactor was reduced from 12 hrs to 10 hrs to 8 hrs during an experimental period of 17 months. In order to search an optimum aeration/nonaeration time ratio for the nitrogen removal at each HRT, the cycle times of 3, 2 and 1 hr were tested at the aeration/nonaeration time ratio of 1. Then, the aeration/nonaeration time ratio was changed from 50 min/70 min to 40 min/80 min to 30 min/90 min at the cycle time of 2 hr which showed the best nitrogen removal. During the experimental period, the effluent SS concentration was always below 1.2 mg/L with more than 95% of BOD removal efficiency. The highest nitrogen removal of 90.1% was observed at the aeration/nonaeration time ratio of 40 min/80 min at the HRT of 10 hr. Oxidation-reduction potential could represent the degree of the nitrification and denitrification reaction in the reactor.

• Journal of Environmental Health Sciences
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• v.34 no.3
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• pp.233-239
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• 2008

In order to improve reactor performance of existing sewage treatment plants, the feasibility of enhancing reactor performance by bioaugmentation using EM as bioaugmentation agent and the effects of anoxic: oxic time ratio on reactor performance were investigated. Continuous and intermittent aeration modes were compared under the 6 hr of HRT. Three different types of intermittent aeration modes, that is, 15 min, of anoxic:45 min of oxic, 30 min of anoxic: 30 min of oxic, and 45 min of anoxic: 15 min oxic respectively were chosen as test modes to study the effects of anoxic : oxic time ratios on reactor performance. The optimum anoxic: oxic time ratio was 30 min:30 min when considering simultaneous removal of organic, nitrogen and phosphorus. When applying EM into a continuously aerated reactor under the varying dosing rates of 50-200 ppm, reactor performance in terms of organic and nitrogen removal efficiencies was not improved at all. Nitrogen removal efficiency was increase when the EM dosing rate was increased. However the degree of improvement was slight when the EM was injected above 100 ppm. However optimum phosphorus removal was found at the EM dosing of 200 ppm. Thus it was found that optimum injection concentration of EM is 200 ppm. It is apparent that putting EM into a sewage treatment plant significantly affects the T-N removal efficiency of the reactor by enhancing denitrification efficiency especially in operational conditions of relatively long anoxic periods. To achieve reciprocal condition in a reactor with intermittent aeration it is necessary to enhance the reactor performance by EM injection. In the case of modifying existing continuously aerated reactors into intermittent aerated reactors, it is obvious that operating costs of aeration would be reduced by reducing aeration time when compared with existing conventional sewage treatment plants.

• Membrane Journal
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• v.15 no.1
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• pp.70-83
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• 2005

By supplying air intermittently in various mode, the effects of oxic/anoxic time ratio and air scrubbing in aeration condition on the membrane flux and permeability were investigated. When suction pump stops, vacuum pressure remains inside the suction pump. Therefore, the effect of remaining vacuum pressure in the suction pump on fouling of membrane was investigated. The effect of EPS (Extra cellular Polymeric Substance) which is generated due to the long SRT and high concentration of MLSS and the dose of coagulant on the membrane were also investigated. The suitable oxic/anoxic time ratio for the best removal efficiency of organic matter and nitrogenous matter was 40 minutes (Oxic) : 20 minutes (Anoxic). At this time ratio, alum was dosed into the aeration tank. The result of dosing alum was that the concentration of alum solution might affect nitrification and denitrification. To remove 1 mg/L of phosphorus in MBR process, it needs 0.75 mg/L of alum solution.

• Journal of Korean Society on Water Environment
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• v.20 no.1
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• pp.18-23
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• 2004

In this research, a 2-stage intermittently aerated activated sludge system(IA) and intermittently aerated dynamic flow activated sludge system(DF) were investigated for the removal of nutrients in domestic wastewater. Wastewater was characterized by low C/N( organics/nitrogen) ratio. $COD_{cr}$, $BOD_s$, TKN and TP concentrations of domestic wastewater were 235, 47, 32 and 5.4 mg/L, respectively. Three sets of IA and one set of DF were operated. Three of four systems were added with fermented settled sludge taken from primary settling tank as an external electron donor and the other(IA) for control reactor was operated without addition of electron donor. All systems were operated at same sludge retention time of 20 days and hydraulic retention time of 12hrs. The supplemental electron donor was supplied into the anoxic mode. A higher denitrification rate was observed from the reactors with fermented settled sludge as an electron donor for denitrification compared to that of without addition of organic source. The result of this study indicates that the settled primary sludge, if the fermented at the acid stage, was an excellent electron donor for denitrification. 81 % of TN and 80% of TP were removed from the systems with the supplemental organic source added. However, the control reactor without addition of electron donor showed only 39% of TN and 43% of TP.

