• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.629-637
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• 2000

A two-phase anaerobic reactor with a submerged microfiltration system was tested for its ability to produce methane energy from organic wastewater. A membrane separation system with periodic backwashing with compressed air was submerged in the acidogenic reactor. The cartridge type of microfiltration (MF) membrane with pore size of $0.5{\mu}m$ (mixed esters of cellulose) was tested. An AUBF (Anaerobic Upflow Sludge Bed Filter: 1/2 packed with plastic media) was used for the methanogenic reactor. Soluble starch was used as a substrate. The COD removal was investigated for various organic loading with synthetic wastewater of 5,000 mg starch/L. When the hydraulic retention time (HRT) of the acidogenic reactor was changed from 10 to 4.5 days, the organic loading rate (OLR) varied from 0.5 to $1.0kg\;COD/m^3-day$. When the HRT of the methanogenic reactor was changed from 2.8 to 0.5 days, the OLR varied from 0.8 to $5.8kg\;COD/m^3-day$. The acid conversion rate of the acidogenic reactor was over 80% in the 4~5 days of HRT. The overall COD removal efficiency of the methanogenic reactor showed over 95% (effluent COD was below 300 mg/L) under the highly fluctuating organic loading condition. A two-phase anaerobic reactor showed an excellent acid conversion rate from organic wastewater due to the higher biomass concentration than the conventional system. A methanogenic reactor combined with sludge bed and filter, showed an efficient COD and SS removal.

• Membrane Journal
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• v.27 no.3
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• pp.263-272
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• 2017

There are several different methods to characterize membrane pore size distribution, however, it is yet difficult to accurately measure pore size range of 10-50 nm. In this work, we employed gas-liquid displacement porometer (GLDP) and liquid-liquid displacement porometer (LLDP) to characterize in-house alumina hollow fiber membrane (K-100) and commercial membranes (A-100, A-20) that exhibit pore sizes between 10-100 nm. GLDP method was more suitable for measuring the maximum pore size, and the measured mean pore size of the membranes by LLDP were better correlated with water permeability and solute rejection. It was determined that LLDP is effective for measuring pore sizes between 10-50 nm; however, the method holds intrinsic disadvantages such as low precision and high sensitivity compared to that of GLDP. Nevertheless, it is expected that the recently commercialized LLDP technique can provide useful data that other methods cannot.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.491-498
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• 2005

J sewage treatment plant (WWTP) in Busan has used methanol as an external carbon source for the biological denitrification process. Methanol is widely used. but rather expensive and very dangerous in handling. Therefore, it has been required that the economic alternative carbon source must be developed. By-product from a fine chemical industry can be Purified by removing high molecular weight substances using the ultrafilter membrane separation process and RBDCOD fraction becomes $98{\sim}99%$ of COD substances in the purified by-product. The purified by-product containing three types of alcohols, methanol, prophylenglycol and methoxypropanol; showed similar chemical characteristics to the methanol, a main external carbon source, in biodegradation pathway. Shown above, the compatibility between main and alternative carbon sources has been achieved. Also very short or no adaptation period is necessary in the case of exchanging these carbon sources. The compatibility between external carbon sources is an essential element for stabilizing WWTP operations. During the full-scale application test of the by-product, the alternative carbon source line got on par with the treatment efficiency of the methanol line. With the test result, J-WWTP changed methanol to a fine chemical by-product, in two out of three J-WWTP lines. Moreover, it is expected that 55.4% of the external carbon source cost reduction can be achieved in the alternative carbon source applied lines.

