Effect of coagulation mechanisms on the fouling and ultrasonic cleaning of PTFE membrane

2012 ◽  
Vol 66 (11) ◽  
pp. 2291-2298 ◽  
Author(s):  
Meng-Wei Wan ◽  
Cybelle Morales Futalan ◽  
Cheng-Hung Chang ◽  
Chi-Chuah Kan
Keyword(s):  
Membrane Fouling ◽  
Permeate Flux ◽  
Cleaning Efficiency ◽  
Ultrasonic Cleaning ◽  
Ptfe Membrane ◽  
Pore Blocking ◽  
Dead End ◽  
Flux Decline ◽  
Cake Formation ◽  
Scanning Electron

In this study, the effect of coagulation pretreatment on membrane fouling and ultrasonic cleaning efficiency was investigated using a dead-end polytetrafluoroethylene (PTFE) microfiltration system. The extent of membrane fouling was examined under different coagulation mechanisms such as charge neutralization (CN), electrostatic patch effect (EPE) and sweep flocculation (SW). Fouling through EPE mechanism provided the greatest flux decline and least permeate flux recovery over CN and SW. EPE produces more stable, smaller and more compact flocs while CN and SW have large, easily degraded and highly-branched structured flocs. The predominant fouling mechanism of EPE, CN and SW is pore blocking, a combination of pore blocking and cake formation, and cake formation, respectively. Better permeate flux recovery is observed with SW over CN and EPE, which implies formation of less dense and more porous cake deposits. The morphology of fouled membranes was examined using scanning electron microscopy (SEM).

scholarly journals Interdependence of Contributing Factors Governing Dead-End Fouling of Nanofiltration Membranes

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 47
Author(s):  
Oranso Themba Mahlangu ◽  
Bhekie Brilliance Mamba
Keyword(s):  
Membrane Surface ◽  
Contact Angles ◽  
Permeate Flux ◽  
Contributing Factors ◽  
Pore Blocking ◽  
Dead End ◽  
Flux Decline ◽  
Cake Formation ◽  
Affinity Interaction

Cake-enhanced concentration polarization (CECP) has been ascribed as the main cause of flux decline in dead-end filtration. An unfamiliar approach was used to investigate the role of CECP effects in the fouling of a nanofiltration membrane (NF-270) that poorly reject salts. Membrane–foulant affinity interaction energies were calculated from measured contact angles of foulants and membrane coupons based on the van der Waals/acid–base approach, and linked to resistance due to adsorption (Ra). In addition, other fouling mechanisms and resistance parameters were investigated using model organic and colloidal foulants. After selection, the foulants and membranes were characterized for various properties, and fouling experiments were conducted under controlled conditions. The fouled membranes were further characterized to gain more understanding of the fouling layer properties and flux decline mechanisms. Sodium alginate and latex greatly reduced membrane permeate flux as the flux declined by 86% and 59%, respectively, while there was minor flux decline when aluminum oxide was used as model foulant (<15% flux decline). More flux decline was noted when fouling was conducted with a combination of organic and colloidal foulants. Contrary to other studies, the addition of calcium did not seem to influence individual and combined fouling trends. Foulants adsorbed more on the membrane surface as the membrane–foulant affinity interactions became more attractive and pore blocking by the foulants was not important for these experiments. Hydraulic resistance due to cake formation (Rc) had a higher contributing effect on flux decline, while CECP effects were not substantial.

scholarly journals Studies of polypropylene membrane fouling during microfiltration of broth with Citrobacter freundii bacteria

2015 ◽  
Vol 17 (4) ◽  
pp. 56-64 ◽  
Author(s):  
Marek Gryta ◽  
Marta Waszak ◽  
Maria Tomaszewska
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Transmembrane Pressure ◽  
Citrobacter Freundii ◽  
Permeate Flux ◽  
Process Duration ◽  
Polypropylene Membrane ◽  
Flux Decline ◽  
Cake Layer ◽  
Scanning Electron

Abstract In this work a fouling study of polypropylene membranes used for microfiltration of glycerol solutions fermented by Citrobacter freundii bacteria was presented. The permeate free of C. freundii bacteria and having a turbidity in the range of 0.72–1.46 NTU was obtained. However, the initial permeate flux (100–110 L/m2h at 30 kPa of transmembrane pressure) was decreased 3–5 fold during 2–3 h of process duration. The performed scanning electron microscope observations confirmed that the filtered bacteria and suspensions present in the broth formed a cake layer on the membrane surface. A method of periodical module rinsing was used for restriction of the fouling influence on a flux decline. Rinsing with water removed most of the bacteria from the membrane surface, but did not permit to restore the initial permeate flux. It was confirmed that the irreversible fouling was dominated during broth filtration. The formed deposit was removed using a 1 wt% solution of sodium hydroxide as a rinsing solution.

