A.G. Fane

Nanyang Technological University, Tumasik, Singapore

Are you A.G. Fane?

Claim your profile

Publications (379)734.14 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Microfiltration (MF) and ultrafiltration (UF) involving colloidal suspensions are often involved in separations, concentration and clarification processes in the food and beverage as well as other industries. The increase in concentration near the membrane surface owing to concentration polarization can cause some part of a colloidal fouling layer to become metastable whereby it can undero a higher order phase transition to a more dense gel. This was confirmed via deadend filtration studies wherein the fouling layer thickness obtained from the transmembrane pressure (TMP) was compared with that determined directly via ultrasonic time-domain reflectometry (UTDR). Whereas entering this metastable state is thermodynamically driven, the transition from a colloidal suspension to a more dense gel is a rate or kinetically driven process. This phase transition is manifest by a marked rate of increase in the TMP that occurs after an filtration time that is dependent on the flux. A ‘threshold transition flux’ is identified below which the time required for the phase transition can be considerably delayed. Since removing this dense gel layer via conventional cleaning protocols is more difficult, determining an operating strategy whereby this transition to a more dense gel can be delayed is clearly of interest for the optimal operation of MF and UF processes. To this end the effects of crossflow velocity, flux, salinity and colloidal silica concentration on this metastability phenomenon are studied for a polyethersulfone UF membrane under crossflow and constant flux conditions. A lower crossflow velocity and higher flux, increased salinity and higher colloidal silica concentration decrease the time required for the transition to a dense gel.
    Journal of Membrane Science 06/2014; · 4.09 Impact Factor
  • Jin Zhou, Victor W-C Chang, Anthony G Fane
    [Show abstract] [Hide abstract]
    ABSTRACT: As concerns of natural resource depletion and environmental degradation caused by desalination increase, research studies of the environmental sustainability of desalination are growing in importance. Life Cycle Assessment (LCA) is an ISO standardized method and is widely applied to evaluate the environmental performance of desalination. This study reviews more than 30 desalination LCA studies since 2000s and identifies two major issues in need of improvement. The first is feasibility, covering three elements that support the implementation of the LCA to desalination, including accounting methods, supporting databases, and life cycle impact assessment approaches. The second is reliability, addressing three essential aspects that drive uncertainty in results, including the incompleteness of the system boundary, the unrepresentativeness of the database, and the omission of uncertainty analysis. This work can serve as a preliminary LCA reference for desalination specialists, but will also strengthen LCA as an effective method to evaluate the environment footprint of desalination alternatives.
    Water research. 05/2014; 61C:210-223.
  • Yuan Liao, Rong Wang, Anthony Gordon Fane
    [Show abstract] [Hide abstract]
    ABSTRACT: The practical application of membrane distillation (MD) for water purification is hindered by the absence of desirable membranes that can fulfill the special requirements of MD process. Compared to the membranes fabricated by other methods, nanofiber membranes produced by electrospinning are of great interest due to their high porosity, low tortuosity, large surface pore size and high surface hydrophobicity. However, the stable performance of the nanofiber membranes in MD process is still unsatisfactory. Inspired by the unique structure of lotus leaf, this study aimed to develop a strategy to construct superhydrophobic composite nanofiber membranes with robust superhydrophobicity and high porosity suitable for use in MD. The newly developed membrane consists of a superhydrophobic silica-PVDF composite selective skin formed on polyvinylidene fluoride (PVDF) porous nanofiber scaffold via electrospinning. This fabrication method could be easily scaled up due to its simple preparing procedures. The effects of silica diameter and concentration on membrane contact angle, sliding angle and MD performance were investigated thoroughly. For the first time, the direct contact membrane distillation (DCMD) tests demonstrate that the newly developed membranes are able to present stable high performance over 50 hours of testing time, and the superhydrophobic selective layer exhibits excellent durability in ultrasonic treatment and continuous DCMD test. It is believed that this novel design strategy has great potential for MD membrane fabrication.