• Journal of Korean Society of Water and Wastewater
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• v.16 no.6
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• pp.679-685
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• 2002

The objective of this study was investigated for the microbial community structure and treatment performance of domestic wastewater in lab-scale submerged membrane bioreactor operated with anoxic-oxic cycles. Respiratory quinone profiles were applied as tools for identifying different bacterial populations. The cycle time program of bioreactor was control under anoxic/oxic of 60/90 minutes with an hydraulic retention time of 8.4 hrs. The average $COD_{Cr}$ removal efficiency of domestic wastewater was as high as 93%. The results showed complete nitrification of $NH_4^+$-N generated during oxic period and up to 50% of the total nitrogen could be denitrified. The dominant quinone types of suspended microorganisms in bioreactor were ubiquinone (UQ)-8, -10, followed by menaquinone (MK)-6, and MK-7 for anoxic period, but those for oxic period were UQ-8, MK-6, followed by UQ-10 and MK-7. The microbial diversities of bioreactor at anoxic and oxic periods, calculated based on the composition of all quinones were 10.4 and 12.2-11.8, respectively. The experimental results showed that the microbial community structure in the submerged membrane bioreactor treating domestic wastewater was slightly affected by intermittent aeration.

• Journal of the Korea Organic Resources Recycling Association
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• v.13 no.4
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• pp.136-147
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• 2005

Leachate from landfill sites contains high organics, chloride and ammonium nitrogen in concentration which might be potentially major pollutants to surface and groundwater environment. Most of landfill leachate treatment plants in Korea consist of biological processes to remove BOD and nitrogen. However, the efficiencies of refractory organics removal, nitrification and denitrification have not met frequently the national effluent regulation of wastewater treatment facility, especially in winter season. Simultaneous removal of organics and nitrogen from leachate is strongly necessitated to meet the national regulation on effluents from leachate treatment facilities. The intermittently aerated biological activated carbon fluidized bed(IABACFB) process was applied to treat real landfill leachates containing refractory organics and high concentration of ammonium nitrogen. The IABACFB reactor consisted of a single bed in which BAC fluidizing and an aerating column. The fluidized bed is intermittently aerated through the blower located at the aerating column. Experiments were performed to evaluate the applicability of Intermittently Aerated BACFB for simultaneous removal of refractory organic carbon and ammonium nitrogen of leachate. Organics and ammonia nitrogen($NH{_4}{^+}-N$)are oxidized during the aerobic stage, and nitrite-nitrate nitrogen($NO{_x}{^-}-N$) are removed to nitrogen gas through denitrification reaction during anoxic state. The IABACFB reactor condition reached a steady state within 40 days since the reactors had been operated. The blowing mode of 60 min.-On/60 min.-OFF is more compatible to remove TOC and ($NH{_4}{^+}-N$) operated. The blowing mode of 60 min.-On/60 min.-OFF is more compatible to remove TOC and ($NH{_4}{^+}-N$) simultaneously than the mode of 30 min.-On/90 min.-OFF. The average removal efficiencies of TOC, the refractory organic carbon, and the average efficiencies of nitrification and denitrification were 90%, 75%, 80%, 95%, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.1
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• pp.132-137
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• 2003

