• Clean Technology
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• v.16 no.1
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• pp.39-45
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• 2010

In this paper, 4 bundle modules of PVDF hollow fiber membrane from Woori Tech company (Korea) were manufactured in a treatment capacity of 10 ton/day. A membrane bioreactor (MBR) pilot plant was installed at Sooyoung Wastewater Treatment Plant in Busan. An alternating aeration process was selected to avoid the concentration profile of suspended solid (SS) in the MBR. For stable operation, raw wastewater with mixed liquor suspended solid (MLSS) of about 1,000 ppm, which was in-flowed from the aeration tank of the wastewater treatment plant, was fed and filtered through the pilot plant. Subsequently the pilot plant were washed three times with washing water: once with ethanol solution, once with a solution of 5% NaOCl, and finally with washing water. After the chemical washing, the remaining water in the MBR was fed into the pilot plant. As a result, the SS removal efficiency was found to be more than 99.9%. The amount of filtrate with the aeration tank influent decreased by 16%, compared with that from the initial conditions, giving rise to 30% increase in the suction pressure. These results were used to set up continuous operation conditions. The results from the continuous operation with influent MLSS of 1,900 mg/L showed that the SS removal efficiency was about 99.99% and that the amount of filtrate and the suction pressure were $42{\sim}52L/m^2$ and 16~20 cmHg, respectively, indicating stable operation of the pilot plant. However, for the reuse of wastewater, methods need to be sought to avoid growth of algae which affects the SS removal efficiency at inlet and outlet of the permeate tank.

• Membrane Journal
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• v.14 no.4
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• pp.289-297
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• 2004

In this study, membranes were coupled to a sequencing batch reactor for simultaneous removal of organic matter and nitrogen, and the influences of MLSS (mixed liquor suspended solid) concentration and the sludge loading rate on membrane fouling and bioactivity were investigated. The amount of membrane fouling slightly increased with MLSS concentration at both non-aeration and aeration conditions, but effect of MLSS concentration was more significant at aeration condition. Although the effect of MLSS concentration on membrane fouling was found to be insignificant at low concentration level, extremely low sludge loading, which were generated by the maintenance of large amount of biomass in the reactor, caused severe membrane fouling, and air scouring effect decreased significantly in this condition. Specific bioactivity was constantly reduced as sludge loading rate decreased. In spite of high MLSS concentration over 17,000 mg/L, the activity of the reactor decreased at extremely low sludge loading rate presumably due to the lower oxygen transfer and the competition of biomass to deficient substrate.

• Membrane and Water Treatment
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• v.10 no.4
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• pp.307-311
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• 2019

The ejector type microbubble generator, which is the method to supply air to water by using cavitation in the nozzle, does not require any air supplier so it is an effective and economical. Also, the distribution of the size of bubbles is diverse. Especially, the size of bubbles is smaller than the bubbles from a conventional air diffuser and bigger than the bubbles from a pressurized dissolution type microbubble generator so it could be applied to the aeration tank for wastewater treatment. However, the performance of the ejector type microbubble generator was affected by hydraulic pressure and MLSS(Mixed Liquor Suspended Solid) concentration so many factors should be considered to apply the generator to aeration tank. Therefore, this study was performed to verify effects of hydraulic pressure and MLSS concentration on oxygen transfer of the ejector type microbubble generator. In the tests, the quantity of sucked air in the nozzle, dissolved oxygen(DO) concentration, oxygen uptake rate(OUR), oxygen transfer coefficient were measured and calculated by using experimental results. In case of the MLSS, the experiments were performed in the condition of MLSS concentration of 0, 2,000, 4,000, 8,000 mg/L. The hydraulic pressure was considered up to $2.0mH_2O$. In the results of experiments, oxygen transfer coefficient was decreased with the increase of MLSS concentration and hydraulic pressure due to the increased viscosity and density of wastewater and decreased air flow rate. Also, by using statistical analysis, when the ejector type microbubble generator was used to supply air to wasterwater, the model equation of DO concentration was suggested to predict DO concentration in wastewater.

