Investigation of membrane fouling in ultrafiltration using model organic compounds

2005 ◽  
Vol 51 (6-7) ◽  
pp. 101-106 ◽  
Author(s):  
J.H. Kweon ◽  
D.F. Lawler
Keyword(s):  
Organic Compounds ◽  
Membrane Fouling ◽  
Alginic Acid ◽  
Membrane Surface ◽  
Sem Images ◽  
Membrane Processes ◽  
Xps Spectra ◽  
Relative Composition ◽  
Flux Decline ◽  
The City

Natural organic matter (NOM) is known to be the worst foulant in the membrane processes, but the complexities of NOM make it difficult to determine its effects on membrane fouling. Therefore, simple organic compounds (surrogates for NOM) were used in this research to investigate the fouling mechanisms in ultrafiltration. Previous research on NOM components in membrane processes indicated that polysaccharides formed an important part of the fouling cake. Three polysaccharides (dextran, alginic acid, and polygalacturonic acid) and a smaller carbohydrate (tannic acid) were evaluated for their removal in softening (the treatment process in the City of Austin). Two polysaccharides (dextran and alginic acid) were selected and further investigated for their effects on membrane fouling. The two raw organic waters (4 mg/L C) showed quite different patterns of flux decline indicating different fouling mechanisms. Softening pretreatment was effective to reduce flux decline of both waters. The SEM images of the fouled membrane clearly showed the shapes of deposited foulants. The high resolution results of the XPS spectra showed substantially different spectra of carbon, C(1s), in the membrane fouled by two raw organic waters. The XPS was beneficial in determining the relative composition of each fouling material on the membrane surface.

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.

Monitoring of CaSO4 deposition behaviors on biofilm during nanofiltration via ultrasonic time-domain reflectometry (UTDR)

2010 ◽  
Vol 61 (11) ◽  
pp. 2853-2861 ◽  
Author(s):  
Y. L. Hou ◽  
J. X. Li ◽  
Y. N. Gao ◽  
X. C. Xu ◽  
Y. Cai ◽  
...  
Keyword(s):  
Time Domain ◽  
Pressure Effect ◽  
Membrane Surface ◽  
Time Domain Reflectometry ◽  
Sem Images ◽  
Differential Signal ◽  
Flux Decline ◽  
Ultrasonic Time ◽  
Ultrasonic Measurements ◽  
Non Destructive

The ultrasonic time-domain reflectometry (UTDR) as a non-destructive real-time method was employed to monitor the CaSO4 deposition behaviors on biofilm during nanofiltration (NF). Two parallel experiments were performed to compare the different behaviors of CaSO4 deposition with and without biofilm on the membrane. Results showed that the flux decline during combined fouling was slower than that in case of CaSO4 fouling alone. The Ca2 +  rejection obtained with biofilm was higher than that without. A larger acoustic differential signal obtained by UTDR in the combined fouling revealed a denser and thicker layer formed on the membrane surface. Furthermore, the amount of CaSO4 deposition on the biofouled membrane was more than that on non-biofouled membrane as a result of microorganisms as crystal nucleus to induce CaSO4 crystallization and deposition. SEM images indicate that the CaSO4 crystals deposited in order on the non-biofouled membrane, whereas on the biofouled membrane they were embedded in the biofilm. The denser and thicker fouling layer formed with biofilm was impermeable, resulting in a high Ca2 +  rejection. The complexation of Ca with polysaccharide in biofilm would eliminate the cake-enhanced osmotic pressure effect leading to a slow flux decline. To sum up, the independent measurements corroborate the ultrasonic measurements.

Experimental test to evaluate performance of an anaerobic reactor provided with an external membrane unit

1998 ◽  
Vol 38 (8-9) ◽  
pp. 385-392 ◽  
Author(s):  
S. Elmaleh ◽  
L. Abdelmoumni
Keyword(s):  
Membrane Fouling ◽  
Industrial Development ◽  
Particle Deposition ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Unit ◽  
Anaerobic Reactor ◽  
Flux Decline ◽  
Aerobic Reactor ◽  
Sludge Production

