• Journal of Korean Society on Water Environment
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• v.22 no.5
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• pp.905-912
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• 2006

In this paper, simulation methods of the system dynamics model developed by Das et al. (1997) for activated-sludge wastewater treatment plants are illustrated in an attempt to determine the operating rules and the policies related to capacity expansion of an activated-sludge wastewater treatment plant. For existing conditions, the analyses were performed by varying activated-sludge return rate to observe changes in effluent water quality and treatment efficiency. The effluent water quality is also analyzed for various average daily inflow conditions and activated-sludge return rates. As a result, without expanding the aeration tank, maximum average daily inflow that can satisfy the effluent water quality standard of BOD $0.02kg/m^3$ was determined as $2,840m^3/hr$, subject to 100% of activated-sludge return rate while other factors remain constant. When the activated-sludge return rate is less than 100%, expansion of the aeration tank is necessary and minimum sizes of the aeration tank to satisfy the effluent water quality standard were determined for various activated-sludge return rates. In addition, the total operating and maintenance as well as unit treatment cost regression equations for activated-sludge wastewater treatment plants are suggested by using the cost data that are obtained from Water and Wastewater Division, Ministry of Environment. The regression analyses showed that the economies of scale phenomena exist in the operating and maintenance costs of activated-sludge wastewater treatment plants.

• Clean Technology
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• v.8 no.2
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• pp.93-99
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• 2002

Adsorption dynamics for toluene and trichloroethylene with an isothermal fixed bed of activated carbon fiber were investigated. Equilibrium isotherms were measured by a static method for toluene and trichloroethylene onto activated carbon fiber at temperatures of 298, 323, and 348 K and pressure up to 3 kPa for toluene and 6 kPa for trichloroethylene, respectively. These results were correlated by the Toth equation. And dynamic experiments in an isothermal condition of 298 K were examined. Breakthrough curves reflected the effects of the experimental variables such as partial pressures for adsorbate and interstitial bulk velocities of gas flow. To present the column dynamics, a dynamic model based on the linear driving force (LDF) mass transfer model was applied.

• Journal of Microbiology and Biotechnology
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• v.17 no.10
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• pp.1704-1707
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• 2007

Monitoring of the phage-host system of Microlunatus phosphovorus indigenous in activated sludge was attempted. A laboratory-scale activated sludge process was operated for 5 weeks with synthetic wastewater. The phage-host system population in the process was monitored by plaque assay and FISH methods at every 3 days. During the process operation, the phage-host system populations were more or less steady, except for 1 week in the middle of the operation. In that period, initially M. phosphovorus decreased significantly and its lytic bacteriophages increased, and then M. phosphovorus increased back to its original level while its lytic bacteriophages decreased. This observation suggests that lytic bacteriophages should be considered as one of the biological factors affecting the bacterial population dynamics in activated sludge processes.

• Journal of Environmental Science International
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• v.10 no.3
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• pp.239-245
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• 2001

This research was performed to investigate the dynamics of microbial community by RBC (Rotating Biological Contactor) using Rhodococcus sp. EL-GT and activated sludge. Cell counts revealed by DAPI were compared with culturable bacterial counts from nutrient agar. Colony counts on nutrient agar gave values 20~25% and 1~15% of cell counts (DAPI). The cell counts for the dynamics of bacterial community were determined by combination of in situ hybridization with fluorescently-labelled oligonyucleotide probes and epifluorescence microscopy. Around 90~80% of total cells visualized DAPI were also detected by the bacteria probe EUB 338. For both reactors proteobacteria belonging to the gamma subclass were dominant in the first stage (1 and 2 stage) and proteobacteria belonging to the gamma subclass were dominant in the last stage (3 and 4 stage).

• Proceedings of the Microbiological Society of Korea Conference
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• 2003.05a
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• pp.111-114
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• 2003

The dynamics of microbial community structure of the various domestic wastewater treatment processes were examined using a novel approach of quinone profiles. The compositions of microbial quinone of 5 sites fer plant and lab-scale activated sludge were analyzed. More than 14 kinds of quinones were observed in the activated sludges tested in this study. The microbial community structure of the plant activated sludge processes a little differed from that of the lab-scale submerged MBR systems. The dominant quinones were UQ-8, UQ-10 followed $MK-8(H_4)$, MK-7 and MK-6. The molar ratio of ubiquinones to menaquinones (UQ/MK) changed from 0.81 to 1.9, indicating that aerobic bacteria dominated the microbial community of the activated sludge examined. The microbial diversity of the activated sludges calculated from the all quinone compositions was 9.5-11.9 and the microbial equability of the activated sludges was 0.64-0.79.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.416-424
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• 2007

