scholarly journals Numerical simulation of filtration performance in submerged membrane bioreactors: effect of particle packed structure

2017 ◽  
Vol 76 (9) ◽  
pp. 2503-2514 ◽  
Author(s):  
Zhidong Wang ◽  
Kuizu Su ◽  
Tong Shu ◽  
Weihong Wang
Keyword(s):  
Membrane Surface ◽  
Membrane Bioreactors ◽  
Navier Stokes ◽  
Permeate Flux ◽  
The Finite Element Method ◽  
Brinkman Equations ◽  
Filtration Performance ◽  
Cake Layer ◽  
Packed Structure ◽  
Cake Porosity

Abstract It is widely known that the accumulation of solid matter forming a cake layer on the membrane surface is one of the major limitations of the filtration performance in submerged membrane bioreactors (SMBR). This study is focused on the influence of the cake porosity of different particle microscopic packed structures on the filtration performance of hollow fiber systems. An integrated model based on the finite element method to simulate numerically the flow in an SMBR is presented. The model coupled the Navier–Stokes and Darcy Brinkman equations to simulate a complete filtration run. The cake growth took into consideration not only the deposition with local filtration velocity but also the effect of aeration scouring. A novel solution of mesh deformation was adopted to investigate transient cake growth along the fiber. Comparisons between simulations and experiments are in good agreement. The results show that a higher porosity particle packed structure causes non-uniform filtration and cake thickness but also higher permeate flux. Meanwhile, the proportion of cake resistance to total resistance increases with the decrease of porosity.

Influences of electroosmosis and electrophoresis on permeate flux and membrane fouling in submerged membrane bioreactors (SMBRs)

2016 ◽  
Vol 74 (3) ◽  
pp. 766-776 ◽  
Author(s):  
Secil Bayar ◽  
Ahmet Karagunduz ◽  
Bulent Keskinler
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Membrane Bioreactors ◽  
Polymeric Membrane ◽  
Soluble Microbial Products ◽  
Permeate Flux ◽  
Electrical Field ◽  
Cake Layer ◽  
Significant Process ◽  
Microbial Products

The objective of this study was to investigate the influences of electroosmosis (EO) and electrophoresis (EP) on the permeate flux in submerged membrane bioreactors. When a polymeric membrane is placed in between an anode and a cathode, both EO and EP occur simultaneously, causing enhancement in flux. Results showed that after 150 min of filtration, the permeate fluxes were 60, 115, 175 and 260 L/m2/h at 0, 30, 40 and 50 V, respectively. It was shown that the EO was linearly changing with increasing voltage, reaching up to 54 L/m2/h at 50 V. EP was found to be a significant process in removing soluble microbial products from the membrane surface, resulting in an increase in permeate flux as the filtration progressed. About 20-fold of smaller protein and carbohydrate concentrations were found in the cake layer when the electrical field (EF) was applied. However, the EF application promoted pore fouling, because of the calcium and magnesium scaling.

scholarly journals Unravelling colloid filter cake motions in membrane cleaning procedures

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Arne Lüken ◽  
John Linkhorst ◽  
Robin Fröhlingsdorf ◽  
Laura Lippert ◽  
Dirk Rommel ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Filter Cake ◽  
Membrane Surface ◽  
Cross Flow ◽  
Laser Scanning Confocal Microscopy ◽  
Scanning Confocal Microscopy ◽  
Filtration Performance ◽  
Dynamic Mobility ◽  
Cake Layer ◽  
Filter Cakes

AbstractThe filtration performance of soft colloid suspensions suffers from the agglomeration of the colloids on the membrane surface as filter cakes. Backflushing of fluid through the membrane and cross-flow flushing across the membrane are widely used methods to temporally remove the filter cake and restore the flux through the membrane. However, the phenomena occurring during the recovery of the filtration performance are not yet fully described. In this study, we filtrate poly(N-isopropylacrylamide) microgels and analyze the filter cake in terms of its composition and its dynamic mobility during removal using on-line laser scanning confocal microscopy. First, we observe uniform cake build-up that displays highly ordered and amorphous regions in the cake layer. Second, backflushing removes the cake in coherent pieces and their sizes depend on the previous cake build-up. And third, cross-flow flushing along the cake induces a pattern of longitudinal ridges on the cake surface, which depends on the cross-flow velocity and accelerates cake removal. These observations give insight into soft colloid filter cake arrangement and reveal the cake’s unique behaviour exposed to shear-stress.