• Membrane Journal
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• v.19 no.1
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• pp.34-46
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• 2009

Effect of backflushing on the membrane fouling for polyethylene capillary membranes was examined by measuring the flux of $Al_2O_3$ colloidal suspensions through the cross flow microfiltration. In the comparison of with and without the application of backflushing, the hydraulic resistance to permeate flow of the suspension was less with backfluslng, but the Increasing rate in permeate resistance was higher. Regardless of backflushing, the cake filtration was dominant at the initial period of filtration with backflushing, being followed by the pore blocking. And at steady state, the fouling mechanism is almost governed by the cake filtration model. On the contrary, the pore blocking preceded the cake filtration in the initial stage of the original membrane before backflushing. And irrespective of backflushing, the ratio of cake filtration to total fouling increased, compared with that fur before backflushing. For the membrane with $0.24{\mu}m$ pore size, the permeate resistance was higher than that of $0.34{\mu}m$ pore size membrane. but the ratio of cake filtration was smaller than that of large pore membrane. In comparing the ratio of each fouling component to the total fouling for the case with backflushing pore blocking was 7.8% and cake filtration was 92.2%. for the case without backflushing, total fouling was composed of 9.6% pore blocking and 90.4% cake filtration.

• Membrane Journal
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• v.19 no.1
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• pp.7-18
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• 2009

In this study, we used the hybrid module that was composed of granular activated carbons (GAC) packing between module inside and outside of tubular ceramic microfiltration membrane for advanced drinking water treatment. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, modified solution was prepared with humic acid and kaolin. We were investigated effect of water-back-flushing time (BT) and water-back-flushing period (FT) to minimize membrane fouling and to enhance permeate flux (J) in the hybrid process, and tried to find the optimal operating conditions. As a result, resistance of membrane fouling ($R_f$) was slightly decreased according to increasing BT. Also, the shorter FT was the more effective to reduce $R_f$ and to enhance J because of frequent water-back-flushing. However, the optimal BT and FT conditions were 10 sec and 8 min respectively when operating costs were considered. Then, the optimal conditions derived from our experiments of modified solution were applied to lake water treatment. As a result, average treatment efficiencies of turbidity, $UV_{254}$ absorbance, and $COD_{Mn}$ were very high as 99.11%, 91.40% and 89.34%, respectively, but that of TDS was low as 30.05%.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.559-569
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• 2007

The purposes of this study were to find the main foulant of membrane and the optimal chemical cleaning method for MF(microfiltration) drinking water treatment system using D dam water as water source. The MF pilot plant which can treat maximum $500m^3/d$ consisted of 3 racks and was operated for 10 months under various operation conditions. After 10 months operation, $1^{st}$ and $2^{nd}$ rack of membrane pilot plant system were cleaned chemically and the degree of the restoration of the fouled membrane in terms of the pure water flux was detemnined. Inorganic compounds which contained in chemical cleaning waste was analyzed by Inductively Coupled Plasma (ICP). One membrane module for 3rd rack was disjointed and membrane fouling materials, especially inorganic compounds were investigated by Electron Probe Microanlysis (EPMA) to elucidate the reason of TMP increase. And also, the various chemical reagents (1N HCl or $H_2SO_4$, oxalic acid as acid and 0.3% NaOCl as alkali) were tested by combination of acid and alkali to determine the optimal chemical cleaning method for the MF system using micro-modules manufactured using the disjointed module. It was verified that the inside and outside of membrane module was colorized with black. As a result of the quantitative and semi-qualitative analysis of membrane foulant by ICP, most of inorganic foulant was manganese which is hard to remove by inorganic acid such as HCI. Especially, it was observed by EPMA that Mn was attached more seriously in inside surface of membrane than in outside surface of that. It was supposed that Mn fouling in inside surface of membrane might be caused by the oxidation of soluble manganese (Mn(II)) to insoluble manganese ($MnO_2$) by chlorine containing in backwashing water. The optimal cleaning method for the removal of manganese fouling was consecutive cleaning with the mixture of 1N HCl and 1% of oxalic acid, 0.3% NaOCl, and 1N HCl showing 91% of the restoration of the fouled membrane.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.190-194
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• 2009

