• Title/Summary/Keyword: 막오염물질

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Effects of various foulants on flux changes in membrane distillation process (막증류 공정에서 오염 인자가 플럭스 변화에 미치는 영향)

  • Park, Chansoo;Lee, Chang-Kyu;Kim, Jong-oh;Choi, June-Seok
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.3
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    • pp.327-334
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    • 2016
  • The effects of dissolved inorganic and organic matter in seawater and the characteristics of fouling on the membrane surface were investigated within membrane distillation (MD) process. The changes of the membrane flux of PE and PVDF hollow fiber membranes under natural and synthetic seawater were compared with given variances of temperature. The flux of both membranes under the synthetic seawater, without any organic matter, were higher than that of the natural seawater, indicating the organic fouling on the membrane surface. The surface of the membrane was analyzed using scanning electron microscope (SEM) to examine the fouling. The experiment with organics has shown the formation of thin film over the membrane surface, while the experiment with inorganics has shown only the formation of inorganic crystals. The results indicated the organic matter as the major foulants and that the organics affected the formation of the crystals. Permeate water conductivity of all conditions verified the quality of the water to be better if not similar to that of RO.

Particle and NOM Fouling in Ultrafiltration with Softening Pretreatment (연수화 전처리를 적용한 한외여과에서 입자상 물질 및 자연유기물 막오염)

  • Kweon, Ji-Hyang;Lawler, Desmond F.
    • Journal of Korean Society of Water and Wastewater
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    • v.17 no.4
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    • pp.534-541
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    • 2003
  • Membrane processes are now frequently considered for application in drinking water treatment. The biggest impediment for applying membrane processes is fouling that comes from mass flux (such as particle and organic matter) to the membrane surface and its pores due to convection flow through the membrane. Natural organic matter (NOM) has been reported as the most detrimental foulant. Some research also indicated that particles were often the dominant cause of fouling. Therefore, both NOM and particle fouling need to be examined to better understand fouling in ultrafiltration. Two waters from natural sources, Lake Austin water and Missouri River water, were selected. Both waters are relatively hard waters but has significantly different particle concentrations, which will elucidate effects of particles on membrane fouling. Precipitative softening is traditionally designed to remove hardness ions in hard waters but it can also remove particles and organic matter. Therefore, the integrated water treatment with softening and ultrafiltration is proposed as a promising option for hard waters. The three levels of softening were used to represent different degrees of pretreatment to ultrafiltration in terms of organic matter (i.e., NOM fouling) and precipitates (i.e., particle fouling by further precipitation). Results showed that natural particles in Missouri River water was detrimental foulants of ultrafiltration. As the levels of softening were increased, NOM and particle removal was increased, and thus fouling was decreased. Direct images of the surface of the membranes by scanning electron microscopy allowed observation of the different properties of particles caught in fibril networks of natural organic matter.

Effect of Trans-Membrane Pressure on Reversible and Irreversible Fouling Formation of Ceramic Membrane (막간차압이 세라믹막의 가역막오염과 비가역막오염 형성에 미치는 영향)

  • Lee, Heewon;An, Kwangho;Choi, Juneseok;Kim, Seogku;Oh, Hyunje
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.9
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    • pp.637-643
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    • 2012
  • This study was carried out to investigate how reversible and irreversible fouling were distributed in the filtration using ceramic membrane of 300 kDa pore size for secondary effluent of wastewater. It was performed by calculating fouling as numerical method for diverse TMPs and measured F-EEM and SEC for raw water, treated water and backwashed water. Water quality was also checked to know whether treated water quality was stable or not. The results showed that reversible fouling formation was increased when lower TMP was applied and it is caused by protein like organic matters having higher molecular weights. The secondary wastewater effluent had diverse molecular weight materials, especially contaminants lower than 0.5 kDa and bigger than 12 kDa. Decreasing TMP induced contaminants above 12 kDa and below 1 kDa to become reversible fouling.