Description of different effects of in-line coagulation upon semi-dead-end ultrafiltration

2003 ◽  
Vol 3 (5-6) ◽  
pp. 337-344 ◽  
Author(s):  
W. Doyen ◽  
R. Vandaele ◽  
B. Molenberghs ◽  
J. Cromphout ◽  
P. Bielen ◽  
...  
Keyword(s):  
Surface Water ◽  
Membrane Surface ◽  
Environmental Scanning Electron Microscopy ◽  
High Volume ◽  
High Water ◽  
Transmembrane Pressure ◽  
Water Recovery ◽  
Dead End ◽  
Cake Layer ◽  
Cake Porosity

This paper describes the results of research focussed on the different effects of in-line coagulation (FeCl3), towards the operation of semi-dead-end UF for drinking water and process water production starting from surface water. In this research, firstly the effects of the use of FeCl3 on the formed cake were studied, by both direct and indirect measurements. Using the ESEM technique (environmental scanning electron microscopy), which enables one to make pictures of wet samples, we observed that cake thickness was much higher upon use of FeCl3 (20 instead of 2 μm). As a result, the cake porosity was calculated to be much higher with than without coagulant use (93% instead of 37%). From the stability (nonincreasing) of the starting transmembrane pressure (TMP) in the successive filtration cycles, upon semidead-end operation, it was concluded that cake layer was less prone to adhere to the membrane surface when using coagulant. This is even more emphasized once the dosing is stopped, as a consequence the TMP rises very steeply under difficult circumstances, such as; high flux rates, high water recovery rates, and the use of membranes made from polymers with high adsorption properties. Secondly, indirect effects of the use of coagulant on filtration behaviour were investigated. Thus, it was found that TMP increase in the filtration cycle was much lower, due to depth filtration in the formed high-volume cake, and TMP was much more stable over a long time. These observations were in good agreement with found higher cake porosity. Moreover, it was observed that due to the use of a coagulant, the influences of membrane polymer nature and membrane structure disappeared, cleaning action could be postponed and cleaning aggressiveness could be lowered. In addition, water recovery and flux rate could be increased, and influence of seasonal water quality variations could be better faced. Finally, it was found that the treatment of surface water with high DOC content (e.g. 10 mg DOC/l) was enabled.

The Fluid Mechanics of Membrane Filtration

2007 ◽  
Author(s):  
Jack S. Hale ◽  
Alison Harris ◽  
Qilin Li ◽  
Brent C. Houchens
Keyword(s):  
Membrane Filtration ◽  
Concentration Polarization ◽  
Membrane Surface ◽  
Convective Transport ◽  
Contaminated Water ◽  
Permeate Flux ◽  
Large Pressure ◽  
Cake Layer ◽  
Large Pressure Gradient ◽  
Concentration Polarization Layer

Reverse osmosis and nanofiltration membranes remove colloids, macromolecules, salts, bacteria and even some viruses from water. In crossflow filtration, contaminated water is driven parallel to the membrane, and clean permeate passes through. A large pressure gradient exists across the membrane, with permeate flow rates two to three orders of magnitude smaller than that of the crossflow. Membrane filtration is hindered by two mechanisms, concentration polarization and caking. During filtration, the concentration of rejected particles increases near the membrane surface, forming a concentration polarization layer. Both diffusive and convective transport drive particles back into the bulk flow. However, the increase of the apparent viscosity in the concentration polarization layer hinders diffusion of particles back into the bulk and results in a small reduction in permeate flux. Depending on the number and type of particles present in the contaminated water, the concentration polarization will either reach a quasi-steady state or particles will begin to deposit onto the membrane. In the later case, a cake layer eventually forms on the membrane, significantly reducing the permeate flux. Contradictive theories suggest that the cake layer is either a porous solid or a very viscous (yield stress) fluid. New and refined models that shed light on these theories are presented.

scholarly journals Performance of an indigenous integrated slurry photocatalytic membrane reactor (PMR) on the removal of aqueous phenanthrene (PHE)

