• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.113-133
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• 1998

In activated sludge process, sludge settling condition is affected by organic loading rate or operation condition, and if settling condition is getting worse, it is common that overall process fails due to wash-out of biomass causing low concentration in the aeration tank. Also activated sludge process has such several problems as requiring large area, consuming a lot of power and producing large volume of sludge. Increased public concern over health and the environment combined with a strong desire to reduce capital, operating and maintenance costs, have created a need for innovative technologies for building new high quality effluents which vail meet 21st century crkeria. MBR(Membrane Bioreactor) process consists of a biological reactor and ultrafiltration(UF) membrane system that replaces the conventional clarifier of an activated sludge process. The main operating advantages of this system are that the quality of the effluent is independent of the settleability of the mixed liquor and that the effluent is free of suspended solids in any operating condition. It is possible to eliminate clarifier and to reduce the volume of aeration tank because it can afford to accumulate high biomass concentration in the bioreactor(20, 000~30, 000mg/L), which would not be possible in a conventional activated sludge process. Therefore, this process reduces overall treatment plant area. In addition to those advantages, Longer SRT condition enables higher sludge digestion in MBR process so the sludge volume produced is 50 to 70% lower than that of conventional activated sludge process There are two kinds of MBR process according to the allocations of membrane. One is cross flow type MBR of which module is located outside of the bioreactor and mixed liquor is driven into the membrane module. The other is submerged type MBR process of which module is submerged in the bioreactor and mixed liquor is generally sucked from the lumen side. addition to that the cake layer is often removed by the uplifting flow of bubbling air. A submerged MBR process is superior to a crossflow MBR in regard to the power consumption because suction pressure of a submerged MBR is generally lower than that of a crossflow MBR which has recirculation pump. A submerged MBR, therefore, has the potential to be applied to small wastewater treatment plants that need low cost treatment systems.

• Membrane Journal
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• v.11 no.4
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• pp.170-178
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• 2001

PVC microfiltration membrane was prepared by phase immersion method and applied to membrane bioreactor (MBR) contained activated sludge. The hydrophilicity of membrane and the pore size increase with the amount of additive(PVP) ducting the preparation of membrane. Permeation characteristics and the membrane fouling behavior were investigated by varying the internal environment in MBR using the prepared membranes. When there is a sludge bulking in MBR caused by microorganism, membrane fouling was accumulated. The cake layer resistance, R$_{c}$, of membrane increased in the order of CP-0 > CP-1.0 > CP-1.5. Rc increased up to 3.5~7 fold where the sludge bulking occurred in MBR. CP-1.5 seems to be appropriated membrane on the basis of the surface characteristics and the flux. The average flux of all the test membrane was 12(${\pm}$2) L/$m^2$hr whereas the COD removal efficiency was 98.8%. The ratio of bulking sludge and the type and the size of microorganism in operating MBR accelerate the membrane fouling and flux decline. It is concluded that the characteristic of membrane filtration depends on the hydrophilicity of membrane, the internal environment of MBR reactor and the growth factor of sludge.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.521-526
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• 2006

A membrane bioreactor (MBR) is an effective tool for wastewater treatment with recycling. MBR process has several advantages over conventional activated sludge process (ASP); reliability, compactness, and quality of treated water. The resulting high-quality and disinfected effluents suggest that MBR process can be suitable for the reused and recycling of wastewater. An anoxic/oxic (A/O) type MBR was applied to simultaneous removal of organics and nutrients in sewage. At first, the efficiency of submerged MBR process was investigated using a hollow fiber microfiltration membrane with a constant flux of $10.2L/m^2{\cdot}h$ at each solids retention time (SRT). Results showed that protein/carbohydrate (P/C) ratio increased and total extracellular polymeric substances (EPS) remained constant with SRT increased. Secondly, A/O type MBR with a reverse osmosis (RO) membrane was employed to treat the municipal wastewater. The performance of A/O type MBR-RO process is better for the treatment of organics and nutrients than ASP-MF-RO process in terms of consistent effluents quality.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.1
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• pp.31-36
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• 2008

