Role In Membrane Fouling Research Articles

Influence of Membrane Properties on Pineapple Wine Clarification and Fouling Behavior

The experiment was carried out to investigate the influence of membrane pore size and hydrophobicity on the quality of clarified pineapple wine and fouling characteristics, using stirred cell dead–end microfiltration. The test membranes were mixed cellulose acetate (MCE, pore size 0.45 and 0.22 μm), modified polyvinylidene fluoride (MPVDF, 0.22 μm) and polyethersulfone (PESF, 0.22 μm). It was found that all types of membrane successfully clarified the pineapple wine. The membrane pore size and hydrophobicity played an importance role in membrane fouling, both reversible and irreversible. Regarding the permeate flux and fouling, 0.45 μm MCE was the most suitable for pineapple wine clarification. However, intensive organoleptic test with pilot scale would be needed.

Interaction energy and competitive adsorption evaluation of different NOM fractions on aged membrane surfaces

Natural organic matter (NOM) plays a key role in membrane fouling, especially in irreversible fouling. Different PVDF membrane aging degrees lead to variations in the chemical/physical properties of membrane which further affect membrane permeability and fouling behavior. In the present work, the interaction energy between foulants and membranes with different ageing degrees was assessed by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, using bovine albumin serum (BSA), sodium alginate (SA) and humic acids (HA) as model foulants. Fluorescence labeling and confocal laser scanning microscopy (CLSM) was applied to characterize the distribution rule of binary foulants formed on membrane surfaces. The calculation of CLSM images via COMSTAT could quantify each foulant distribution in the fouling layer, which provides insights on combined fouling mechanisms. Results showed that membrane ageing modifies NOM fouling behaviors in according to the degree of ageing. Furthermore, filtration of the SA/BSA mixtures showed that BSA was first absorbed on the membrane surface in a competitive environment, which then plays a bridge role in promoting the SA to form a denser cake layer on the membrane. That is to say, different ageing degrees mainly affected the attachment of BSA to the membrane surface with regard to mixture of organics.

Experimental and Modeling Assessment of the Roles of Hydrophobicity and Zeta Potential in Chemically Modified Poly(ether sulfone) Membrane Fouling Kinetics

This study investigated the roles of hydrophobicity and zeta potential of polymer membranes and foulants on membrane fouling during filtration. A series of chemically modified poly(ether sulfone) (PES) membranes were used to evaluate filtration performance with bovine serum albumin (BSA) and humic acid (HA) employed as model foulants. Hydrophobicity and zeta potential of both membranes and foulants were measured and incorporated in the surface interaction energy calculation by the extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) theory analysis. Foulant deposition rate was then calculated based on particle transport equation and interaction energy. Membrane fouling rates, indicated by the decrease of permeate flux, were well correlated (R2 = 0.74–0.99) with the foulant deposition rates. This correlation indicates that both electrostatic interaction and hydrophobic interaction played decisive roles in membrane fouling. Our results have important implications for elucidation and prediction of the structure...

Role of pectin and haze particles in membrane fouling during cold microfiltration of apple cider

The role of pectin in membrane fouling during cold MF of apple cider was investigated. Clarified apple juice with four different concentrations of pectin was subjected to cold MF, at pore sizes above 0.45 μm. The experimental data shows that pectin plays a significant role in membrane fouling, and its fouling effect increased with increasing concentration. The association of pectin with polyphenols and proteins, which results in colloidal haze particles with low surface electrical charge, seems to be the major factor in fouling during cold MF of apple cider. Depectinization was beneficial to MF with pore sizes below 0.45 μm, for which fouling is dominated by cake layer formation. Depectinization had a negative effect on MF flux for pore sizes above 0.8 μm, since the size reduction of haze particles accentuated pore constriction and blockage, which dominate fouling in large pore MF. These findings have practical implications for the development of efficient, commercially viable, cold MF processes for minimally processed apple cider.

Characterization and Significance of Sub-Visible Particles and Colloids in a Submerged Anaerobic Membrane Bioreactor (SAnMBR).