In adsorption/catalytic process, numerical analysis has been performed to identify the flow characteristics of flue gas in the cyclone and to estimate the residence time of activated carbon using Computational Fluid Dynamics (CFD) technique. To consider flue gas and activated carbon particles simultaneously, Euler-Lagrangian model was employed so that residence time could be obtained from the numerical analysis directly. The numerical analysis has been performed with different three particle sizes and compared each flow characteristics with particle’ size. Fundamental flow patterns of flue gas and activated carbon particles, pressure distribution, residence time of flue gas, and activated carbon particles and distribution of activated carbon have been obtained from the numerical analysis.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1087-1094
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• 2008

This article presents a multi-scale simulation approach starting from the molecular level for the adsorption process development, specifically, in n-hexane adsorption on activated carbon. A grand canonical Monte-Carlo(GCMC) method is used for the prediction of adsorption isotherms of n-hexane on activated carbon at the molecular level. Geometric effects and hydrodynamic properties of the adsorption column are examined by means of the two dimensional CFD(computational fluid dynamics) simulation. The adsorption isotherms from the molecular simulation and the axial diffusivity from the CFD simulation are exploited for the process simulation where the elution curve of n-hexane is obtained. For the first moment(mean residence time) of the pulse-response with respect to temperature and flowrate, the process simulation results obtained from this three-steps multiscale simulation approach show a good agreement with experimental data within 20% of maximum difference. The multi-scale simulation approach addressed in this study will be useful to accelerate the adsorption process development, while reducing the number of experiments required.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.2
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• pp.203-213
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• 2007

Numerical analysis has been performed to understand flow characteristics in the reactor with bag filters in an integrated adsorption/catalytic process which can treat dioxin and $NO_{x}$ together. Computational fluid dynamics technique was employed with Euler-Lagrangian model to consider flue gas and activated carbon particles simultaneously, so that residence time of flue gas and activated carbon particle could be obtained from the numerical analysis directly. The numerical analysis has been performed with different three particle sizes and compared each flow characteristics with particle's size. Fundamental flow patterns of flue gas and activated carbon particles, pressure distribution, residence time of flue gas and activated carbon particles, and distribution of activated carbon have been obtained from the numerical analysis. Flow patterns of flue gas and activated carbon particles in the reactor were very complicated and they moved along very various paths. Therefore, their residence time in the reactor was also various. The results obtained would be effectively used to estimate the removal efficiency in the reactor once the residence time is combined with the reaction equation.

• Journal of Korean Society on Water Environment
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• v.26 no.3
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• pp.491-496
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• 2010

This study aimed to obtain equilibrium concentration on adsorption removal of phosphorus by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical properties of activated carbon and dynamics of phosphorus removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. Phosphorus adsorption equilibrium reaching time of powdered activated carbon was reduced as the dosage of activated carbon increases, while granular activated carbon despite increased dosage did not have influence on adsorption equilibrium reaching times of phosphorus as well, taking more than 10 hours. It was also noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon on phosphorus was 4.26 which is bigger than those of granular activated carbon. The adsorption rate constant on phosphorus of powered activated carbon with low effective diameter and iodine number was highest as $8.888hr^{-1}$ and the effective pore diffusivity ($D_e$) was lowest as $2.45{\times}10^{-5}cm^2/hr$, and the value of phosphorus adsorption rate constant of granular activated carbon was $0.174{\sim}0.372hr^{-1}$, It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter was better and its rate constant was also high.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.311-316
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• 2008

This study aimed to obtain equilibrium concentration on adsorption removal of ammonia nitrogen by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical characteristics of activated carbon and dynamics of ammonia nitrogen removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. It was noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon was $4.6{\times}10^{-8}$ which is bigger than that of granular activated carbon. The adsorption rate constant on ammonia nitrogen of powered activated carbon with high porosity and low effective diameter was highest as 0.416 hr-1 and the effective pore diffusivity ($D_e$) was lowest as $1.17{\times}10^{-6}cm^2/hr$, and the value of ammonia nitrogen adsorption rate constant of granular activated carbon was $0.149{\sim}0.195hr^{-1}$. It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter and bigger porosity was better and its rate constant was also high. With a little adsorbent dosage of 2 g, there was no difference removal ability of ammonia nitrogen as change of adsorption properties.