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.772-779
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• 2005

Ammonia-oxidizing bacteria (AOB) were enriched by repeating fed-batch cultivations in an AOB-selective medium of activated sludges from a domestic wastewater treatment plant. Enriched culture showed strong capabilities of ammonia oxidation [0.810 mg $NH_4^+$-N/mg mixed liquor suspended solids (MLSS)$\cdot$day] as well as $NO_x^-$-N production (0.617 mg $NO_x^-$-N/ mg MLSS$\cdot$day). Degree of enrichment was examined through fluorescent in situ hybridization (FISH) analyses using an AOB-specific Cy3-labeled oligonucleotide probe (NSOl90) and terminal-restriction fragment length polymorphism (T-RFLP) analyses. FISH analyses confirmed that the fraction of AOB among 4',6-diamidino-2-phenylindole (DAPI)-stained cells increased from about less than $0.001\%$ to approximately $42\%$ after enrichment of AOB, and T-RFLP analyses showed that bacterial community became simpler as enrichment was continued. When the enriched culture of AOB was added (150 mg/l as dry suspended solid) to the normal activated sludge (3,000 mg/l as dry suspended solid), nitrification efficiencies were improved from 0.020 mg $NO_x^-$-N/mg MLSS$\cdot$day to 0.041 mg $NO_x^-$-N/mg MLSS$\cdot$day in a synthetic wastewater and also from 0.0007 mg $NO_x^-$-N/mg MLSS$\cdot$day to 0.0918 mg $NO_x^-$-N/mg MLSS$\cdot$day in a real domestic wastewater. Therefore, it is expected that this enrichment method could be used for improving efficiency of nitrification in wastewater treatment plants.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.222-228
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• 2010

Biological degradation of nitrogen-containing aromatic compounds was investigated in activated sludge previously adapted to mineralize low concentrations of nitrogen-containing aromatic compounds. Normally, the time required for 95% degradation of 10 mg/l dinitrophenol (DNP) under aerobic conditions was less than 4 hours without any lag, and with mixed liquor suspended solid (MLSS) levels from 600 to 1,000 mg/l. However, when the initial DNP concentration was increased to 75 mg/l, lags and even complete inhibition of DNP degradation were observed. The length of the lag was found to increase proportionally with decreasing MLSS levels. When dilute activated sludge was incubated for extended periods (192 hours), degradation of 75 mg/l DNP did eventually occur after lag periods of 37 to 144 hours, depending on the MLSS concentration. DNP was degradable in high concentrations if MLSS concentrations were sufficiently high to allow growth of bacteria resistant to the toxic effects of DNP.

• Journal of Environmental Science International
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• v.28 no.7
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• pp.607-615
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• 2019

The purpose of this study is to biological treatment of high salinity wastewater using Aerobic Granular Sludge (AGS). In laboratory scale's experiments research was performed using a sequencing batch reactor, and evaluation of the denitrification reaction in accordance with the injection condition of salinity concentration, surface properties of microorganisms, and sludge precipitability was performed. The results showed that the salinity concentration increased up to 1.5%, and there was no significant difference in the nitrogen removal efficiency; however, it showed a tendency to decrease gradually from 2.0% onward. The specific denitrification rate (SDNR) was 0.052 - 0.134 mg $NO_3{^-}-N/mg$ MLVSS (mixed liquor volatile suspended solid)${\cdot}day$. The MLVSS/MLSS (mixed liquor suspended solid) ratio decreased to 76.2%, and sludge volume index ($SVI_{30}$) was finally lowered to 57 mL/g. Using an optical microscope, it was also observed that the initial size of the sludge was 0.2 mm, and finally it was formed to 0.8-1.0 mm. Therefore, salinity injection provides favorable conditions for the formation of an AGS, and it was possible to maintain stable granular sludge during long-term operation of the biological treatment system.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.747-753
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• 2006

Air flotation is a solid-liquid separation process that utilizes up-flow microbubbles to thicken activated sludge and enhance clarification efficiency. Continuous air flotation experiments were performed to investigate the effect of operation parameters such as initial MLSS (mixed liquor suspended solid) concentration, air pressure, surface loading rate, air to solid (A/S) ratio, and flotation time on thickening efficiency. An initial activated sludge concentration ranged from 3,000 to 12,000mgSS/L and thickened sludge concentration varied from 6,400 to 28,100mgSS/L. The result showed that the thickening efficiency was mainly dependent on surface loading rate, A/S ratio, and flotation time. The pressure did not affect the thickening efficiency when it kept in the range of 1.6 to 1.8 bar. Experimental results showed that the thickening efficiency of activated sludge was increased only when the feed sludge concentration exceeded 5,000mgSS/L and the thickened concentration was over 20,000mgSS/L. At this time, SS concentration in the clarified liquid was ranged from 5 to 10mg/L.