This work was performed to evaluate the effect of membrane material and structure on fouling in a submerged membrane bioreactor(MBR). Three types of microfiltration membranes with the same pore size of 0.1 $\mu$m but different materials, polytetrafluoroethylene (PTFE), polycarbonate(PCTE) and polyester(PETE), were used. While PETE membrane exhibited the most rapid flux decline throughout the operation, PCTE and PTFE had a similar tendency with regard to permeability. Difference in permeability between PETE and the other membranes gradually decreased with time, which was probably due to chemical cleaning. The higher TOC rejection of PETE membrane could be attributable to its faster fouling, resulting from a larger amount of foulants to get attached to the membrane in a shorter time. DOC fractionation using a DAX-8 resin showed that the composition of each fraction between the supernatant and permeates did not change significantly with operation time, indicating that membrane hydrophilicity/hydrophobicity was not a dominant factor affecting to MBR fouling in this study. Compared to other membranes, the fouling of PETE membrane was more influenced by pore clogging (irreversible fouling), which would probably contribute to a higher organic rejection of the PETE membrane.

• Membrane Journal
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• v.15 no.3
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• pp.241-246
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• 2005

This study is investigated for the applications of MBR SYSTEM using $ENVIS^{(R)}$ which is a submerged flat membrane for treatment of sewage and wast water. The experiment was practiced on the scene of labor that are sewage facilities of factories $(10\;m^3/day)$ and wast water treatment plant $(30\;m^3/day)$ using equipments made by Pure-Envitech Co., LTD. SS, BOD and COD for the result of removal efficiency at the sewage facilities of factories were $99.7\%,\;97.6\%$, and $96.8\%$, rspectively. SS, BOD and COD for the result of removal efficiency at the waste water treatment plant were $99.6\%,\;95.6\%,\;and\;80.3\%$, respectively.

• Membrane Journal
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• v.20 no.2
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• pp.127-134
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• 2010

This study is conducted about the system that reduces organism after fermenting food waste from a food waste disposal equipment, divides gas made when food waste is fermented into gas and water, and then sends gas to a reactor again, condenses water, and apply it to the MBR system with submerged MF hollow fiber membranes. A submerged MF hollow fiber membrane module was installed to a food waste disposal equipment and a water treatment system made by Bio Hitech Co,. Ltd. to process food waste generated from a staff cafeteria in a H institute for 90 days. For initial seeding of a food waste disposal equipment, 305 kg of rice bran, chaff, and sawdust as well as 1,648 kg of food were input during the operation, and 1,600 L of condensed wastewater occurred. Fermented by-product after finishing running a food waste disposal equipment was 386 kg and its reduction was shown to be 80%. The organism was processed by applying submerged MF hollow fiber membrane module to the MBR system of condensed wastewater, and the result shows reduction rates were BOD 99.9%, COD 97.5%, SS 98.6%, T-N 54.6% and T-P 34.7% and the total colon bacillus was perfectly eliminated.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.383-390
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• 2011

In this study, a process combined biofiltration with sulfur-utilizing autotrophic denitrification and membrane separation was proposed to examine the efficiency of nitrogen removal. As an experimental device, hollow-fiber module was installed in the center of reactor to generate the flux forward sulfur layer in the cylinder packed with granular sulfur. In addition, a simple module was installed in activated sludge aeration tank which inside and outside of sulfur-using denitrification module was covered with microfilter and the module was considered as an alternative of clarifier. The experiment for developing new MBR process was carried out for three years totally. As the results of first two-year experiment, successful nitrogen removal performance was revealed with lab-scale test and pliot scale plant using artificial wastewater and actual plating wastewater. In this year, pilot scale test using actual domestic wastewater was performed to prove field applicability. As the results, high-rate nitrogen removal performance was confirmed with about 0.19 kg ${NO_3}^--N/m^3$ day of rate. Also significant fouling and pressure increase were not found during the experiment. And, the production ratio of sulfate and the consumption ratio of alkalinity showed a slightly higher value about 311 mg ${SO_4}^{2-}/L$ and 369 mg $CaCO_3$/L, respectively. In conclusion, the developed MBR process can be utilized as an alternative for retrofiting existing wastewater plants as well as new construction of advanced sewage wastewater treatment plants, with cost-effective merit.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.200-208
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• 2005