The distribution, composition and morphological structure of subvisible particles and colloids (0.01-10 μm) in the supernatant of a lab-scale submerged anaerobic membrane bioreactor (SAnMBR), and their role in membrane fouling, was investigated. Photometric analysis showed that the supernatant and membrane foulants were dominated by particles and colloids (0.45-10 μm), which accounted for over 90% of the total organics (proteins and polysaccharides). Excitation-emission matrix (EEM) fluorescence spectra and monosaccharide analysis showed that these particles and colloids were rich in fluorescent proteins, rhamnose, ribose and arabinose, all of which could be related to cellular and extracellular substances. Fluorescence and scanning electron microscopy confirmed the presence of bacterial cells in/on the subvisible particles and colloids. The microparticles (5-10 μm) were primarily composed of Streptobacilli and/or filamentous bacteria in the form of microcolonies, while the submicrometer particles and colloids (1-5 μm and 100 kDa-1 μm) had more free/single cocci and bacilli. The ratio of live/dead cells varied in different size-fractions, and the particles (1-10 μm) contained more live cells compared with the colloids (100 kDa-1 μm). Our findings suggest that bacterial cells in/on the particles and colloids could have an important effect on fouling in SAnMBRs as they represent pioneering species attaching to membranes to form fouling layers/biofilm. Such insights reveal that previous foulant-characterization studies in MBRs tended to overestimate organic fouling, while the biofouling induced by these bacteria in/on the particles and colloids was overlooked.

Molecular Mechanisms of Ultrafiltration Membrane Fouling in Polymer-Flooding Wastewater Treatment: Role of Ions in Polymeric Fouling

Polymer (i.e., anionic polyacrylamide (APAM)) fouling of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes and its relationships to intermolecular interactions were investigated using atomic force microscopy (AFM). Distinct relations were obtained between the AFM force spectroscopy measurements and calculated fouling resistance over the concentration polarization layer (CPL) and gel layer (GL). The measured maximum adhesion forces (Fad,max) were closely correlated with the CPL resistance (Rp), and the proposed molecular packing property (largely based on the shape of AFM force spectroscopy curve) of the APAM chains was related to the GL resistance (Rg). Calcium ions (Ca(2+)) and sodium ions (Na(+)) caused more severe fouling. In the presence of Ca(2+), the large Rp corresponded to high foulant-foulant Fad,max, resulting in high flux loss. In addition, the Rg with Ca(2+) was minor, but the flux recovery rate after chemical cleaning was the lowest, indicating that Ca(2+) created more challenges in GL cleaning. With Na(+), the fouling behavior was complicated and concentration-dependent. The GL structures with Na(+), which might correspond to the proposed molecular packing states among APAM chains, played essential roles in membrane fouling and GL cleaning.

Long-term operation of biological activated carbon pre-treatment for microfiltration of secondary effluent: Correlation between the organic foulants and fouling potential

The impact of long-term (>2 years) biological activated carbon (BAC) treatment for mitigating organic fouling in the microfiltration of biologically treated secondary effluent was investigated. Correlation between the organic constituents and hydraulic filtration resistance was investigated to identify the major components responsible for fouling. Over two years operation, the removal efficiency for dissolved organic carbon (DOC) by the BAC treatment was fairly consistent (30 ± 3%), although the reduction in UVA254 gradually decreased from 56 to 34%. BAC treatment effectively decreased the organic foulants in the effluent and so contributed to the mitigation of membrane fouling as shown by reduction in the unified membrane fouling index (UMFI). BAC consistently removed biopolymers whereas the removal of humic substances decreased from 52 to 25% after two years of BAC operation, and thus led to a gradual decrease in UMFI reduction efficiency from 78 to 43%. This was due to gradual reduction in adsorption capacity of the activated carbon as confirmed by analysis of its pore size distribution. Hence humics also played an important role in membrane fouling. However, there was a good correlation between protein and carbohydrate contents with hydraulically reversible and irreversible filtration resistance, compared with UVA254, turbidity and DOC. Although the mitigation of membrane fouling decreased over time, this study demonstrated that the long-term use of BAC pre-treatment of biologically treated secondary effluent prior to microfiltration has potential to reduce the need for frequent chemical cleaning and so increase membrane life span.

Influence of COD:N ratio on sludge properties and their role in membrane fouling of a submerged membrane bioreactor

The effect of COD:N ratio on sludge properties and their role in membrane fouling were examined using a well-controlled aerobic membrane bioreactor receiving a synthetic high strength wastewater containing glucose. Membrane performance was improved with an increase in the COD/N ratio (100:5–100:1.8) (i.e. reduced N dosage). Surface analysis of sludge by X-ray photoelectron spectroscopy (XPS) indicates significant differences in surface concentrations of elements C, O and N that were observed under different COD/N ratios, implying changes in the composition of extracellular polymeric substances (EPS). Fourier transform-infrared spectroscopy (FTIR) revealed a unique characteristic peak (CO bonds) at 1735 cm−1 under nitrogen limitation conditions. Total EPS decreased with an increase in COD/N ratio, corresponding to a decrease in the proteins (PN) to carbohydrates (CH) ratio in EPS. There were no significant differences in the total soluble microbial products (SMPs) but the ratio of PN/CH in SMPs decreased with an increase in COD/N ratios. The results suggest that EPS and SMP composition and the presence of a small quantity of filamentous microorganisms played an important role in controlling membrane fouling.