scholarly journals Potential Pitfalls in Membrane Fouling Evaluation: Merits of Data Representation as Resistance Instead of Flux Decline in Membrane Filtration

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 460
Author(s):  
Bastiaan Blankert ◽  
Bart Van der Bruggen ◽  
Amy E. Childress ◽  
Noreddine Ghaffour ◽  
Johannes S. Vrouwenvelder
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Data Representation ◽  
Strong Impact ◽  
Experimental Conditions ◽  
Permeable Membrane ◽  
Dead End ◽  
Flux Decline ◽  
The Difference ◽  
Filtration Flux

The manner in which membrane-fouling experiments are conducted and how fouling performance data are represented have a strong impact on both how the data are interpreted and on the conclusions that may be drawn. We provide a couple of examples to prove that it is possible to obtain misleading conclusions from commonly used representations of fouling data. Although the illustrative example revolves around dead-end ultrafiltration, the underlying principles are applicable to a wider range of membrane processes. When choosing the experimental conditions and how to represent fouling data, there are three main factors that should be considered: (I) the foulant mass is principally related to the filtered volume; (II) the filtration flux can exacerbate fouling effects (e.g., concentration polarization and cake compression); and (III) the practice of normalization, as in dividing by an initial value, disregards the difference in driving force and divides the fouling effect by different numbers. Thus, a bias may occur that favors the experimental condition with the lower filtration flux and the less-permeable membrane. It is recommended to: (I) avoid relative fouling performance indicators, such as relative flux decline (J/J0); (II) use resistance vs. specific volume; and (III) use flux-controlled experiments for fouling performance evaluation.

Membrane fouling mechanisms and permeate flux decline model in soy sauce microfiltration

2017 ◽  
Vol 41 (1) ◽  
pp. e12599 ◽  
Author(s):  
Ye Sun ◽  
Zhen Qin ◽  
Liming Zhao ◽  
Qiming Chen ◽  
Qingyun Hou ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Soy Sauce ◽  
Permeate Flux ◽  
Flux Decline

Electroflocculation as potential pretreatment in colloid ultrafiltration

2006 ◽  
Vol 6 (1) ◽  
pp. 69-78 ◽  
Author(s):  
T. Harif ◽  
M. Hai ◽  
A. Adin
Keyword(s):  
Membrane Fouling ◽  
Colloidal Suspension ◽  
Membrane Surface ◽  
Constant Current ◽  
Permeate Flux ◽  
Batch Mode ◽  
Membrane Behavior ◽  
Flux Decline ◽  
Stainless Steel Cathode ◽  
Marginal Improvement

Electroflocculation (EF) is a coagulation/flocculation process in which active coagulant species are generated in situ by electrolytic oxidation of an appropriate anode material. The effect of colloidal suspension pretreatment by EF on membrane fouling was measured by flux decline at constant pressure. An EF cell was operated in batch mode and comprised two flat sheet electrodes, an aluminium anode and stainless steel cathode, which were immersed in the treated suspension, and connected to an external DC power supply. The cell was run at constant current between 0.06–0.2A. The results show that pre-EF enhances the permeate flux at pH 5 and 6.5, but only marginal improvement is observed at pH 8. At all pH values cake formation on the membrane surface was observed. The differences in membrane behavior can be explained by conventional coagulation theory and transitions between aluminium mononuclear species which affect particle characteristics and consequently cake properties. At pH 6.5, where sweep floc mechanism dominates due to increased precipitation of aluminium hydroxide, increased flux rates were observed. It is evident that EF can serve as an efficient pretreatment to ultrafiltration of colloid particles.

Investigation of membrane fouling by synthetic and natural particles

2004 ◽  
Vol 50 (12) ◽  
pp. 279-285 ◽  
Author(s):  
J.H. Kweon ◽  
D.F. Lawler
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Research Articles ◽  
Clay Material ◽  
Dramatic Effect ◽  
Flux Decline ◽  
Scanning Electron

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. Numerous research articles have indicated that either particles or natural organic matter (NOM) has been the most detrimental foulant. Therefore, the role of particles in membrane fouling was investigated with two synthetic waters (having either particles alone or particles with simple organic matter) and a natural water. Membrane fouling was evaluated with flux decline behavior and direct images from scanning electron microscopy. The results showed that the combined fouling by kaolin and dextran (a simple organic compound selected as a surrogate for NOM) showed no difference from the fouling with only the organic matter. The similarity might stem from the fact that dextran (i.e., polysaccharide) has no ability to be adsorbed on the clay material, so that the polysaccharide behaves the same with respect to the membrane with or without clay material being present. In contrast to kaolin, the natural particles showed a dramatic effect on membrane fouling.

