위 연구의 목적은 상용화 된 폴리아마이드 기반의 해수담수화 분리막 두 종류를 양쪽성 이온 화합물 중 하나인 MPC를 이용하여 표면 개질을 진행한 후, 내오염성 저감 평가에 대한 고찰이다. 표면 개시 원자 이동 라디칼 중합(SI-ATRP) 반응을 이용하여 표면 개질을 진행하였고, 개질 후 분리막 표면의 물리적, 화학적 특성들의 변화를 여러 분석 방법들을 이용해 분석해봄으로써 MPC가 분리막 표면에 합성이 되었음을 확인하였다. 또한 MPC가 개질 됨에 따라서 친수성이 증가한 표면으로 인하여 Sodium Alginate 와 Bovine Serum Albumin에 대한 두 차례의 내오염성 저감 평가 테스트를 통해서 개질 후 해수조건에서 분리막의 막 오염 현상이 저감 되었음을 확인하였다.
Membrane distillation (MD) is a thermally driven desalination process with a hydrophobic membrane. MD process has been known to have a lower fouling potential compared to other pressure-based membrane desalination process (NF, RO). However, membrane fouling also occurs in MD process. In this study, the membrane fouling was observed in MD process according to the pre-treatment processes. The filtration and precipitation processes were applied as the pre-treatment to prevent the membrane fouling. The pore sizes of roughing filters were 0.4, 5, 10, 30, and 60 ㎛. The concentration of the coagulant was 1.2 mg/L as FeCl3. The membrane fouling on MD membrane was successfully removed with both pre-treatment processes.
In this study, various physical cleaning methods such as physical washing and osmotic backwash, were conducted to understand membrane fouling properties by employing real secondary wastewater effluent (SWWE). In addition, microfiltration (MF) and ultrafiltration (UF) pretreatments were compared to maximize removal of organic matter and to control membrane fouling efficiently. Organic foulants deposited on the active layer of FO membrane were observed by fouling behavior test. The relationship between concentrations of natural organic matter and membrane fouling was also investigated from the bench-scale FO tests.
Growing demands for reducing energy consumption have raised interest to design advanced materials for thin film composite (TFC) desalination membranes with high permselectivity and low fouling. Here, we synthesized a star-shaped polymer as a new building block material, which can be assembled into selective layer of the TFC membrane via a facile interfacial polymerization (IP). Star polymer with compact globular structure and high density amine functional groups enabled to fabricate higher permselectivity and lower fouling propensity membrane compared to commercial membranes. In addition, star polymer assembled TFC membrane can function as either nanofiltration or reverse osmosis membrane by simply adjusting IP process conditions, which cannot feasible in conventional materials, demonstrating remarkable versatility of our star polymer.
In this study, the effects of operating conditions on the formation of reversible and irreversible fouling were investigated in the filtration using ceramic membrane for water treatment process. The effect of coagulation pretreatment on fouling formation was also evaluated by comparing the performance of membrane filtration both with and without addition of coagulant. A resistance-in-series-model was applied for the analysis of membrane fouling. Total resistance (RT) and internal fouling resistance (Rf) increased in the membrane filtration process without coagulation as membrane flux and feed water concentrations increased. Internal fouling resistance, which was not recovered by physical cleaning, was more than 70% of the total resistance at the range of the membrane flux more than 5 m3/m2・day. In the combined process with coagulation, the cake layer resistance (Rc) increased to about 30-80% of total resistance. As the cake layer formed by coagulation floc was easily removed by physical cleaning, the recovery rate by physical cleaning was 54~90%. It was confirmed from the results that the combined process was more efficient to recover the filtration performance by physical cleaning due to higher formation ratio of reversible fouling, resulted in the mitigation of the frequency of chemical cleaning.
In water treatment process using microfiltration membranes, manganese is a substance that causes inorganic membrane fouling. As a result of analysis on the operation data taken from I WTP(Water Treatment Plant), it was confirmed that the increase of TMP was very severe during the period of manganese inflow. The membrane fouling fastened the increase of TMP and shortened the service time of filtration or the cleaning cycle. The TMP of the membrane increased to the maximum of 2.13 kgf/cm2, but it was recovered to the initial level (0.17 kgf/cm2) by the 1st acid cleaning step. It was obvious that the main membrane fouling contaminants are due to inorganic substances. As a result of the analysis on the chemical waste, the concentrations of aluminum(146-164 mg/L) and manganese(110-126 mg/L) were very high. It is considered that aluminum was due to the residual unreacted during coagulation step as a pretreatment process. And manganese is thought to be due to the adsorption on the membrane surface as an adsorbate in feed water component during filtration step. For the efficient maintenance of the membrane filtration facilities, optimization of chemical concentration and CIP conditions is very important when finding the abnormal level of influent including foulants such as manganese.