Fouling analysis of membrane bioreactor treating antibiotic production wastewater at different hydraulic retention times.

Membrane fouling, including foulants and factors, was investigated during hydraulic retention time (HRT) optimization of a membrane bioreactor (MBR) that treated wastewater from the production of antibiotics. The results showed that HRT played an important role in membrane fouling. Trans-membrane pressure (TMP), membrane flux, and resistance were stable at -6kPa, 76Lm-2h-1bar-1, and 4.5 × 1012m-1 when HRT was at 60, 48, and 36h, respectively. Using Fourier transform infrared spectroscopy, foulants were identified as carbohydrates and proteins, which correlated with effluent organic matter and effluent chemical oxygen demand (COD) compounds. Therefore, membrane fouling trends would benefit from low supernatant COD (378mgL-1) and a low membrane removal rate (26%) at a HRT of 36h. Serious membrane fouling at 72 and 24h was related to soluble microbial products and extracellular polymeric substances in mixed liquor, respectively. Based on the TMP decrease and flux recovery after physical and chemical cleaning, irremovable fouling aggravation was related to extracellular polymeric substances' increase and soluble microbial products' decrease. According to changes in the specific oxygen uptake rate (SOUR) and mixed liquor suspended solids (MLSSs) during HRT optimization in this study, antibiotic production wastewater largely inhibited MLSS growth, which only increased from 4.5 to 5.0gL-1 when HRT was decreased from 72 to 24h, but did not limit sludge activity. The results of a principal component analysis highlighted both proteins and carbohydrates in extracellular polymeric substances as the primary foulants. Membrane fouling associated with the first principal component was positively related to extracellular polymeric substances and negatively related to soluble microbial products. Principal component 2 was primarily related to proteins in the influent. Additional membrane fouling factors included biomass characteristics, operational conditions, and feed characteristics.

Organic fouling in forward osmosis (FO): Membrane flux behavior and foulant quantification

Forward osmosis (FO) is an emerging membrane technology with potential applications in desalination and wastewater reclamation. The osmotic pressure gradient across the FO membrane is used to generate water flux. In this study, flux performance and foulant deposition on the FO membrane were systematically investigated with a co-current cross-flow membrane system. Sodium alginate (SA), bovine serum albumin (BSA) and tannic acid (TA) were used as model foulants. Organics adsorbed on the membrane were peeled off via oscillation and characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). When an initial flux of 8.42 L/m2h was applied, both flux reduction and foulant deposition were slight for the feed solution containing BSA and TA. In comparison, flux reduction and foulant deposition were much more severe for the feed solution containing SA, as a distinct SA cake-layer was formed on the membrane surface and played a crucial role in membrane fouling. In addition, as the initial SA concentration increased in FS, the thickness of the cake-layer increased remarkably, and the membrane fouling became more severe.

Effects of macro-porous anion exchange and coagulation treatment on organic removal and membrane fouling reduction in water treatment

Macro-porous anion exchange, coagulation and their combination were used as pretreatment for microfiltration, and their effects on organic removal and membrane fouling reduction were evaluated. The experimental results showed that resin was effective in removing organics of medium and small molecular weight (MW), especially those of medium MW of UV absorbance, but was ineffective in removing organics with large MW. Using resin alone as a pretreatment removed organics effectively but was limited in its reduction of membrane fouling. With the combination of coagulation and resin as a pretreatment for microfiltration, not only were organics removed effectively, but membrane fouling was also reduced. Analysis of membrane surface with scanning electron microscopy (SEM), atomic force microscopy (AFM) and combined results of behaviors of MW distribution and flux indicated that biopolymer plays a key role in membrane fouling, and coagulation could remove this part of organics. Integrated coagulation and resin pretreatment by filtration columns were suggested for use in surface water prior to membrane filtration.