The coupling of a wastewater treatment anaerobic reactor with a microfiltration or ultrafiltration membrane is particularly attractive: lower sludge production than in an aerobic reactor, methane production and dissociation of the mean residence times of the different phases. However, the industrial development of such a process is hampered by membrane fouling which can be a result of many causes and require a comprehensive study especially fouling by anaerobic suspensions. In order to simplify the study, the different phases of anaerobic oxidation were separated and this work is focused on the filtration of an anaerobic suspension fed with acetic acid as the sole carbon source at 2 g/l TOC. The effluent quality was excellent without sludge production in spite of large variation of the liquid phase space time. The tested filtration elements were tubular Carbosep membranes. The M14 membrane showed the greatest flux of 120 l/m2 h at 0.5 bar and 25 Pa shear stress and the flux increased to 180 l/m2 h when a baffle was introduced. The main fouling mechanism appears to be the particle deposition on the membrane surface as no flux decline was observed at higher cross-flow velocity.

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.

The significance of interactions between organic compounds on low pressure membrane fouling

2011 ◽  
Vol 64 (3) ◽  
pp. 632-639 ◽  
Author(s):  
S. R. Gray ◽  
N. Dow ◽  
J. D. Orbell ◽  
T. Tran ◽  
B. A. Bolto
Keyword(s):  
Organic Compounds ◽  
Membrane Fouling ◽  
Membrane Filtration ◽  
Alginic Acid ◽  
Hollow Fibre ◽  
Acid Solutions ◽  
Small Molecular Weight ◽  
Filtration Apparatus ◽  
Hydrophilic Membranes ◽  
Hydrophilic Membrane

Fouling of hollow fibre microfiltration and ultrafiltration membranes by solutions of pure organic compounds and mixtures of these compounds was studied with a backwashable membrane filtration apparatus. Small molecular weight compounds resulted in little fouling, while their polymeric analogues resulted in more severe fouling. Neutrally charged dextran resulted in minor, irreversible fouling, that was considered to be associated with blocking of small pores. Cationically charged chitosan produced gross fouling for which the extent of reversibility increased with salt addition. Anionically charged alginic acid resulted in gross irreversible fouling, except when being filtered by a hydrophilic membrane in the absence of calcium where a high degree of flux recovery was observed. Calcium addition to the alginic acid solutions resulted in gross fouling of all membranes and calcium bridging was considered to be responsible for this behaviour. Greater fouling occurred on the hydrophilic membrane compared to the hydrophobic membranes for bovine serum albumin (BSA) solutions, and this was considered to be due to physical blocking of pores, because addition of calcium resulted in lower flux declines. Addition of BSA and calcium to alginic acid solutions resulted in lower flux recoveries for the alginic acid system, consistent with the proposition that interactions between polysaccharide and other compounds are required for irreversible fouling on hydrophilic membranes.

Characteristics of Fouled and Chemically Cleaned Membrane

2014 ◽  
Vol 1073-1076 ◽  
pp. 751-754
Author(s):  
Jun Xia Liu ◽  
Bing Zhi Dong ◽  
Wei Wei Huang
Keyword(s):  
Natural Organic Matter ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Flux Measurement ◽  
Flux Analysis ◽  
Chemical Cleaning ◽  
Cleaning Agents ◽  
Flux Decline ◽  
Ftir Spectrometry ◽  
Scanning Electron

The main objective of this study was to investigate membrane fouling caused by natural organic matter (NOM). Flux measurement, fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM) were employed to compare the surface morphology of fouled membrane and chemically cleaned membrane. Sodium hypochlorite (NaClO), sodium hydroxide (NaOH), hydrochloric acid (HCl) were used as chemical cleaning agents respectively. Flux analysis demonstrated that chemical cleaning have little effect on flux recovery. FTIR spectrometry revealed that polysaccharide and protein took the major responsibility for membrane fouling. SEM showed that foulants filled the pores and blocked the membrane surface which led to the flux decline.

Effects of characteristics of softening as a pretreatment for ultrafiltration

2003 ◽  
Vol 3 (5-6) ◽  
pp. 429-435
Author(s):  
J.H. Kweon ◽  
D.F. Lawler
Keyword(s):  
Membrane Fouling ◽  
Particle Concentration ◽  
Membrane Surface ◽  
Feed Water ◽  
Independent Variables ◽  
Organic Matter Concentration ◽  
Flux Decline ◽  
Slow Kinetics ◽  
Matter Concentration ◽  
Kinetics Of