In this study sodium dodecyl sulfate (SDS), which was anionic surfactant, was added for forming micelles to remove iron ion that could be contained with small amount in industrial water. Then aggregates binding between iron ions and micelles were rejected by a ceramic microfiltration membrane. As result of SDS concentration effect on removal rates of iron and SDS in modified iron solution, the removal rate of iron was the highest value of 92.26% and the removal rate of SDS was 61.10% a little higher than the result of calcium ion at 8 mM which was CMC (Critical micelle concentration) of SDS. As final resistance of membrane fouling $R_f$ increased the more at the higher SDS concentration, it showed the highest value at 4 mM and the lowest at 10 mM of SDS. The final permeate flux $J_{180}$ had the highest value and the largest total permeate volume could be finally acquired at SDS 10 mM. In case of CMC 8 mM, low $R_f$ was shown as same as that of 10 mM until 80 minutes of operation, and tended to increase dramatically to 120 minutes and increase slowly again until 180 minutes.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.624-629
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• 2013

The relation between performance maintenance conditions and those cost efficiency was studied to choose an optimum operating condition in the seawater desalination pretreatment system. A hollow fiber microfiltration module, which was developed with domestic technology, was tested with the various operating conditions such as chemically enhanced backwash cycles and design dosages of a cleaning chemical. Transmembrane pressure was measured to investigate membrane fouling status and cleaning degree. In addition, economic analysis was performed to compare water production costs by the operation condition. As a result, The operation mode III, chemically enhanced backwash at once a day with 100 mg/L of sodium hypochlorite (NaOCl) was selected. The concurrent evaluation between membrane filtration performance and its economic analysis will be suitable to choose an efficient optimum condition.

• Membrane Journal
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• v.18 no.3
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• pp.191-197
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• 2008

In this study, we used hybrid module that was composed of packing granular activated carbon (GAC) between module inside and outside of ceramic microfiltration membrane for advanced drinking water treatment. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, synthetic water was prepared with humic acid and kaolin. Packing fraction of GAC was changed from 0 to 24.05% to see effect of packing fraction. As a result, changing curves of resistance of membrane fouling ($R_f$) and permeate flux (J) during 3 h operation were almost overlapped independent of packing fraction of GAC. Treatment efficiencies of turbidity were very high above 99.46% at all packing fractions of GAC. And treatment efficiency of NOM, which was measured by $UV_{254}$ absorbance, was the highest value of 99.43% at packing fraction of 24.05%. Then, we operated the hybrid process during 13 h at packing fraction of 24.05%. As a result, J was rapidly dropped according to increase of membrane fouling within initial 1 h of operation, and almost constant after 3 h. And treatment efficiencies of turbidity and NOM were stable and high values of 99.52% and 96.63%, respectively.

• Membrane Journal
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• v.21 no.1
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• pp.72-83
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• 2011

For advanced drinking water treatment of high turbidity water, we used the hybrid module that was composed of photocatalyst packing between outside of tubular ceramic microfiltration membrane and membrane module inside. Photocatalyst was PP (polypropylene) bead coated $TiO_2$ powder by CVD (chemical vapor deposition) process. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, modified solution was prepared with humic acid and kaolin. Water-back-flushing of 10 sec was performed per every period of 10 min to minimize membrane fouling. Resistance of membrane fouling ($R_f$) decreased and J increased as concentration of humic acid changed from 10 mg/L to 2 mg/L, and finally the highest total permeate volume ($V_T$) could be obtained at 2 mg/L. Then, treatment efficiencies of turbidity and $UV_{254}$ absorbance were above 98.5% and 85.7%, respectively. As results of treatment portions by membrane filtration, photocatalyst adsorption, and photo-oxidation in MF, MF + $TiO_2$, and MF + $TiO_2$ + UV processes, turbidity was treated little by photocatalyst adsorption, and photo-oxidation. However, treatment portions of humic acid by adsorption and photo-oxidation were above 10.7 and 8.6%, respectively.