Identification of the fouling-caused foulants with different pretreatments during ultrafiltration in polluted raw water

Different pretreatments, including coagulation, adsorption, and biofiltration, were used to identify the useful pretreatment for the ultrafiltration of polluted raw water. The following prefiltration investigation was conducted to identify foulants that were responsible for membrane fouling. Organic removal and particle size distribution of different pretreated samples were measured. The results indicated that the concentration of organic matter was not the critical factor that determined the extent of flux decline. The turbidity relevant materials, such as colloids and particles, were supposed to be important fouling-caused substances, and the particle size distribution also had a significant influence on flux decline. Moreover, the fouling resistance of different prefiltrated samples showed that foulants sized over the membrane pore size caused the main part of the membrane fouling in raw water. Component analysis demonstrated that protein-like substances played a crucial role in membrane fouling; however, humic-like substances led to a weak membrane fouling.

Analysis of the major particle-size based foulants responsible for ultrafiltration membrane fouling in polluted raw water

This paper focused on the major particle-size based foulants responsible for membrane fouling of ultrafiltration in simulated surface water polluted by sewage discharge. The experiment was conducted with a sequential filtration process, pre-filtration steps removed specific foulants (1.2μm, 0.45μm, 100kDa and 10kDa) from raw water with different membranes, and followed filtration tests were performed to investigate the fouling caused by remaining foulants. Flux decline and specific fouling resistance of different fractioned substances were compared to identify the particle-size based foulants most responsible for membrane fouling. The normalized flux decline showed that foulants over 1.2μm had limited influence on flux decline, but that the 100kDa–0.45μm fraction contributed a significant part. Results of specific fouling resistance revealed that the 100kDa–0.45μm fraction caused higher fouling resistance than other fractions with the same quality of organic matter, and this fraction was confirmed to be most closely related to protein-like substances. Component analysis demonstrated that protein-like substances played a crucial role in membrane fouling, whereas humic-like substances were of minor relevance. Standard blocking and cake filtration were major mechanisms of membrane fouling caused by pre-filtered water, independent of the pore size of fractionation membranes.

Effects of EPS on membrane fouling in a hybrid membrane bioreactor for municipal wastewater treatment

A pilot-scale hybrid membrane bioreactor (HMBR) for real municipal wastewater treatment was developed by adding biofilm carriers into a conventional membrane bioreactor, distribution and dynamic changes of the extracellular polymeric substances (EPS) and their roles in membrane fouling were investigated. The results showed that the concentrations of loosely bond EPS (LB-EPS) and tightly bond EPS (TB-EPS) in activated sludge, carrier biofilm and sludge cake layer have been increased significantly with the running time of HMBR, during operation of the HMBR, EPS demonstrated positive correlations with membrane fouling. Compared to TB-EPS, LB-EPS showed more significant correlations with sludge physical properties and specific resistance to filtration (SRF) in HMBR, and thus demonstrated that LP-EPS have a stronger potential of fouling than TB-EPS. It was also found that a lower organic loading in HMBR could result a significant increase in EPS concentration, which would in turn influence membrane fouling in HMBR. This critical investigation would contribute towards a better understanding of the behavior, composition and fouling potential of EPS in HMBR operation.

Characterization of algal organic matters of Microcystis aeruginosa: Biodegradability, DBP formation and membrane fouling potential

Algal organic matters (AOM), including extracellular organic matters (EOM) and intracellular organic matters (IOM), were comprehensively studied in terms of their biodegradability, disinfection byproduct (DBP) formation potentials and membrane fouling. EOM and IOM were fractionated into hydrophobic (HP), transphilic (TP) and hydrophilic (HL) constituents. The HP, TP and HL fractions of EOM and IOM were highly biodegradable with BDOC/DOC ranging from 52.5% to 67.4% and the DBP formation potentials followed the order of HP > TP > HL, except of IOM-HL. Biodegradable process proved very effective in removing the DBP formation potentials. Moreover, the AOM characteristics were also evaluated during ultrafiltration (UF) treatment. Results demonstrated that UF favourably remove DOC and DBP formation potential of IOM than those of EOM. And the HL constituents played a more important role in membrane fouling than HP and TP. The UF foulants exhibited higher BDOC/DOC than AOM, suggesting EOM and IOM might enhance biofouling because more biodegradable proteins and polysaccharides were found in membrane foulants. Therefore, appropriate biological treatment, ultrafiltration, or combination of the both are potential options to address these algae-caused water quality issues.