2018 ◽  
Vol 77 (11) ◽  
pp. 2642-2656 ◽  
Author(s):  
C. Nirmala Rani ◽  
S. Karthikeyan
Keyword(s):  
Membrane Fouling ◽  
Membrane Reactor ◽  
Membrane Surface ◽  
Continuous Process ◽  
Permeate Flux ◽  
Toc Removal ◽  
Recovery Potential ◽  
Cake Layer ◽  
Alkaline Conditions ◽  
Photocatalytic Membrane Reactor

Abstract In this study, a slurry photocatalytic membrane reactor (PMR) was developed and evaluated for the degradation of aqueous phenanthrene (PHE). During continuous process with a hydraulic retention time (HRT) of 140 min, the maximum PHE degradation and total organic carbon (TOC) removal efficiencies were found to be 97% and 79%, respectively. The reuse and recovery potential of TiO2 was studied with continuous recycling. The major intermediates during photodegradation of PHE were found to be phenanthrenequinone, phenanthenol and fluorine. This study also includes an investigation of membrane fouling caused by hydrophilic nano TiO2. The cake layer observed on the membrane surface was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive spectroscopy (EDS). In addition, the effect of operating parameters such as pH and permeate flux on membrane fouling were also investigated. Low permeate flux and alkaline conditions reduced membrane fouling.

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.

Factors causing PAC cake fouling in PAC–MF (powdered activated carbon-microfiltration) water treatment systems

2005 ◽  
Vol 51 (6-7) ◽  
pp. 231-240 ◽  
Author(s):  
P. Zhao ◽  
S. Takizawa ◽  
H. Katayama ◽  
S. Ohgaki
Keyword(s):  
Activated Carbon ◽  
Metal Ions ◽  
Membrane Surface ◽  
Pilot Scale ◽  
Powdered Activated Carbon ◽  
Raw Water ◽  
Permeate Flux ◽  
Void Space ◽  
High Concentration ◽  
Cake Layer

Two pilot-scale powdered activated carbon–microfiltration (PAC–MF) reactors were operated using river water pretreated by a biofilter. A high permeate flux (4 m/d) was maintained in two reactors with different particle sizes of PAC. High concentration (20 g/L) in the PAC adsorption zone demonstrated 60–80% of organic removal rates. Analysis on the PAC cake fouling demonstrated that attached metal ions play more important role than organic matter attached on PAC to the increase of PAC cake resistance. Effects of factors which may cause PAC cake fouling in PAC-MF process were investigated and evaluated by batch experiments, further revealing that small particulates and metal ions in raw water impose prominent influence on the PAC cake layer formation. Fe (II) precipitates after being oxidized to Fe (III) during PAC adsorption and thus Fe(III) colloids display more significant effect than other metal ions. At a high flux, PAC cake layer demonstrated a higher resistance with larger PAC due to association among colloids, metals and PAC particles, and easy migration of small particles in raw water into the void space in the PAC cake layer. Larger PAC possesses much more non-uniform particle size distribution and larger void space, making it easier for small colloids to migrate into the voids and for metal ions to associate with PAC particles by bridge effect, hence speeding up and intensifying the of PAC cake fouling on membrane surface.

scholarly journals Effect of operation paramaters on the filtration behavior in microfiltratration of TiO2 suspended

2021 ◽  
Vol 10 (1) ◽  
pp. 84-92
Author(s):  
Chinh Pham Duc ◽  
Thuy Nguyen Thi Thu ◽  
Tham Bui Thi ◽  
Quang Phan Ngoc ◽  
Cuong Pham Manh ◽  
...  
Keyword(s):  
Ph Value ◽  
Complete System ◽  
Membrane Surface ◽  
Experimental System ◽  
Transmembrane Pressure ◽  
Permeate Flux ◽  
Cake Layer ◽  
Mechanical Separation ◽  
Set Up ◽  
The Relationship

The photocatalytic reaction using TiO2 suspended to degrade the residues of toxic organic compounds has been extensively studied, but the ultilization of this process has not been recorded on an industrial scale. One of the primary reasons is the separation of TiO2 catalyst from the treated solution mixture. Conventional mechanical separation methods such as centrifugation, flocculation-deposition do not allow for thorough separation and catalytic reuse, whereas the microfiltration / ultrafiltration membrane process has been demonstrated to be capable of composting isolates very suspended particles. Accordingly, in this study, an experimental system separating TiO2-P25 suspension by microfiltration membrane 0.2 µm on laboratory scale was set up. Effects of operating factors: TiO2 concentration, pH value, transmembrane pressure and crosss flow velocity were investigated. Result shown that TiO2 concentration greater than 1 g / l will fundamentally diminish the permeate flux, futhermore, in the transmembrane  pressure differential (∆P) fluctuating from 0.3 to 1.2 bar, the relationship between J and ∆P is a linear relationship. In addition, the study likewise shown that the formation of the cake layer (scale) on the membrane surface is the fundamental driver of the permeate flux degradation over time. These results are the basis for integrating membrane and photocatalytic processes into a complete system for degradation toxic organic compound residues.