멤브레인 파울링은 지표수를 처리하는 저압 멤브레인 기술 적용의 확장에 있어 큰 장애가 된다. 따라서 파울링 제어를 위한 주기적인 수리학적 세정기술의 최적화는 매우 중요하다. 주기적인 수리학적 세정과 이와 연관된 파울링 현상에 관한 올바른 이해는 멤브레인 세정 전략을 최적화하기 위해 매우 유용할 수 있다. 실험적으로 측정한 투과도와 전통적인 Hermia 파울링 모델 예측 치의 비교를 통해, 본 연구에서는 합성 탁도유발 시료를 처리하는 가압식 멤브레인 공정에서 30분 여과와 정세정/역세정이 포함된 1분 세정조건을 바탕으로 6번의 운전사이클을 통해 발생하는 파울링 현상을 분석하고 이를 통해 지배적인 파울링 기작을 정량적으로 이해하고자 하였다. 단독 세정에서, 첫 번째 운전사이클에서 발생하는 파울링은 완 전공극막힘 현상에 의해 주로 지배되었고 마지막 운전 사이클에서는 케이크 형성이 지배적인 파울링 기작으로 관찰되었다. 정세정과 역세정이 혼합된 경우, 파울링 속도는 감소하였으나 전반적으로 케이크 형성이 주 파울링 기작으로 관찰되었다.
In this work, we studied systematically the effects of NCIF on defouling for a range of solutes that foul (BSA protein) and form cakes (alumina colloids) on the membrane thereby causing severe reduction in the flux. Changing the gravitational orientation of the batch cell induces NCIF in the membrane module and higher inclined angle offers stronger NCIF. This induced NCIF enhances back transport of the deposited solutes away from the membrane surface, therefore gives for the improvement of membrane performance. The flux results according to the inclined angles (from 0° to 180°) of the batch cell were analyzed by the pore blocking filtration model. It was shown that NCIF reduced the fouling of intermediate pore blocking by about 66% at the beginning of UF operation, and thereafter reduced the fouling of cake filtration by about 98%.
본 연구에서는 역전기투석 공정에서 발생 가능한 막오염 현상을 in-situ로 측정하기 위하여 임피던스 스펙트로스 코피 방법을 도입하여 실제 발생한 막오염 현상 측정 방법을 제시하였다. 얻어진 임피던스 데이터를 활용하여 Nyquist 도시 법과 어드미턴스 도시법으로 스펙트럼을 도시하였으며 두 도시법 모두 유의미한 막오염 현상을 감지할 수 있었다. 또한 초기 막오염 현상에서 음이온 교환막 표면에 막오염물의 불안정한 축적 현상 및 역전기투석 공정의 운전 시간에 따른 막오염층의 구조적 변화를 감지할 수 있었다.
In this paper, we investigate the characteristics of membrane fouling caused by water temperature in the Membrane bioreactor(MBR) process and try to derive the membrane fouling control by chemical enhanced backwashing(CEB). The extracellular polymeric substances(EPS) concentration was analyzed according to the water temperature in the MBR, and the membrane fouling characteristics were investigated according to the conditions, with sludge & without sludge, through a lab-scale reactor. As shown in the existing literature the fouling resistance rate was increased within sludge with the water temperature was lowered. However, in the lab-scale test using the synthetic wastewater, the fouling resistance increased with the water temperature. This is because that the protein of the EPS was more easily adsorbed on the membrane surface due to the increase of entropy due to the structural rearrangement of the protein inside the protein as the water temperature increases. In order to control membrane fouling, we tried to derive the cleaning characteristics of CEB by using sodium hypochlorite(NaOCl). We selected the condition with the chemicals and the retention time, and the higher the water temperature and the chemical concentration are the higher the efficiencies. It is considered that the increasing temperature accelerated the chemical reaction such as protein peptide binding and hydrolysis, so that the attached proteinaceous structure was dissolved and the frequency of the reaction collision with the protein with the chemical agent becomes higher. These results suggest that the MBRs operation focus on the fouling control of cake layer on membrane surface in low temperatures. On the other hand, the higher the water temperature is the more the operation strategies of fouling control by soluble EPS adsorption are needed.