Fouling of nanofiltration membranes used for separation of fermented glycerol solutions

2014 ◽  
Vol 68 (6) ◽  
Author(s):  
Justyna Bastrzyk ◽  
Marek Gryta ◽  
Krzysztof Karakulski
Keyword(s):  
Membrane Fouling ◽  
Lactobacillus Casei ◽  
Permeate Flux ◽  
Nanofiltration Membranes ◽  
Second Stage ◽  
Flux Decline ◽  
Colloidal Fouling ◽  
Treatment Stage ◽  
Pre Treatment ◽  
Two Stages

AbstractIn this study, the glycerol solutions were fermented using Lactobacillus casei bacteria. The broths were pre-treated by microfiltration, followed by a further separation with nanofiltration. The latter process was carried out in two stages, using the NF270 and NF90 membranes, respectively. The concentrates thus obtained were enriched with citric acid (first stage) and then with lactic acid and glycerol (second stage). By means of SEM and AFM microscopy, as well as ATR-FTIR analysis, the intensity of membrane-fouling was studied. The colloidal fouling and bio-fouling caused a more than two-fold decrease in the permeate flux during microfiltration of the broth. This pre-treatment stage was effective, and a permeate turbidity of less than 0.2 NTU was obtained. However, the nanofiltration membranes exhibited a 30 % flux decline over the course of the process, mainly due to the organic fouling.

Evaluation of Permeate Flux Rate and Membrane Fouling in Dead-End Microfiltration of Primary Sewage Effluent

2005 ◽  
Vol 22 (4) ◽  
pp. 427-439 ◽  
Author(s):  
C.M. Modise ◽  
H.F. Shan ◽  
R.D. Neufeld ◽  
R.D. Vidic
Keyword(s):  
Membrane Fouling ◽  
Sewage Effluent ◽  
Flux Rate ◽  
Permeate Flux ◽  
Dead End

Effects of flocculent aggregates on microfiltration with coagulation pretreatment of high turbidity waters

2006 ◽  
Vol 53 (7) ◽  
pp. 191-197 ◽  
Author(s):  
S. Lee ◽  
J. H. Kweon ◽  
Y. H. Choi ◽  
K.-H. Ahn
Keyword(s):  
Drinking Water ◽  
Membrane Fouling ◽  
Raw Water ◽  
Cleaning Efficiency ◽  
Membrane Cleaning ◽  
Han River ◽  
Turbid Waters ◽  
Flux Decline ◽  
Negative Effect ◽  
High Turbidity

Immersed membrane systems, and those with in-line coagulation, have been extensively applied in drinking water systems. Sedimentation is usually replaced by membrane processes in both systems. In these systems, voluminous flocculent aggregates formed during coagulation could be potential foulants. When raw waters with high turbidity are introduced, particle loadings to membrane due to coagulation pretreatment are enormous and thus could increase fouling. In general, during the rainy season, the turbidity of the Han River water, which supplies drinking water for the City of Seoul, Korea, is more than a hundred times higher than usual. Therefore, effects of floc on membrane fouling were investigated with highly turbid waters. Two turbidity concentrations, 40 and 200 NTU, were formulated by the addition of kaolin (used as a natural particle surrogate) to the Han River raw water. The results showed that the flux decline behaviours of the highly turbid waters were different from those of natural raw water. Coagulation pretreatment was very effective at reducing membrane fouling. Flocculent aggregates showed a negative effect on the flux decline, but a positive effect on the membrane cleaning efficiency.

Fouling of a polyethersulfone ultrafiltration membrane by natural organic matter

2004 ◽  
Vol 4 (4) ◽  
pp. 205-212 ◽  
Author(s):  
G. Makdissy ◽  
J.-P. Croué ◽  
G. Amy ◽  
H. Buisson
Keyword(s):  
Natural Organic Matter ◽  
Surface Waters ◽  
Membrane Fouling ◽  
Adsorption Mechanism ◽  
Transmembrane Pressure ◽  
Membrane Flux ◽  
Dead End ◽  
Flux Decline ◽  
Hydrophilic Fraction ◽  
Significant Flux

This research focused on membrane flux decline trends observed during ultrafiltration (UF) of solutions of NOM fractions isolated from surface waters. All filtration experiments were performed with a non-stirred dead-end cell unit equipped with flat sheet polyethersulfone PES UF membrane coupons under a constant transmembrane pressure of 1 bar. Results showed that the most significant flux decline was due to the organic colloid fraction, a hydrophilic fraction consisting mostly of bacterial cell wall residues. This research demonstrated that these colloids which incorporate 2/3 of dissolved organic structures (&lt;0.45 μm) and 1/3 of particulate organics exert strong fouling properties due to both rejection phenomena and the adsorption mechanism. The fouling contribution by humic-like materials depends on their origin and nature. Aromaticity appears to be a secondary parameter which influences membrane fouling. Polysaccharides, proteins and amino sugars also largely present in humic-like structures (supramolecular structure) play an important role in UF membrane fouling. The perspective of NOM as a biopolymer mixture can contribute to an understanding of membrane fouling.

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