Membrane fouling control through aggregate design and trans-membrane pressure selection

2002 ◽  
Vol 2 (5-6) ◽  
pp. 337-343 ◽  
Author(s):  
S.A. Lee ◽  
T.D. Waite ◽  
A.G. Fane ◽  
R. Amal
Keyword(s):  
Fractal Dimension ◽  
Membrane Fouling ◽  
Size Dependence ◽  
Operating Conditions ◽  
Size Analysis ◽  
Permeate Flux ◽  
Cake Layer ◽  
Cake Porosity ◽  
The Impact ◽  
Highly Porous

Treatment of waters and wastewaters by microfiltration (MF) requires the addition of chemical coagulants to enhance the removal of dissolved substances. Under these conditions the feed to the MF contains flocculated particulates which must be retained by the membrane. While an extensive knowledge base on the effect of dispersed particles on membrane cake formation and fouling exists, much less information is available on the impact of aggregates on cake characteristics. Results of impact of the size and structure (as characterized by the fractal dimension) of particulate aggregates on microfiltration membrane fouling are in qualitative agreement with a simple model based on the Carman-Kozeny equation. Larger flocs form a cake with large inter-floc porosity which results in a significantly higher permeate flux than achieved for smaller flocs. Concomitantly, looser flocs (of low fractal dimension) are likely to form a cake that has higher intra-floc voidage thus flux is higher than a cake made of compact flocs of similar size. Analysis of cake compression indicates that compressibility is strongly influenced by trans-membrane pressure (TMP). The placement of highly porous aggregates onto the membrane results in formation of a highly porous cake layer provided a low TMP is maintained. Rapid compression of the cake occurs at higher TMPs as shown by the significantly lower porosity of the cake. Under high TMP conditions, the cake porosity exhibits a strong size dependence with larger floc sizes yielding higher porosities. This result possibly indicates formation of relatively impermeable assemblages (as a result of significant compaction) with flux controlled by inter-aggregate flow, i.e. flow around compressed flocs. In comparison, the marked lack of size dependence of porosity at low TMP suggests that permeate flux is dominated by flow through (rather than around) the highly permeable flocs. These results suggest that it should be possible to control both operating conditions (such as TMP) and floc characteristics such that high permeate flux at a given TMP or low cake resistance at a fixed flux is achievable.

Novel Spacer Design Using Topology Optimization in a Reverse Osmosis Channel

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Seungjae Oh ◽  
Semyung Wang ◽  
Minkyu Park ◽  
Joon Ha Kim
Keyword(s):  
Topology Optimization ◽  
Reverse Osmosis ◽  
Membrane Surface ◽  
Navier Stokes ◽  
Permeate Flux ◽  
Membrane Channel ◽  
Reference Models ◽  
Membrane Surfaces ◽  
Ro Membrane ◽  
And Performance

The objective of this study is to design spacers using topology optimization in a two-dimensional (2D) crossflow reverse osmosis (RO) membrane channel in order to improve the performance of RO processes. This study is the first attempt to apply topology optimization to designing spacers in a RO membrane channel. The performance was evaluated based on the quantity of permeate flux penetrating both the upper and lower membrane surfaces. Here, Navier–Stokes and convection-diffusion equations were employed to calculate the permeate flux. The nine reference models, consisting of combinations of circle, rectangle, and triangle shapes and zig-zag, cavity, and submerged spacer configurations were then simulated using finite element method so that the performance of the model designed by topology optimization could be compared to the reference models. As a result of topology optimization with the allowable pressure drop changes in the channel, characteristics required of the spacer design were determined. The spacer design based on topology optimization was then simplified to consider manufacturability and performance. When the simplified design was compared to the reference models, the new design displayed a better performance in terms of permeate flux and wall concentration at the membrane surface.

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