Insights into membrane fouling of a side-stream ceramic membrane reactor for phenol hydroxylation over ultrafine TS-1

A side-stream ceramic membrane reactor was established for continuous phenol hydroxylation to dihydroxybenzene including catechol and hydroquinone over ultrafine titanium silicalites-1 (TS-1) catalysts with H2O2 as the oxidant. The membrane fouling mechanisms were investigated in detail by designing a series of filtration experiments based on the gas chromatography/mass spectrometry (GC/MS) analysis of the reaction mixtures. The field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) were used to reveal the surface morphology and chemical nature of the fouled membranes. It is found that the reactant (phenol) and the target products (catechol and hydroquinone) have little influence on membrane fouling, but the overoxidation by-products of target products, such as p-benzoquinone, play an important role in membrane fouling. The filter cake formed on the membrane surface composed of the TS-1 particles and the overoxidation by-products is the main reason of membrane fouling. An efficient cleaning strategy of fouled membrane was also proposed, which leads to an over 95% recovery of pure water flux of the fouled membranes.

Effect of upflow velocity on the effluent membrane fouling potential in membrane coupled upflow anaerobic sludge blanket reactors

This study investigated the effect of upflow velocity (Vup) on biological removal efficiency and effluent filterability in a laboratory scale upflow anaerobic sludge blanket (UASB) reactor. Upflow velocities of 1.2, 0.6 and 1.2m/h were applied in three successive stages over a total operation period of 116 days. Filterability tests were carried out during each stage in order to assess the effect of Vup on subsequent membrane performance. Results indicated a significant impact of Vup on both biological performance and physicochemical effluent characteristics. The observed differences in protein/carbohydrate ratio and particle size distribution (PSD), which play important roles in membrane fouling, lead to the hypothesis that Vup is a critical parameter for effluent filterability in membrane coupled UASB reactors. Results showed that filterability of the effluent during the operation at 0.6m/h was better than that during the operation at 1.2m/h.

Identification of key factors affecting the organic fouling on low-pressure ultrafiltration membranes

The fouling behavior of the hollow fiber ultrafiltration (UF) membrane by the mixtures of dissolved organic matters (DOMs) has been systematically investigated. The organic foulants included humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA), which represented humic substances, proteins and polysaccharides, respectively. According to the experimental results, the filtration process of organic mixtures could be divided into a fast fouling stage and a slow fouling stage no matter what mixture was used. Scanning electronic microscopy (SEM) and the attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis of the surface of the fouled membranes revealed a significant difference in the structure of fouling layer, which may be attributed to the different deposition rates of the organics. More importantly, the molecular weight of DOMs, solution zeta potential (ZP) and particle size were examined in order to identify the key factors contributing to the fouling behavior. A strong correlation was found between fouling resistance and the content of small molecules in DOMs and solution zeta potential based on statistical analysis. Both factors played significant roles in membrane fouling. A more serious fouling could be observed with a higher proportion of small molecules or a more negative charge density of solution. Furthermore, the normalization data indicated that the effect of small molecule on membrane fouling was more important compared to the ZP of the solution.

Performance of Membrane Bioreactor (MBR) in High Phosphate Wastewater

This study presents the performance of membrane bioreactor in treating high phosphate wastewater. The laboratory scale MBR was operated at permeate flux of 25 L/m2.h with a hollow fiber membrane (polypropylene, approx. pore size 0.01 - 0.2 μm) at hydraulic retention time (HRT) of 12 hrs. Scanning electron microscopy (SEM) and energy diffusive X-ray (EDX) analyzer were used to characterize the membrane foulants. Results showed that the removal efficiencies of COD, TSS, NH3-N and PO4 3- were 93, 98, 80 and 30% respectively. On average 91% of influent soluble microbial products (SMP) were eliminated, with the eliminations of polysaccharides mostly above 80%. The main fouling resistance was cake resistance. It should be noted that SMP were found in major portions of mixed liquor that played a relatively significant role in membrane fouling. SEM and EDX analyses indicated that the foulants covering the membrane surfaces comprises not only organic substances but also inorganic elements including Mg, Ca, Al, K and P.

Potential Foulants and Fouling Indicators in MBRs: A Critical Review

Membrane fouling is one of the major obstacles for wide applications of MBRs. Over the past decade, the behaviors of colloidal and soluble substances have attracted much attention, and intensive efforts have been dedicated to the clarification of their role in membrane fouling. However, to date, the conclusions are often different and even controversial. The review is attempted to clarify their interrelations and to eliminate some confusions by reviewing the recent literature. The similarities and differences of those potential foulants are analyzed through comparing definitions, extraction methods, fouling indicators, and fouling behaviors. The implications of future research directions are also discussed in this paper.