This study was carried out to investigate removal character of nitrogen and phosphorus with injection time of acetic acid on SBR, which is one of the biological treatment process. Wastewater used in experiment period was swine wastewater with character, relatively lower organic material concentration than nitrogen concentration. In the experiment with injection time of acetic acid, run 1 wasn't injected acetic acid during the anoxic period, and run 2 was injected intermittently acetic acid during the anoxic period of 15 hours. And run 3 was injected intermittently during the anoxic period of 3hours from end of wastewater filling. And filing time of the wastewater was 20hour from run 1 to run 3. In the study, the highest removal efficiency of organic and nitrogen were obtained by the operating condition of Run 2(the ratio of mixing/aeration time : 16.5/5.5, injection time of acetic acid : 15hours) and T-P was obtained by the operation condition of Run 3(the ratio of mixing/aeration time : 16.5/5.5, injection time of acetic acid : 3hours),and removal efficiency 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.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.1
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• pp.25-30
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• 2005

In order to decrease the high costs of membrane process, we have tried to develop two alternatives to membrane; a cartridge type filter and a metal membrane were tested for the high permeation flux with low cost and low energy. This research mainly focused on three points; 1) operation with high permeation flux by using of a cartridge type filter and a metal membrane, 2) removals of the filterable organic materials (FOC) by pretreatments for the membrane fouling control, and 3) advanced wastewater treatment by SMBR process with intermittent aeration and high MLSS. An Intermittently aerated membrane bioreactor using a submerged micro filter (cartridge type) was applied in laboratory scale for the advanced wastewater treatment. To minimize membrane fouling, intermittent aeration was applied inside of the filter with $3.0kg_f/cm^2$. The experiments was conducted for 6 months with three different HRTs (8, 10, 12 hr) and high MLSS of 6,000 and 10,000mg/L. The filtration process could be operated up to 50 days with permeation flux of 500LMH. Regardless of the operating conditions, more than 95% of COD, BOD and SS were removed. Fast and complete nitrification was accomplished, and denitrification was appeared to be the rate-limiting step. More than 75% T-N could be removed due to the endogenous denitrification. T-P removal efficiency was increased to 80% under the condition of MLSS 10,000mg/L.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.647-651
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• 2004

In this study, some of bacterial growth kinetic parameters were delineated and evaluated for the biological nutrient removal processes such as the $A^2/O$, 4stage-BNR, Intermittent Cycle Extended Aeration System(ICEAS) and Intermittently Aerated Cylindrical Oxidation Ditch(IACOD) processes. $Y_H$ values for the ICEAS process ranged from 0.71 to 0.74, and were higher than those for the other processes. It seems to indicated that organic carbons uptaked by microorganism were more used up for cell synthesis rather than for energy components in the ICEAS process. $b_H$ for the ICEAS and IACOD processes were lower than those for $A^2/O$ and 4stage-BNR processes. The $\mu_{max{\cdot}A}$ for the ICEAS was higher than those for the other processes, which indicated that desirable operating conditions for nitrifying bacteria's growth were established.

• Korean Journal of Environmental Agriculture
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• v.21 no.2
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• pp.136-143
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• 2002

Emission of methane and nitrous oxide affected by nitrogen fertilizer materials were measured simultaneously in rice paddy fields under flooding and intermittent irrigation in 2000. Studies focused on mitigating $CH_4$ emission from rice paddy fields are summarized and the possibilities and limits applied to world's rice cultivation are discussed. The mitigation options are water management, soil amendments, organic matter management, different tillage, rotation, and cultivar selection. Altering water management, in particular promoting midseason aeration by short-term drainage, is one of the most promising strategies, although these practices may be limited to the rice paddy fields where the irrigation system is well prepared. The test site was divided into two water managements: a continuously flooded plot which was maintained flooded by constant irrigation from May to September, and an intermittently drained plot in which short-term (20days) draining practices were performed one times during the flooding period. By total emission of GHGs converted by global warming potential (GWP), flooding plots were higher 170$\sim$208% than interimittent irrigation plots. For emission of GHGs in fertilizer materials, it was high in the order of Swine slurry>Urea+Rice straw>Urea>LCU. Basing on GHGs emission of urea fertilization under flooding as baseline GWP of urea fertilization and Latex-coated urea under intermittent irrigation showed lower GHGs emission by 41.4% and 55.8 respectively. In this case fertilizer use efficiency (kg unhulled rice/ of applied N) were 18.2$\sim$20.2 and 18.7$\sim$19.0 and 9.3 and 5.8$\sim$6.6 for Swine slurry and LCU and Urea+Rice straw and Urea in the continuously flooded and intermittently drained plot.