A study on mitigation of membrane fouling by ozonation/coagulation in ultrafiltration (오존산화/응집 혼성공정에 의한 UF 분리막의 막오염 저감에 관한 연구)

  • Kim, Geon-Youb;Kim, Min-Gue;Lee, Chang-Ha;Kim, Hyung-Soo;Kim, Ji-Hoon;Lee, Kyung-Il
    • Journal of Korean Society of Water and Wastewater
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    • v.31 no.2
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    • pp.161-168
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    • 2017
  • Microfiltration (MF) and Ultrafiltration (UF) membrane processes capable of producing highly purified water have been extensively applied as a pretreatment process in the wastewater reuse field with the improvement of membrane properties and resistance, development of operating protocols, and improvement of technologies of backwashing and physicochemical cleaning, and improvement of scale and antifoulants. However, despite of the development of membrane production and process technologies, fouling still remains unresolved. This study confirmed that foulants such as polysaccharides, proteins and humic substances existed in final treated effluent (secondary effluent) by fluorescence excitation emission matrix (FEEM) and fourier transform infrared spectroscopy (FTIR) analysis. In addition, when constructing ozone oxidation and coagulation processes as a hybrid process, the removal efficiency was 5.8%, 6.9%, 5.9%, and 28.2% higher than that of the single process using coagulation in turbidity, color, dissolved organic carbon (DOC), and UV254, respectively. The reversible and irreversible resistances in applying the hybrid process consisting of ozone oxidation and coagulation processes were lower than those in applying ozone oxidation and coagulation processes separately in UF membrane process. Therefore, it is considered possible to apply ozonation/coagulation as a pretreatment process for stable wastewater reuse by and then contributing to the reduction of fouling when calculating the optimal conditions for ozone oxidation and coagulation and then to applying them to membrane processes.

Effect of Coagulation in Coagulation/Ultrafiltration Hybrid System in Water Treatment Process (정수처리용 응집.한외여과 혼성공정에서 응집 효과에 관한 연구)

  • Moon, Seong-Yong;Lee, Sang-Hyub;Kim, Seung-Hyun;Yoon, Cho-Hee
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.8
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    • pp.837-843
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    • 2005
  • Coagulation influence was evaluated as the pretreatment for ultrafiltration. Coagulation was expected to improve water quality, reduce membrane fouling and increase backwash effect. Continuous operation of UF was employed in order to investigate the influence of coagulation. Alum, PACS and Ferric chloride were used as coagulants separately. From the result of the research, coagulation can improve the treated water quality greatly. Organic removal was increased more than turbidity and showed an improvement of 30.6% at most. All three coagulants presented conspicuous reduction of membrane fouling, among which PACS was the most effective with long term run. Backwash effect differed with different coagulants while Ferric chloride turned out to be the most effective one. The optimum dosage of coagulant resulted in the highest backwash efficiency.

Effect of Water-back-flushing in Advanced Water Treatment System by Tubular Alumina Ceramic Ultrafiltration Membrane (관형 알루미나 세라믹 한외여과막에 의한 고도정수처리 시스템에서 물 역세척의 영향)

  • Park, Jin-Yong;Lee, Song-Hui
    • Membrane Journal
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    • v.19 no.3
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    • pp.194-202
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    • 2009
  • In this study periodic water-back-flushing using permeate water was performed to minimize membrane fouling and to enhance permeate flux in advanced water treatment by tubular ceramic ultrafiltration membrane for Gongji stream in Chuncheon city. The back-flushing period (FT, filtration time) 2 min with periodic water-back-flushing of 15 sec showed the highest value of dimensionless permeate flux (permeate flux vs. initial permeate flux), and the lowest value of resistance of membrane fouling. Also in the results of BT effect at fixed FT 10 min, BT (back-flushing time) 20 sec showed the lowest value of resistance of membrane fouling and the highest value of dimensionless permeate flux, and we could be obtained the highest total permeate volume of 107.3 L. Consequently FT 10 min and BT 20 sec could be the optimal condition in Gongji stream water treatment, which was the exactly same results of our previous tubular alumina microfiltration. Then the average rejection rates of pollutants by our tubular ceramic UF system were 97.0% for turbidity, 32.1 % for chemical oxygen demand by manganese method, 28.8% for ammoniac nitrogen and 54.4% for T-P.

