• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.95-96
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• 1999

The ultrafiltration behavior of dilute colloidal solution containing Si particles has been investigated. The experiments in cross flow mode have been performed at different operating condition by using the membrane with 20 kDa cut-off. The flux decline was due to the development of membrane fouling which was a dynamic process of two distinctive stages. For the high trans-membrane pressure, the pore blocking resistance was dominant at the initial period of filtraion and was followed by the cake resistance. And for the low cross flow velocity, the membrane fouling was governed by the cake filtration model at the initial stage of filtration process. Flux jump was observed temporally during the membrane filtration of mixed feed solution.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.3
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• pp.281-288
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• 2008

Cake resistance is influenced by floc size deposited on membrane surface. Enlarging floc size can reduce cake resistance. The small particles are enlarged by coagulation and flocculation process in conventional mixing tank at membrane filtration system. Fully-grown flocs for reducing the cake resistance, however, are ruptured while passing through a pump. In light of this fact, this study aims to experimentally look at the reaggregation phenomenon of mixing system. In addition, reaggregation phenomenon of mixing system is compared with first-aggregation of in-line injection system in which coagulant is injected just before a pump. These results suggest that first-aggregation of in-line injection system is better than reaggregation of mixing system for G-value above $3100sec^{-1}$. Since G-value in pipe of actual membrane filtration system are usually larger than $3100sec^{-1}$. The performance of in-line injection system is expected to be better than the conventional mixing tank system.

• Membrane and Water Treatment
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• v.4 no.3
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• pp.175-189
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• 2013

A membrane bioreactor (MBR) with sludge retention time (SRT) of 300 days was maintained for over 2 years. Polypropylene microfiltration (MF) membrane with pore size of 0.2 ${\mu}m$ was used in the MBR system. The fouling behaviors of various sludge fractions from the MBR were studied and sub-divided resistances were analyzed. It was observed that $R_{cp}$ was a dominant resistance during the filtration of activated sludge, contributing 63.0% and 59.6% to the total resistance for MBR and sequential batch reactor (SBR) respectively. On the other hand, $R_c$ played the significant role during the filtration of supernatant and solutes, varying between 54.54% and 67.18%. Compared with $R_{cp}$ and $R_c$, $R_{if}$ was negligible, and $R_m$ values remained constant at $0.20{\times}10^{12}m^{-1}$. Furthermore, resistances of all sludge fractions increased linearly with rising mixed liquor suspended solids (MLSS) concentration and growing trans-membrane pressure (TMP), while the relationship was inversed between fraction resistances and cross flow velocity (CFV). Among all fractions of activated sludge, suspended solid was the main contributor to the total resistance. A compact cake layer was clearly observed according to the field emission scanning electro microscopy (FE-SEM) images.

• Membrane Journal
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• v.23 no.6
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• pp.439-449
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• 2013

This study investigated the aromatic polyamide reverse osmosis membrane was modified with diphenylamine (DPA) for enhanced chlorine and fouling resistance and how to optimize. DPA has high reactivity and thermo chemical stability. The performance of a modified membranes was investigated and its surface analyzed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The experiment was conducted while changing the conditions of temperature and DPA solution concentration.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.17-22
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• 2006

This study is about backwash condition and membrane fouling at continuous coagulation/ultrafiltration process in water treatment. The capacity of pilot plant was $0.06m^3/d$. The result of the test, Backwash cycle time and duration time had a significant effect on the efficiency of system and backwash. Backwash duration time was determined to be fixed in 30 seconds for the system with more than 95% recovery rate, It needed 30 minute backwash frequency. During the continuous operation, membrane fouling was analyzed by determining the filtration resistance ($R_i$) and cake layer resistance ($R_c$). At the initial stage, filtration resistance highly influenced the fouling behavior. But after 1.5 hours, cake layer resistance became more important than filtration resistant.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.141-148
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• 2009

The purpose of this paper is to propose a standard test methods of resistance to root penetration for waterproofing and rootproofing membrane using green roof system. Green roof system is considered to be an important subject in construction industry for green growth project. At the same time, we have to consider the counterplan for protection the damage of waterproofing layer and concrete substrate from the penetration of plant root. But many kinds of materials for protection from root penetration are using in construction field. But the performance of those materials is not clear, and there is not test methods for the evaluation of performance. So in this paper, based on the research results of 4 institutes during four years and foreign cases, we made a standard test methods of resistance to root penetration for waterproofing and rootproofing membrane using green roof system. This test method deals with about environmental condition of laboratory, experimental facilities, kinds of plant, specimen of test, management methods, evaluation duration and documents, etc.