    Environmental Science & Technology 05/2014; · 5.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Forward osmosis membrane bioreactors (FOMBR) provide high quality permeate, however the propensity for membrane biofouling in FOMBRs is unknown. Here, FOMBRs were operated under high and low aeration and the membrane-associated biofilms were characterized by confocal laser scanning microscopy (CLSM) and rRNA gene-tagged pyrosequencing. CLSM images revealed that there was little biofilm formed under high aeration, while thick biofilms were observed on the membranes operated under low aeration. The diversity and richness of bacterial and archaeal communities as assessed by pyrosequencing varied under high and low aeration. The composition of the bacterial suspended sludge communities and the sessile biomass on the membrane surface, as assessed by non-metric multidimensional scaling, was significantly different under high aeration, but was more similar under low aeration. SIMPER analysis indicated that Pseudomonas, Aeromonas and Fluviicola preferentially attached to the membrane. The results presented here provide a comprehensive understanding of membrane biofouling in FOMBRs, which is essential for the development of effective control strategies.
    Water Research 04/2014; 58C:141-151. · 4.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Backwashing of submerged hollow fiber membranes has been observed to have an unstable impact on the recovery of the membrane permeability. Modeling and experimental results in this study show that the effectiveness of fixed backwash cycles can decrease over time and reach a point at which the backwash effectiveness suddenly decreases. Evidence from transmembrane pressure (TMP) monitoring suggests that the sudden decrease in backwash efficiency occurs when the pressure on the permeate side of the membrane at the end of a backwash cycle does not reach the atmospheric pressure maintained on the feed side. The release of dissolved air on the permeate side of the membrane due to the pressure drop across the membrane was recognized as a major reason for reducing backwash effectiveness. The mathematical model predicts that the minimum backwash duration required to reverse the flow through the membrane by increasing the permeate-side pressure up to atmospheric pressure depends on the pressure at the beginning of the backwash, backwash flow rate, amount of air on the permeate side, membrane surface area, water viscosity, temperature, and the membrane and fouling resistances. These findings have implications for the design and operation of submerged membranes with backwash.
    Journal of Membrane Science 01/2014; 456:77–84. · 4.09 Impact Factor
  • Jia Wei Chew, William B. Krantz, Anthony G. Fane
    [Show abstract] [Hide abstract]
    ABSTRACT: Membrane distillation (MD) is a continuous process whereby a hot aqueous feed provides the latent heat to vaporize water that diffuses through a hydrophobic microporous membrane and condenses. MD is attractive for saline and wastewater treatment as well as concentrating heat-sensitive solutions such as fruit juices and biological fluids since it operates at moderate temperatures and atmospheric pressure, rejects particulates and nonvolatile solutes, uses non-selective membranes, and has low capital costs. However, MD and MD bioreactor (MDBR) performance is compromised by fouling. The effect of fouling layers with reasonably large pores (>50 nm) is reasonably well-understood and has been incorporated into MD models. However, the effect of fouling layers with very small pores or free volume (<50 nm) owing to macromolecular- and bio-fouling (MMBF) is not well-understood. While MMBF introduces an additional resistance to heat transfer, it can also reduce the vapor-pressure driving force. This latter effect is unique to MD fouled by MMBF. In this analysis the vapor pressure reduction has been incorporated into a model that indicates the large flux declines observed in prior studies can be explained by the vapor-pressure reduction associated with pore diameters ranging from 3.9 to 8.5 nm, which agree well with evapoporometry characterization of MMBF sludges. The predicted flux decline and temperature polarization coefficient indicate that the vapor-pressure reduction increases markedly for effective pore diameters less than 10 nm, but can be mitigated by increasing the thermal resistance of the membrane and by fabricating a dual-layer membrane for which the feed side is hydrophilic with relatively large pores.
    Journal of Membrane Science 01/2014; 456:66–76. · 4.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
    Journal of Membrane Science 01/2014; · 4.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The roles of Pseudomonas aeruginosa polysaccharides (Pel, Psl, alginate) in reverse osmosis (RO) membrane biofouling and nitric oxide (NO) induced dispersal were investigated. While mutants deficient in Psl formed significantly lower biofilm (total cell and polysaccharide) biovolumes than the PAO1 wild-type on glass surfaces, total cell biovolumes were similar during fouling of RO membranes. However, biofilms of the Psl deficient mutants exhibited a striated pattern, leaving large areas of membrane unfouled and contained up to 70% less polysaccharide and 24% less protein than the wild-type. Membranes fouled by the psl mutants exhibited a 69% reduction in the rate of biofouling (pressure rise over a given period), while the pel and alginate mutants were similar to the wild-type, suggesting functional differences in the polysaccharides. Overproduction of alginate by a PDO300 mutant increased the biofouling rate (59%) relative to wild-type, highlighting the ability of this polysaccharide to promote biofilm adherence and increase hydraulic resistance to permeate flow in an RO system. These results emphasize the importance of attachment specific polysaccharides for bacteria when fouling industrial RO membranes. When exposed to NO, dispersal of the PDO300 mutant biofilm was 25% lower than the wild-type, whilst dispersal of the alginate deficient mutant was 11% greater. Alginate thus appears to play an important role in NO induced dispersal of PAO1 biofilms.