Application of electro-coagulation for the pretreatment of membrane separation of anaerobic digestion effluents (혐기성 소화액의 막분리를 위한 전기응집 전처리 연구)

  • Kim, Shin-Young;Chang, In-Soung;Kim, Jang-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.7
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    • pp.4665-4674
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    • 2014
  • The aim of this study was to confirm the feasibility of the electro-coagulation process as a pre-treatment for the membrane separation of anaerobic digestion effluents to minimize membrane fouling. The reduction of membrane fouling was evaluated according to the number of electrodes (immersed surface area of electrodes), current density and contact time. In the case of the small surface area of electrodes, the increased electric field strength resulted in a soluble COD increase due to the destruction of the microbial flocs and/or cells, whereas large changes in the soluble COD were not observed in the case of the high surface area of electrodes. On the other hand, the T-P concentration decreased as a result of the precipitation of aluminum ions and phosphates. The membrane permeation flux increased and the fouling resistance (Rc+Rf) decreased with increasing electric current density. Although the particle size of the anaerobic digestion effluent increased slightly, it was not related directly to the reduced fouling phenomena. The main mechanism for the enhanced flux was attributed to the inorganic particulate produced during electrocoagulation, such as $AlPO_4$, which acted as a dynamic membrane deposited on the membrane surface.

Effect of Membrane Materials on Membrane Fouling and Membrane Washing (막의 재질에 따른 막오염 특성 및 물리·화학적 세척의 영향)

  • Shim, Hyun-Sool;Jung, Chul-Woo;Son, Hee-Jong;Sohn, In-Shik
    • Korean Chemical Engineering Research
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    • v.45 no.5
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    • pp.500-505
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    • 2007
  • The objectives of this research were to (1) identify the membrane fouling potential due to different fractions of NOM (2) correlate the physicochemical properties of NOM and membranes with the adsorption of humic substances on membrane (4) find out the effect of membrane physical and chemical washing according to membrane material. The static adsorption test and adsorption test showed that hydrophobic organics adsorbed much more quickly than hydrophilic organics. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption rate ratio(a) of hydrophobic membrane (0.016, 0.077) was greater than that of hydrophilic membrane (0.010, 0.033) regardless of the kind of organic fractions. This suggests that the UF membrane fouling were occurred mainly by internal pore size decreasing due to adsorption of organic into pore surface for hydrophobic membrane, and by sieving of organics and forming a gel layer on the membrane surface for hydrophilic membrane. In conclusion, the decrease in the pore volume, which was caused by the organic adsorption into the internal pore, was greater with the hydrophobic membrane than with the hydrophilic membrane. In case of the effect of membrane properties on permeate flux, the rate of flux decline for the hydrophobic membrane was significantly greater than that for the hydrophilic membrane.

The Characterization of Floc Formation Under Various Pre-coagulation Conditions (응집-막분리 공정 적용시 전처리 응집조건에 따른 용존성 유기물 상(相)변화 특성)

  • Jung, Chul-Woo;Son, Hee-Jong
    • Journal of Korean Society of Environmental Engineers
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    • v.30 no.11
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    • pp.1139-1145
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    • 2008
  • The objectives of this research are to investigate the mechanism of coagulation affecting UF and find out the optimum conditions of the combined of coagulation with UF membrane filtration for NOM removal. During the mixing period, substantial changes in particle size distribution occurred under rapid and slow mixing condition due to the simultaneous formation of microflocs and NOM precipitates. Therefore, combined pretreatment using coagulation (both rapid mixing and slow mixing) improved dissolved removal efficiency. Also, for combined coagulation to membrane process, flux reduction rate showed lower than only UF process. The rate of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying coagulation process before membrane filtration showed not only reducing membrane fouling, but also improving the removal of dissolved organic materials that might otherwise not be removed by the membrane.

Characteristics of Permeation and Fouling of UF/MF Hollow Fiber Membranes for Drinking Water Treatment (정수처리 적용을 위한 UF/MF 중공사막의 투과성능과 오염현상)

  • 이주형;김정학;이용택
    • Membrane Journal
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    • v.10 no.2
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    • pp.75-82
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    • 2000
  • This study, which was tarried out to investigate the characteristics of permeation rates and fouling phenomena in drinking-water treating processes with MF membrane, showed that pressure drop was dependent on the length of membrane module and operating pressure; the pressure drop increased with the length of membrane module and operating pressure, operation at a relatively low pressure(0.5kg/$cm^2$) is better than that at a relatively (2.0kg/$cm^2$), since high operating pressure accelerates the clogging. In case of out-in permeation type, almost same flux was obtained after a certain operating time regardless of membrane length and operating pressure. In order to understand, the microbial fouling, chemical cleaning was carried out to the forced contaminated hollow-fiber membrane with chemicals($H_2O_2$, NaOCl, and NaOH). Chemical cleanings with $H_2O_2$and NaOCl, which are oxidizing agents, are better for sterilizing and desorbing the microbes than those with NaOH.

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