The relationship between critical flux and fibre movement induced by bubbling in a submerged hollow fibre system

2005 ◽  
Vol 51 (6-7) ◽  
pp. 115-122 ◽  
Author(s):  
F. Wicaksana ◽  
A.G. Fan ◽  
V. Chen
Keyword(s):  
Membrane Fouling ◽  
Hollow Fibre ◽  
Transmembrane Pressure ◽  
Feed Concentration ◽  
Critical Flux ◽  
Improved Performance ◽  
Qualitative Relationship ◽  
The Relationship ◽  
Mechanical Movement ◽  
Fibre Characteristics

Bubbling has been used to enhance various processes. In this paper we deal with the effect of bubbling on submerged hollow fibre membranes, where bubbling is applied to prevent severe membrane fouling. Previous work with submerged hollow fibres has observed that significant fibre movement can be induced by bubbling and that there is a qualitative relationship between fibre movement and filtration performance. Therefore, the aim of the present research has been to analyse the link between bubbling, fibre movement and critical flux, identified as the flux at which the transmembrane pressure (TMP) starts to rise. Tests were performed on vertical isolated fibres with a model feed of yeast suspension. The fibres were subject to steady bubbling from below. The parameters of interest were the fibre characteristics, such as tightness, diameter and length, as well as feed concentration. The results confirmed that the critical fluxes are affected by the fibre characteristics and feed concentration. Higher critical flux values can be achieved by using loose fibres, smaller diameters and longer fibres. The enhancement is partially linked to fibre movement and this is confirmed by improved performance when fibres are subject to mechanical movement in the absence of bubbling.

Monitoring of transparent exopolymer particles (TEP) in a membrane bioreactor (MBR) and correlation with other fouling indicators

2008 ◽  
Vol 58 (10) ◽  
pp. 1903-1909 ◽  
Author(s):  
T. de la Torre ◽  
B. Lesjean ◽  
A. Drews ◽  
M. Kraume
Keyword(s):  
Linear Correlation ◽  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Systems ◽  
Transparent Exopolymer Particles ◽  
Critical Flux ◽  
Capillary Suction ◽  
Acidic Fraction ◽  
The Relationship

The occurrence of Transparent Exopolymer Particles (TEP), an acidic fraction of polysaccharides, was monitored for more than six months in the activated sludge of three MBR units, and the relationship between TEP and other fouling indicators was studied. These compounds consist mainly of exopolysaccharides of a sticky nature, a characteristic which makes them a group of interesting substances in processes like sedimentation, flocculation and membrane fouling. The relationship between capillary suction time (CST) and polysaccharides (PS) was linear for the three tested sludges, although the correlation with TEP concentrations was stronger. A slight linear correlation of both TEP and PS was found with the critical flux (CF) measured with a small filtration test cell, which was submerged in the membrane tank to assess the filterability performance of the sludge in situ. However, the correlation CF-PS was clearer. The relationship between TEP, polysaccharides and sludge filterability highlights the potential of this parameter for the monitoring of membrane systems.

Effects of feed concentration and transmembrane pressure on membrane fouling in Cd2+ removal by micellar-enhanced ultrafiltration

Desalination ◽  
2012 ◽  
Vol 294 ◽  
pp. 67-73 ◽  
Author(s):  
Jin-Hui Huang ◽  
Liang-Jing Shi ◽  
Guang-Ming Zeng ◽  
Xue Li ◽  
Song-Bao He ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Transmembrane Pressure ◽  
Feed Concentration ◽  
Micellar Enhanced Ultrafiltration

Analysis of nanoporous membrane fouling relying on experimental observation and theoretical model for landfill leachate treatment

2015 ◽  
Vol 73 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Mohsen Jahanshahi ◽  
Majid Peyravi ◽  
Nader Shafaei ◽  
Hatef Mirani
Keyword(s):  
Landfill Leachate ◽  
Membrane Fouling ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Operating Pressure ◽  
Feed Concentration ◽  
Leachate Treatment ◽  
Nanoporous Membrane ◽  
Flux Decline ◽  
Pore Blockage

This paper is focused on the fouling behaviour of the ultrafiltration membrane for landfill leachate treatment. Natural organic matter fouling is considered a critical factor controlling the membrane performance. In this regard, the polyethersulphone nanoporous membrane was fabricated by phase inversion. In order to investigate the effects of operating conditions on fouling, landfilled leachate treatment was done at different transmembrane pressure and feed concentration. At high concentration of landfill leachate, the effect of operating pressure can be negligible. The maximum amount of RFR was 0.961 for raw landfill leachate. Flux decline data were also obtained for the filtration of landfill leachate. The rates of flux decline drastically dropped to about 46–48% of the initial values in the first 30 minutes of the experiment at all the examined pressures. The data were also analyzed using a model in order to provide explanations for simultaneous pore blockage and cake formation. The model showed very good agreement with the data for all transmembrane pressures and feed concentrations. The initial fouling due to pore blockage is related to the feed concentration at constant pressure, so by diluting the feed concentration, the effect of pore blocking was increased.