    Journal of Membrane Science 01/2014; 466:161–172. · 4.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Membrane distillation (MD) technology is being extensively studied to address operational challenges such as undesired thermal efficiency and scaling phenomenon in recovering valuable solutes and minimizing brine disposal. This study has explored the working mechanisms of utilizing gas–liquid two-phase flow to enhance heat transfer and mitigate scaling formation in MD concentration process, based on the quantification of heat-transfer coefficients and local scaling-resistance associated with bubble size properties. With the aid of direct observation and statistical analysis on the bubble characteristics in a specially-designed direct contact MD (DCMD) module, it was found that the bubbles with small mean bubble size and narrow size distribution were preferred for creating even flow distribution, intensifying mixing and enhancing surface shear rate. Compared to non-bubbling DCMD, the heat-transfer coefficient and temperature polarization coefficient (TPC) reached up to 2.30- and 2.13-fold, respectively, at an optimal gas flowrate of 0.2 L min−1. With the theoretical expressions for local scaling resistance derived based on the resistance-in-series model, the relative permeation flux (Jw/o|t=t1/Jw/o|t=0) in non-bubbling MD was quantified and found to rapidly decline by 65% as the concentration process progressed, consistent with the increasing trend of the ratio of local scaling resistance to the overall resistance (rfl/rov). Fortunately, the introduction of gas bubbles has shown benefits for supersaturation brine concentrating MD process – remarkably decreased the local-scaling resistance due to bubble-intensified shear stress and enhanced hydrodynamics. Also, the total water removal for the brine concentration process was significantly improved by 131% and the discharged brine volume was reduced accordingly at appropriately selected gas flow rates. Nevertheless, at inappropriately high gas flowrates, high energy consumption and potential fiber breakage should be avoided.
    Journal of Membrane Science 01/2014; 470:60–69. · 4.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A comparative study of transverse and longitudinal vibrations of submerged hollow fibre membranes for fouling control was carried out in this paper. The same membrane module was adopted in the comparison, and the reactor geometry was identical. The orientation between the vibration and membrane fibre directions was the only difference between the two. The feed suspensions included both inorganic Bentonite and organic yeast suspensions. The results showed that transverse vibrations were generally more effective in terms of fouling reduction even at a very low vibration frequency of 1 Hz, which may be attributed to the separating boundary layers and the associated secondary flows around the cylindrical membrane fibres. The difference between the two orientations was very substantial in Bentonite suspensions, but less so in yeast suspensions due to the main membrane foulants of cell debris in the yeast components which caused the pore blockage of the membrane. A small degree of fibre looseness was found to further improve membrane performance with transverse vibrations in both Bentonite and yeast suspensions due to additional lateral fibre movement. The effect of packing density of the membrane bundle in transverse vibrations was also examined. The results showed that at larger vibration amplitudes, a high packing density of fibres can be operated with little membrane fouling, which indicated that the secondary flow generated could overcome the strong permeate flux competition within the bundle under vibrations. Finally, vibration relaxation was tested experimentally in half-on/off switching mode with the energy reduction due directly to the 50% stoppage. The results showed that a short relaxation time interval was generally more favourable for fouling reduction.