In this study, a new submerged membrane bioreactor process packed with granular sulfur (MBR-GS) was operated to identify the biological nitrogen removal behaviors with plating wastewater containing high-strength $NO_3{^-}$ concentration. The continuous denitrification was carried out at $20^{\circ}C$ with various nitrogen loading rates using synthetic wastewater, which composed of $NO_3{^-}$ and $HCO_3{^-}$, but also actual plating wastewater, which was collected from the effluent of the H metal plating company. As a result, high-rate denitrification in the range of $0.8kg\;NO_3{^-}-N/m^3\;day$ was accomplished at nitrogen loading rate of $0.9kg\;NO_3{^-}-N/m^3\;day$ using synthetic wastewater. Also, higher-rate denitrification with actual plating wastewater was achieved up to $0.91kg\;NO_3{^-}-N/m^3\;day$ at the loading rate of $1.11kg\;NO_3{^-}-N/m^3\;day$. Additionally, continuous filtration was possible during up to 30 days without chemical cleaning in the range of 20 cmHg of transmembrane pressure. On the basis of the proposed stoichiometry, ${SO_4}^{2-}$ production could be estimated efficiently, while observed alkalinity consumption was somewhat lower than theoretical value. Consequently, a new process, MBR-GS is capable of high-rate autotrophic denitrification by compulsive flux and expected to be utilized as an alternative of renovation techniques for nitrogen removal from not only plating wastewater but also municipal wastewater with low C/N ratio.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.323-328
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• 2016

Pressurized membrane used for side-stream MBR process requires fouling control strategy both for normal and abnormal operation conditions for stable operation of the facilities. In this study, $85m^3/day$ of pilot-scale side-stream MBR process was constructed for the evaluation of fouling mitigation by air bubble injection into the membrane module. In addition, fouling phenomena at abnormal operation conditions of low influent and/or loading rate were also investigated. Injection of air bubble was found to be effective in delaying transmembrane pressure (TMP) increase mainly due to scouring effect on the membrane surface, resulting in expanded filtration cycle at a high flux of $40L/m^2{\cdot}h$ (LMH). At abnormal operation condition, injection of PACl (53 mg/L as Al) into the bioreactor showed 19% reduction of TMP increase. However, inhibition of nitrifying bacteria by continuous PACl injection was observed from batch experiments. In contrast, injection of powdered activated carbon (PAC, 0.6 g/L) was able to maintain the initial TMP of $0.2kg/cm^2$ for 5 days at the abnormal conditions. It may have been caused from the adsorption of extracellular polymeric substances (EPS), which was known to be excessively released during growth inhibition condition and act as the major foulants in MBR operations.

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.257-264
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• 2006

An aerobic submerged membrane bioreactor (MBR) treating ammonium wastewater was studied in respect of nitrification characteristics and distribution of nitrification bacteria over a period of 350 days. MBR was fed with ammonium concentration of 500-1000 mg $NH_4-N/L$ at a nitrogen load of $1-2kg\;N/m^3{\cdot}d$. Overall ammonium oxidation rate increased with dissolved oxygen (DO) concentration, temperature, and sludge retention time (SRT). Under a higher concentration of free ammonia ($NH_3-N$) due to the decrease of ammonium oxidation rate, the nitrite ratio ($NO_2-N/NO_x-N$) in the effluent increased. The sudden collapse of nitrification efficiency accompanied by sludge foaming and the increase of sludge volume index (SVI) was observed unexpectedly during the operation. At the later stage of operation, additional carbon source was fed to the MBR and resulted in twice higher value of SVI and the decrease of ammonium oxidation rate. In fluorescence in situ hybridization (FISH) analysis, genus Nitrosomonas which is specifically hybridized with probe NSM156 was initially the dominant ammonia oxidizing bacteria and the amount of Nitrosospira gradually increased. Nitrospira was the dominant nitrite oxidizing bacteria during whole operational period. Significant amount of Nitrobacter was also detected which might due to the high concentration of nitrite maintained in the reactor.