Recently EC-MBR (Elctrocoagulation - Membrane Bio Reactor) has been suggested as one of alternative processes to overcome membrane fouling problems. Most important operational parameters in the EC-MBR are known to current density and contact time. Their effect on membrane filtration performances has been reported well, however, quantitative interrelationship between both parameters not been investigated yet. The purpose of this study is to give a kinetic model suggesting the current density and the contact time required to reduce the membrane fouling. The 4 different set of current densities (2.5, 6, 12 and 24 A/m2) and contact times (0, 2, 6 and 12 hr) were selected as operational parameters. After each electro-coagulation under the 16 different conditions, a series of membrane filtration was carried out. The membrane fouling decreased as the current density and contact time increased, Total fouling resistances under different conditions, Rt(=Rc+Rf) were calculated and compared to those of the controls (R0), which were calculated from the data of experiments without electro-coagulation. A kinetic approach for the fouling reduction rate (Rt / R0) was carried out and the equation ρi0.46t=7.0 was obtained, which means that the product of current density and the contact time needed to reduce the fouling in certain amounts (in this study, 10% of fouling reduction) is always constant.
분리막 장치는 액체, 기체의 물질분리를 위해 다양한 산업분야에 적용되어 왔다. 특히 액체 분리에 적용되는 분리막 장치는 수처리분야, 화학산업공정, 바이오산업공정, 의약분야 등으로 확장되면서 분리정제 공정에 보편적인 기술로 자리잡았다. 분리막 공정은 막 특성상 분리되는 물질에 따라 다양한 막힘현상이 발생하는데, 이러한 막힘현상을 방지하기 위해 막과 시스템이 발전하여왔고, 시스템 분야에서는 막힘현상을 방지하기 위해 진동, 회전, 와류 등을 이용하여 막표면에 발생하는 막힘현상을 억제하는 모듈들이 개발되어 상용화되고 있고, 이런 설비들을 Dynamic filtration 설비로 구분하고 있다. Dynamic filtration 설비들 중에서 특히, 와류를 이용하는 Anti-Fouling Membrane System(FMX)은 고농도 고점도 특성을 갖는 용액에서 물질을 분리하는 성능이 우수하여, 최근 급성장하는 바이오산업분야의 생산공정에 다양하게 적용되고 있다.
막여과 수처리 공정에서 막오염은 플럭스 감소나 막간차압 증가를 야기하는 중요한 문제로 남아있다. 막오염을 저감하는 여러 가지 방법 중, 막의 표면에 패턴을 입혀 그 패턴의 형상에 따라 유체의 이동을 변화시킴으로써 막오염을 저감시키는 방법이 연구되어 왔다. 특히 45° 회전된 피라미드 패턴은 피라미드 패턴에 비해 막오염 저감 효과가 크다는 연구결과가 있었다. 본 연구에서는 비용매상분리법과 소프트리소그래피(soft-lithograhy)를 이용하여 막의 표면에 45° 회전된 피라미드 패턴을 입히고, 크기가 다른 입자를 포함한 원수를 여과하면서 막오염 저감 효과를 비교해 보았다.
This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.
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.
무기실리카 입자로 구성된 고탁도 원수를 처리하는 침지식 정밀여과 운전에서 휴민산과 2가 양이온의 존재유무에 따라 시간에 따른 파울링 저항을 관찰하였다. 공기폭기로 인한 무기실리카 입자의 파울링 감소효과는 휴민산과 칼슘이 혼합 으로 존재 시 감소하였다. 파울링층의 전자현미경 관찰결과 칼슘의 존재 시 휴민산의 무기실리카 입자 표면흡착이 관찰되었 다. 이는 멤브레인 표면에 조밀한 파울링층을 형성시켜 공기폭기 효과를 감소시킨 것으로 판단된다. 용액의 조성에 따른 고탁 도 원수의 탁도 제거율에는 큰 변화가 없었으나 공기폭기량에 따라 칼슘과 무기실리카 입자의 혼합 존재 시 유기물질의 제거 율은 80% 이상으로 증가하였다. 이는 공기폭기 하에 무기실리카 입자 표면에 흡착된 일부 휴민산들이 멤브레인 표면으로부 터 함께 역수송 되어 유기물질 제거율을 증가시킨 것으로 사료된다.