    Journal of Membrane Science 01/2014; 455:83–91. · 4.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The concept of a critical permeation flux for the onset of particle deposition in crossflow microfiltration (CFMF) is well-established. However, the critical flux is known to be a function of process parameters such as the particle size, bulk concentration and crossflow velocity. In the present study, the critical modified Peclet number (Pecrit) is explored instead as a generalized criterion for the onset of particle deposition that incorporates the effects of these process parameters as well as the axial position along the membrane. A proper determination of Pecrit requires an accurate prediction of the concentration polarization boundary layer thickness δc and shear-induced diffusion coefficient Ds. The classical Lévêque model is adapted to allow for the effect of the permeation flux on the velocity profile. Moreover, the assumptions of a constant concentration at the membrane surface cw and constant Ds that have been made in prior studies are relaxed in an improved numerical solution to the convective diffusion equation that is used to predict δc and Ds. The critical permeation flux is determined from particle deposition data taken for 6 and 10 μm latex spheres via Direct Observation Through the Membrane (DOTM) characterization. A constant value of Pecrit=4.00±0.08 is found to characterize the effects of particle diameter, bulk concentration and crossflow velocity as well as axial position on the onset of particle deposition.
    Journal of Membrane Science 01/2014; 457:128–138. · 4.09 Impact Factor
  • Xing Yang, Anthony G. Fane, Rong Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: This chapter provides a comprehensive introduction to the state-of-the-art of Membrane Distillation, including basic theoretical principles, system design configurations, technical advancements, limitations, and future prospects for water desalination. Focus will be on the historical perspectives of MD, process engineering aspects including membrane characteristics, module design, applications and cost evaluation. The technical requirements together with the benefits and limitations will also be addressed in terms of economic consideration and process engineering. It is expected to provide future prospects to implement the MD process industrialization as a promising desalination technique. Keywords: membrane distillation, desalination, mass and heat transfer, renewable energy, process engineering, water productivity cost
    01/2014: pages 373-424; , ISBN: 978-1-118-20852-6
  • GZ. Chen, YH. Lu, X. Yang, R. Wang, A G. Fane
    Industrial & Engineering Chemistry Research 01/2014; · 2.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Biofilm development in a spacer-filled reverse osmosis membrane channel can influence both trans-membrane pressure (TMP) and channel pressure drop (ΔPCH). While current pretreatment methods are unable to completely tackle the biofouling problem, more insights are required to provide strategies to minimize the problem. This study examined the role of operating parameters (i.e. flux and crossflow velocity) to minimize biofouling in RO processes. The experiments were conducted with a lab-scale high pressure flat sheet RO reactor where changes in pressure drop along the channel and across the membrane were measured. The impact of biofouling was measured at constant fluxes, where the TMP rise and ΔPCH rise and the biofoulant was quantified as biovolumes of live and dead bacteria on autopsied membrane and spacer samples by confocal laser scanning microscopy (CLSM). The results show that TMP rise increased exponentially with increasing flux, and decreased with increasing crossflow velocity. The channel pressure drop, ΔPCH, increased when either flux or crossflow velocity was increased, and was more dependent on crossflow. The biofoulant volume on the membrane increased with flux and was less dependent on crossflow. The biofoulant associated with the spacer was much less than on the membrane and relatively insensitive to flux or crossflow velocity. The TMP rise could be correlated with the estimated concentration of nutrient at the membrane surface, Cw,N, highlighting the combined roles of flux and crossflow velocity in solute concentration polarization. Previous TMP rise data could also be correlated to the estimated Cw,N values. This observation suggests a biofouling mitigation strategy by controlling both incoming nutrient concentration and operating conditions (flux and crossflow).
    Journal of Membrane Science 01/2014; 467:116–125. · 4.09 Impact Factor
  • Water Research. 01/2014; 58:141–151.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Among four membrane distillation (MD) configurations, direct contact MD (DCMD) and vacuum MD (VMD) exhibit attractive characteristics from different perspectives and have great potential in treating reverse osmosis (RO) brine. Aiming at establishing a quick approach to predict the key output parameters associated with MD module performance and process efficiency, Aspen plus was employed to conduct systematic evaluation for both DCMD and VMD. Due to the lack of built-in MD operation models in Aspen Plus, one dimensional transport models were developed and complied as user customized units to simulate the hollow fiber-based DCMD and VMD modules. The corresponding programming was coded in FORTRAN language. The mathematical models for DCMD and VMD were verified by comparing the simulations results with the experimental and literature data, respectively. By incorporating the boundary-layer effect into the newly-established transport models, steady-state simulations of the respective DCMD and VMD flowsheets were carried out. The results showed that the DCMD presented much lower process efficiency than VMD in terms of permeation flux and specific energy consumption per kg distillate generated, even though it is considered as the simplest and most commonly employed configuration. With the same module specifications and operating conditions at equivalent energy cost, the VMD system demonstrated a minimal 2.5-fold higher average vapor flux (e.g., water recovery capacity) when compared to DCMD. The fundamental difference between the two configurations was revealed through MD mass- and heat-transfer analysis. Based on simulated temperature profiles, it was found that the VMD configuration presented a much higher driving force (transmembrane temperature difference) and negligible conductive heat loss to the membrane, which is a promising feature for achieving high thermal efficiency.