• Journal of Environmental Science International
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• v.19 no.11
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• pp.1315-1322
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• 2010

A membrane bioreactor (MBR) was designed using polyvinylidene fluoride(PVDF)-type hollow fiber membrane modules with a treatment capacity of 10 ton/day. A pilot plant was installed in a sewage treatment plant and was operated with an intermittent aeration method which avoids any concentration gradient of suspended solids (SS) in the MBR. For continuous operation, the pilot plant was first tested with influent (mixed liquor suspended solid:MLSS of 1000-2000 mg/L) of aeration tanks in the sewage treatment plant. The MBR was pre-treated with washing water, 10% ethanol solution, 5% NaOCl solution and finally washing water, one after another. To demonstrate the effect of the MBR on sewage treatment, compared with conventional activated sludge processes, we investigated the relationships among permeate amount (LMH), change in operation conditions, influent MLSS level and sludge production. It was found that the optimum aeration rate and suction pressure were $0.3\;m^3$/min and 30~31 cmHg, respectively. Under stable conditions in aeration, suction pressure, influent flow rate and drainage, the SS removal efficiency was more than 99.99% even when the MLSS loading rate changes. Compared with conventional activated sludge processes, the MBR was more effective in cost reduction by 27% based on permeate amount and by 51.5% on sludge production.

• Journal of Environmental Science International
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• v.31 no.4
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• pp.295-309
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• 2022

The purpose of this study was to evaluate the operational characteristics of wastewater treatment using Sequencing Batch Reactor (SBR) with Aerobic Granular Sludge (AGS) separator in the pilot plant. Pilot plant experiments were conducted using SBR with AGS separator and pollution removal efficiencies were evaluated based on the operational condition and surface properties of AGS. The results of the operation on water quality of the effluent showed that the average concentration of total organic carbon, suspended solids, nitrogen, and phosphorus was 6.89 mg/L, 7.33 mg/L, 7.33 mg/L, and 0.2 mg/L, respectively. All these concentrations complied the effluent standard in Korea. The concentration of mixed liquor suspended solid (MLSS) fluctuated, but the AGS/MLSS ratio was constant at 86.5±1.3%. Although the AGS/MLSS ratio was constant, sludge volume index improved. These results suggested that the particle discharged fine sludge and increased the AGS praticle size in the AGS. Optical microscopy revealed the presence of dense AGS at the end of the operation, and particles of > 0.6 mm were found. Compared to those of belt-type AGS separator, the required area and power consumption of the hydrocyclone-type AGS separator were reduced by 27.5% and 83.8%, respectively.

• Environmental Engineering Research
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• v.24 no.2
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• pp.238-245
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• 2019

This study investigated the characteristic of aerobic granular sludge (AGS) process to treat the sewage having low carbon/nitrogen ratio (Biochemical oxygen demand ($BOD_5$):Total nitrogen (T-N), 4.5:1) in sequencing batch reactor (SBR). The removal efficiency of $BOD_5$, suspended solid (SS), T-N and phosphorus ($PO_4{^{3-}}$-P) were 92.6%, 64.3% and 90.1%. Concentration and size of AGS were changed in proportion to the organic matters and nitrogen concentration of the influent (Concentration and size of AGS: 1,700-3,000 mg/L, 0.5-1.0 mm). Mixed liquor suspended solid (MLSS) also changed with the concentration of AGS (MLSS: 2,000-3,500 mg/L). When the settling time was shortened from 15 min to 10 min, size and shape of AGS were maintained (Size of AGS: 1.0-1.5 mm). In addition, the concentration of AGS and MLSS increased (Concentration of AGS: 3,500 mg/L, MLSS: 4,000 mg/L). Concentration, size and shape of AGS were affected the settling time of the reactor more than the concentration of organic matter and nitrogen in the influent. In the results of removal efficiency and changes in AGS, we confirmed that the SBR process using AGS can be used to treat the sewage having low carbon/nitrogen ratio by applying short settling time.