A membrane module including grid was designed and introduced to MBR (membrane bio-reactor) for the purpose of better control of membrane fouling. It could be anticipated that the grid enhances the shear force of fluid-air mixture into the membrane surface by even-distributing the fluid-air to the membrane module. As MLSS concentration, packing density which is expressed in the ratio of the housing and the cross-sectional area of membrane fibers (Am/At) and air-flow rate were changed, membrane foulings were checked by monitoring fouling resistances. The total fouling resistance (Rc+Rf) without grid installation (i.e., control) was 2.13×1012 m-1 , whereas it was reduced to 1.69×1012 m-1 after the grid was installed. Regardless of the grid installation, the Rc+Rf increased as the packing density increased from 0.09 to 0.28, however, the increment of resistance for the grid installation was less than that of the control. Increase in the air flow rate did not always guarantee the reduction of fouling resistance, indicating that the higher air flow rate can partially de-flocculate the activated sludge flocs, which led to severer membrane fouling. Consequently, installation of grids inside the housing have brought a beneficial effect on membrane fouling and optimum air flow rate is important to keep the membrane lowering fouling.
수처리용 분리막 여과 공정에서 막오염의 문제는 여전히 해결해야 할 난제이다. 막오염 현상을 제어하기 위한 방안으로 막표면에 패턴을 도입하는 방법이 연구되어 왔다. 분리막의 패턴은, 막표면에서의 유체 흐름에 변화를 일으켜 오염물이 쌓이지 않게 하거나 쌓인 오염물이 일부 떨어져 나가는 효과를 주는 것 으로 보고된 바 있다. 본 연구에서는 수처리용 패턴 분리막을 제조하고, 패턴의 막오염 방지 효과를 평가하고자 하였다. 이를 위하여 CFD 기법을 이용하여 유 체 흐름을 시뮬레이션으로 분석하고, 시뮬레이션 결과와 실제 실험 결과를 비교 분석하기 위해 구형의 모델 입자로 막여과 실험을 수행하였다. 다양한 크기의 모델 입자를 이용함으로써 오염물의 크기에 따른 패턴의 막오염 방지 효과를 분석해 보고자 하였다.
새로운 알루미나 (Al2O3)와 실리카(SiO2)로 이루어진 규산알루미나질 납석광물을 적용하여 세라믹 지지체를 개발하고 수처리 적용가능성을 평가하였다. 납석 세라믹 지지체의 순수투과도는 약 1370 L/m2.hr.bar 였으며 지표수의 탁도 및 유기물의 제거율은 각각 98 %와 75 %였다. 실 하수처리장 MBR의 MLSS를 취수하여 실험한 결과 완벽한 SS 제거효율을 나타내었다. 모듈간격에 따른 납석지 지체 파울링 현상을 관찰한 결과 모듈간격이 증가할수록 파울링은 감소하였으나 일정 모듈간격(3.5 cm)이상인 경우 파울링은 증가하였고 이는 공기 폭기량이 증가할수록 증가하는 경향을 나타내었다.
기후 변화 및 상수원 오염 등으로 원수 내 조류 증식의 빈도가 높아짐에 따라 모래여과와 마찬가지로 막여과 정수처리 공정 운영에서도 문제를 유발할 수 있기 때문에 이에 대한 기술적 대응 방안이 수립되어야 한다. 특히 우리나라와 같이 계절적 구분이 뚜렷한 지역에서 조류는 수온에 따라 우점하는 조류의 종이 변화하여, 외형 적 형태 및 성상이 종별로 다른 조류의 특성을 감안한 대처 방안이 검토되어야 한 다. 본 연구는 낙동강 수계를 원수로 하는 500m3/d 규모의 파일럿 플랜트를 이용하여 계절별로 상이하게 유입되는 조류의 분류에 따라 겨울철 저수온 시기에 규조류가 번성할 경우 염기 역세정 방법을 적용하고, 여름철 시기에 남조류가 번성할 경우에는 분말활성탄으로 처리하는 조류 대응 막여과 운전 방법과 전처리 공정에 대해 검토하였다.