Softening was proposed as a pretreatment for ultrafiltration, which reduces foulants prior to membrane processes. The objectives of this research were to understand the nature of the fouling mechanisms for ultrafiltration when used for waters that either require softening or have been softened, and to use that understanding to determine promising options for the use of softening as a pretreatment before ultrafiltration (UF). Several characteristics of softening, including extent of softening, precipitation kinetics, and hydrophobicity of membrane materials, were investigated as independent variables. Because of softening, both the organic matter concentration and the particle concentration of feed water to ultrafiltration were reduced, thus reducing the degree of fouling. The slow kinetics of softening had little effect on membrane fouling although precipitation directly occurred on the membrane surface in the system during the operation. Detailed images of the membrane surface obtained by scanning electron microscopy confirmed substantial amounts of the precipitates on the surface. In contrast, the hydrophobicity of the membrane material showed a significant effect on the flux decline behavior. Overall, the integrated water treatment of softening and ultrafiltration is shown to be a promising option for hard waters.

scholarly journals An Investigation on the Application of Pulsed Electrodialysis Reversal in Whey Desalination

2019 ◽  
Vol 20 (8) ◽  
pp. 1918 ◽  
Author(s):  
Arthur Merkel ◽  
Amir M. Ashrafi
Keyword(s):  
Contact Angle ◽  
Anion Exchange ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Contact Angle Measurement ◽  
Angle Measurement ◽  
Anion Exchange Membranes ◽  
Sem Images ◽  
Short Pulses ◽  
Back Transfer

Electrodialysis (ED) is frequently used in the desalination of whey. However, the fouling onto the membrane surface decreases the electrodialysis efficiency. Pulsed Electrodialysis Reversal (PER), in which short pulses of reverse polarity are applied, is expected to decrease the fouling onto membrane surface during ED. Three (PER) regimes were applied in the desalination of acid whey (pH ≤ 5) to study their effects on the membrane fouling and the ED efficiency. The PER regimes were compared to the conventional ED as the control. For each regime, two consecutive runs were performed without any cleaning step in-between to intensify the fouling. After the second run, the membranes were subjected to the Scanning electron microscope (SEM) imaging and contact angle measurement to investigate the fouling on the membrane surface in different regimes. The ED parameters in the case of conventional ED were almost the same in the first and the second runs. However, the parameters related to the ED efficiency including ED capacity, ash transfer, and ED time, were deteriorated when the PER regimes were applied. The contact angle values indicated that the fouling on the diluate side of anion exchange membranes was more intensified in conventional ED compared to the PER regimes. The SEM images also showed that the fouling on the diluate side of both cation and anion exchange membranes under PER regimes was reduced in respect to the conventional ED. However, the back transfer to the diluate compartment when the reverse pulse was applied is dominant and lowers the ED efficiency slightly when the PER is applied.

The use of nanofiltration for the removal of pesticides from groundwater: an evaluation

2001 ◽  
Vol 1 (2) ◽  
pp. 99-106 ◽  
Author(s):  
B. Van der Bruggen ◽  
K. Everaert ◽  
D. Wilms ◽  
C. Vandecasteele
Keyword(s):  
Dipole Moment ◽  
Membrane Fouling ◽  
Solid Phase ◽  
Membrane Surface ◽  
Water Flux ◽  
Molecular Size ◽  
Effective Diameter ◽  
Molecular Configuration ◽  
Groundwater Flux ◽  
Flux Decline

This study explores the combined removal of four pesticides (atrazine, simazine, diuron, isoproturon) and hardness from groundwater with nanofiltration (NF). Four NF membranes were used: NF45 and NF70 (Dow/FilmTec), and UTC-20 and UTC-60 (Toray Ind. Inc.). Each pesticide was added to groundwater samples in a concentration of 1 μg/l, representative for contaminated sources. For the determination of pesticides in such low concentrations, an analytical method using solid-phase extraction and high performance liquid chromatography was elaborated. The retentions with NF were compared and explained by means of molecular size and dipole moment. Molecular size, expressed as an effective diameter representing the projection of the molecule on the membrane surface, was calculated by determining the energetically most favourable molecular configuration. The largest molecules had the highest retentions, when all other properties are comparable. A high dipole moment decreases retentions because of charge interactions with the membrane. The hardness retentions were high. For drinking water production, it might be necessary to add hardness after filtration. The groundwater flux was approximately 5% lower compared to the distilled water flux. This relatively small flux decline indicates pore blocking due to adsorption in the membrane pores. The flux decline was proved reversible; no membrane fouling occurred.

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