Comparative investigation on the impact of polymeric substances on membrane fouling during sub-critical and critical flux operation of a municipal membrane bioreactor

2008 ◽  
Vol 58 (9) ◽  
pp. 1849-1855 ◽  
Author(s):  
S. Lyko ◽  
T. Wintgens ◽  
T. Melin
Keyword(s):  
Membrane Fouling ◽  
Pilot Scale ◽  
Comparative Investigation ◽  
Hollow Fibre ◽  
Size Exclusion ◽  
Dominant Factor ◽  
Permeate Flux ◽  
Critical Flux ◽  
Operational Conditions ◽  
The Impact

Soluble organic macromolecules are ubiquitous in activated sludge supernatant. For the operation of membrane bioreactors (MBR) this group of substances is considered as the dominant factor causing severe membrane fouling due to the concentration polarisation phenomenon. The well established critical flux concept for the characterisation of membrane bioreactor's operation limits is based on filtration data only. As there is an cause-and-effect relation between the partial retention of organic compounds and the limited flux according the critical flux concept the aim of this study was to draw a comparison between different permeate fluxes on the retention of organic macromolecules. Thus, a municipal pilot-scale MBR with three capillary hollow fibre membrane modules was operated in sub critical, critical and supercritical flux mode, respectively and the retention of macromolecules was quantified by size exclusion chromatography. Three permeate extraction pumps allow a simultaneous operation with different operational conditions for each membrane module and proved the crucial impact of permeate flux on the fouling rate. The interchange of these conditions gave evidence of an optimised start-up procedure for MBRs characterised by higher permeate fluxes. An increased flux causes both a higher retention of soluble macromolecules and subsequent a higher fouling rate.

Influence of feed concentration and transmembrane pressure on membrane fouling and effect of hydraulic flushing on the performance of ultrafiltration

Desalination ◽  
2014 ◽  
Vol 335 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Jinhui Huang ◽  
Liuxia Liu ◽  
Guangming Zeng ◽  
Xue Li, ◽  
Lei Peng ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Transmembrane Pressure ◽  
Feed Concentration

Improvement of microfiltration performance in water treatment: is critical flux a viable solution?

2000 ◽  
Vol 41 (10-11) ◽  
pp. 309-315 ◽  
Author(s):  
S. Vigneswaran ◽  
D.Y. Kwon ◽  
H.H. Ngo ◽  
J.Y. Hu
Keyword(s):  
Membrane Fouling ◽  
Particle Deposition ◽  
Material Balance ◽  
Transmembrane Pressure ◽  
Operational Mode ◽  
Permeate Flux ◽  
Critical Flux ◽  
Viable Solution ◽  
Crossflow Microfiltration

In this study, three definitions for critical flux were introduced based on the crossflow microfiltration (CFMF) experiments conducted under an operational mode of constant permeate flux. The critical flux based on material balance was calculated from the rate of particles deposition. The highest permeate flux results in no particle deposition being taken at the critical flux. The second definition was based on the increase in transmembrane pressure (TMP). The critical flux based on the TMP increase is the flux below which the membrane fouling does not occur. The third definition was based on the direct observation of particles deposition through microscope. Detailed experiments were conducted with synthetic suspension of different sizes of latex particles. Long term experiments conducted with polydispersed kaolin clay suspension indicated that the critical flux based on material balance concept is more realistic in field conditions.

A cost optimization study of flux and fouling rate for UF in the water industry

2008 ◽  
Vol 8 (1) ◽  
pp. 113-120 ◽  
Author(s):  
G. K. Pearce
Keyword(s):  
Membrane Fouling ◽  
Cost Optimization ◽  
Plant Size ◽  
Operating Pressure ◽  
High Flux ◽  
Chemical Cleaning ◽  
Critical Flux ◽  
Membrane Area ◽  
Optimization Study ◽  
The Relationship

Designing a commercial UF/MF system is an exercise in compromise. Selecting a high flux reduces capex by minimizing the membrane area required, but increases operating costs due to the increased chemical cleaning frequency, higher waste disposal volumes, and higher operating pressure. Most commercial systems are designed to run at fluxes significantly above the critical flux, so a degree of fouling and a reliance on chemical cleaning is inherent to the design. This paper examines the relationship between flux and membrane fouling rate through a review of experimental field data. The analysis shows that fouling rate increases exponentially with flux, with a function dependent upon the characteristics of the feed. The paper then presents the results of a cost optimization study in which Total Water Cost (TWC) is evaluated as a function of feed source and plant size for different CIP cleaning frequencies. The minimum TWC occurs in all cases for CIP frequencies of between 1/week and 1/month. Smaller plants with low fouling feeds have an optimum near 1 CIP/week using a relatively high flux design. In contrast, feeds with higher fouling propensity, and medium or large plant sizes have a TWC optimum close to 1 CIP/month, and should use a lower design flux. It is suggested that the flux corresponding to the TWC optimum should be designated the sustainable flux.