• Computers and Concrete
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• v.31 no.6
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• pp.469-484
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• 2023

The response mechanism of simply supported two-way reinforced concrete (RC) slabs under fire was numerically studied from the view of stress redistribution using the finite element software ABAQUS. Results show that: (1) Simply supported two-way RC slabs undergo intense stress redistribution, and their responses show four stages, namely elastic, elastic-plastic, plastic and tensile membrane stages. There is no cracking in the fire area of the slabs until the tensile membrane stage. (2) The inverted arch effect and tensile membrane effect improve the fire resistance of the two-way slabs. When the deflection is L/20, the slab is in an inverted arch effect state, and the slab still has a good deflection reserve. The deformation rate of the slab in the tensile membrane stage is smaller than that in the elastic-plastic and plastic stages. (3) Fire resistance of square slabs is better than that of rectangular slabs. Besides, increasing the reinforcement ratio or slab thickness improves the fire resistance of the slabs. However, an increase of cover thickness has little effect on the fire resistance of two-way slabs. (4) Compared with one-way slabs, the time for two-way slabs to enter the plastic and tensile cracking stage is postponed, and the deformation rate in the plastic and tensile cracking stage is also slowed down. (5) The simply supported two-way RC slabs can satisfy with the requirements of a class I fire resistance rating of 90 min without additional fire protection.

• Membrane Journal
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• v.30 no.2
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• pp.138-148
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• 2020

The purpose of this study was to identify the cleaning efficiency of fouled multi-bore hollow fiber membranes after purification of contaminated water. The PSf (polysulfone) based hollow fiber membrane manufactured by Pure & B Tech Co., Ltd. Was used in this study. The antifouling characteristics during the water treatment were studied using bovine serum albumin (BSA) as a model compound and the chemical resistance was evaluated after long-term impregnation in sodium hypochlorite (NaOCl) solution and Citric acid to understand the long term stability of the membranes. Water permeability and mechanical strength of the membranes after prolonged chemical exposure was measured to observe the change in mechanical stability and long term performance of the membrane. moreover, the recovery efficiency was also evaluated after chemical enhanced backwashing of a membrane contaminated with bovine serum albumin. The PSf hollow fiber membrane exhibited excellent chemical resistance, and it was confirmed that the efficiency of sodium hypochlorite was high as a result of chemical enhanced backwashing.

• Journal of Korean Society on Water Environment
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• v.21 no.4
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• pp.337-346
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• 2005

An MSBR using a membrane for not only filtration but also aeration (MA-MSBR) was designed to reduce membrane fouling and to enhance water quality, and compared with an MSBR using a membrane for only filtration (BA-MSBR). COD removal efficiency of the MA-MSBR was similar to that of the BA-MSBR, but membrane performance of the MA-MSBR was better than that of the BA-MSBR. The MA-MSBR had more small particles in mixed liquor, so the specific cake resistance of flocs in the MA-MSBR was higher than that in the BA-MSBR. However, in the aerobic reaction step of the MA-MSBR, air went through membrane pores and out of the membrane surface, so cake layers on the membrane surface and a portion of organics adsorbed on membrane pores could be removed periodically. Therefore, cake resistance, $R_c$, and fouling resistance by adsorption and blocking, $R_f$, for the MA-MSBR increased more slowly than those for the BA-MSBR. Additionally, in order to compare the energy efficiency for two MSBRs, oxygen transfer efficiency and power to supply air into the reactor by a membrane module and a bubble stone diffuser were measured using deionized water. From these measurements, the transferred oxygen amount per unit energy was calculated, resulting that of MA-MSBR was slightly higher than that of BA-MSBR.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.171-175
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• 2020

In the proton exchange membrane fuel cells (PEMFC), the development of a reinforced membrane with improved durability by a support is actively in progress in Korea. In this study, the initial performance and characteristics of four types of reinforced membranes were compared. Reinforced membranes with higher amounts of C-F chains in the polymer membrane showed lower water diffusion coefficients due to the hydrophobicity of the C-F chains. The thicker the polymer membrane, the more the hydrogen permeability decreased and the higher the OCV. Membrane with short resistance below 1.5 Ωcm² showed OCV below 0.9 V and the lowest performance, so short resistance should be above 3.0 Ωcm². Compared with the current standard membrane, there was a similar domestic membrane, which could confirm the possibility of localization of PEMFC polymer membrane.