    Journal of Membrane Science 01/2014; 464:127–139. · 4.09 Impact Factor
  • Jin Zhou, Victor W.-C. Chang, Anthony G. Fane
    Water Research. 01/2014; 61:210–223.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pore-size distribution determined by evapoporometry of unfouled (dark-shaded) and fouled (light-shaded) polyvinylidine fluoride (PVDF) hollow fiber membranes; fouling involved a constant flux of 70 l/m2 h, concentration of l.0 g/l of bentonite and 20 mg/l of humic acid, and employed a cycle consisting of 15 min of filtration followed by 2 min of backwashing during which the aeration rate was 0.0011 m/s; fouled membranes were observed after the 9th cycle; fouling is seen to cause a marked shift in the pore-size distribution towards smaller pores and a decrease in the average pore diameter from 34.6 nm to 22.5 nm owing to internal pore fouling.
    Journal of Membrane Science 01/2014; 470:334–345. · 4.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: a b s t r a c t Low-field bench-top nuclear magnetic resonance imaging (MRI) has been applied to investigate the hydrodynamics in novel hollow fiber modules with four different configurations of randomly-packed, spacer-knitted, curly and semi-curly fibers, specifically designed for the membrane distillation (MD) process. Imaging, spatially resolved velocity maps and propagators (probability distributions of displacement/velocity) were all acquired in the modules with flow in the shell side. The MRI data were correlated with overall module performance. The results have revealed that the curly configuration exhibited more significant transverse flow and hence enhanced mixing, compared to the randomly packed configuration; this was consistent with an enhanced MD performance in terms of permeation flux. Interestingly, the velocity maps of the spacer-knitted fiber design indicated a significant flow channeling in the center of the module, despite its enhanced MD performance. Fortunately, combined with further investigations on the localized velocity images of this configuration, the acquisition of propagators provided valuable information in revealing the existence of reduced stagnant regions and significant transverse flow at varied operating conditions, which indicated a better overall mixing and hence confirmed its module performance. & 2013 Elsevier B.V. All rights reserved.
    Journal of Membrane Science 01/2014; 451:46-54. · 4.09 Impact Factor
  • Journal of Membrane Science 01/2014; · 4.09 Impact Factor

Publication Stats

5k Citations
734.14 Total Impact Points

Institutions

  • 2005–2014
    • Nanyang Technological University
      • School of Civil and Environmental Engineering
      Tumasik, Singapore
    • Nanyang Normal University
      Nan-yang-shih, Henan Sheng, China
  • 2013
    • Universiti Tunku Abdul Rahman
      • Faculty of Engineering and Green Technology
      Kuala Lumpor, Kuala Lumpur, Malaysia
  • 2010–2011
    • Dalian University of Technology
      • School of Environmental and Biological Science and Technology
      Lü-ta-shih, Liaoning, China
    • Shanghai Jiao Tong University
      Shanghai, Shanghai Shi, China
  • 1981–2011
    • University of New South Wales
      • • School of Chemical Engineering
      • • ARC Centre for Functional Nanomaterials
      • • UNESCO Centre for Membrane Science and Technology
      • • School of Civil and Environmental Engineering
      • • School of Physics
      Kensington, New South Wales, Australia
  • 2003–2006
    • King Mongkut's University of Technology Thonburi
      • Department of Chemical Engineering
      Thon Buri, Bangkok, Thailand
    • University of Oxford
      • Department of Engineering Science
      Oxford, ENG, United Kingdom
    • Beijing University of Chemical Technology
      Peping, Beijing, China
  • 2004
    • University of Sydney
      • School of Chemical and Biomolecular Engineering
      Sydney, New South Wales, Australia
  • 1992
    • University of Colorado at Boulder
      Boulder, Colorado, United States