The Relationship between Critical Flux and Membrane Fouling

2014 ◽  
Vol 535 ◽  
pp. 675-678
Author(s):  
Wei Ying Li ◽  
Jun Peng Zhang ◽  
Wen Ming Li
Keyword(s):  
Membrane Fouling ◽  
Sand Filtration ◽  
Short Term ◽  
Step Method ◽  
Critical Flux ◽  
Surface Features ◽  
On Line ◽  
The Relationship

The critical flux was chosen to show surface features of the membrane fouling and it was determined by the flux-step method. The critical flux of on-line coagulation-UF, sedimentation-UF and sand filtration-UF was investigated and its value was 86.5 L/m2h80.5L/m2h and 68.1L/m2h, respectively. At the same time, the increasing rate of TMP were always lower than the corresponding values measured for the short-term flux-step experiments.

Optimising the operation of a MBR pilot plant by quantitative analysis of the membrane fouling mechanism

2005 ◽  
Vol 51 (6-7) ◽  
pp. 19-25 ◽  
Author(s):  
T. Jiang ◽  
M.D. Kennedy ◽  
B.F. Guinzbourg ◽  
P.A. Vanrolleghem ◽  
J.C. Schippers
Keyword(s):  
Membrane Fouling ◽  
Pilot Plant ◽  
Filter Cake ◽  
Municipal Wastewater ◽  
Hollow Fibre ◽  
Critical Flux ◽  
Membrane Pore ◽  
Operational Conditions ◽  
Temperature Conditions ◽  
Filtration Flux

In order to optimize some operational conditions of MBR systems, a MBR pilot plant equipped with a submerged hollow fibre membrane module was employed in this study. The pilot MBR was fed with real municipal wastewater and the filtration flux, backwashing interval, aeration frequency and temperature were varied. A filtration flux below 25 l/m2h is generally recommended, at below this flux, the MBR operated at sub-critical flux conditions, the filter cake was minimized and membrane fouling was mainly attributed to the membrane pore blocking. Moreover, the membrane fouling, at below 25 l/m2h, was more reversible to backwashing; above this value, backwashing became less efficient to clean the membrane. Less frequent backwashing (e.g. 600 s filtration/45 s backwashing) decreased the amount of fouling irreversible to backwashing and its performance was superior to that of frequent backwashing (e.g. 200 s filtration/15 s backwashing). The MBR suffered more fouling at low temperature conditions (e.g. at 13–14 °C) than at high temperature conditions (e.g. at 17–18 °C). A conceptual model was built up and successfully interpreted this temperature effect.

scholarly journals Critical flux investigation in treating o/w emulsion by TiO2/Al2O3-PVDF UF membrane

2017 ◽  
Vol 76 (10) ◽  
pp. 2785-2792 ◽  
Author(s):  
Xuesong Yi ◽  
Yong Wang ◽  
Limei Jin ◽  
Wenxin Shi
Keyword(s):  
Membrane Fouling ◽  
High Efficiency ◽  
Pure Water ◽  
Membrane System ◽  
Transmembrane Pressure ◽  
Step Method ◽  
Critical Flux ◽  
Zero Rate ◽  
Long Time

Abstract A standard transmembrane pressure (TMP) step method has been used in membrane fouling assessment in tube ultrafiltration (UF) membrane system treating oil water (o/w) emulsion operated at constant TMP. Three flux reduction curve with different o/w concentration based on TMP variation were concluded by experiment, then, to describe fouling behavior and identify the occurrence of fouling in the so-called critical flux. Furthermore, sub-critical and super-critical flux experiment with a long time was determined, and zero rate of flux reduction (dF/dt) was never found during the whole trial period, indicating that critical flux in o/w UF process with its strict definition could not be defined in this paper. However, quasi-critical flux exists, under which the pollution rate was very slow. Moreover, a high-efficiency four steps cleaning method: mechanic scraping, pure water wash, pure water reverse wash, and dosing cleaning, was explored. It concluded that critical flux in real o/w UF system determined by TMP-step method can be used to predict long-term critical behavior with useful data on fouling propensity.

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