scholarly journals Identification of fouling mechanisms in MBRs at constant flowrate: model applications and SEM-EDX characterizations

2017 ◽  
Vol 77 (1) ◽  
pp. 229-238 ◽  
Author(s):  
Bo Hu ◽  
Xingtao Zuo ◽  
Juan Xiong ◽  
Huimeng Yang ◽  
Menghua Cao ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactors ◽  
Transmembrane Pressure ◽  
X Ray ◽  
Inorganic Matter ◽  
Fundamental Understanding ◽  
Combined Models ◽  
Standard Models ◽  
Good Agreement

Abstract A fundamental understanding of fouling mechanisms is critical to improving filtration operations. The performance of four parallel membrane bioreactors (MBRs) with different sludge retention times (SRTs) was monitored during long-term constant flowrate filtration. The characteristics of the membrane and transmembrane pressure (TMP) profiles obtained were studied to demonstrate fouling mechanisms. Both classical blocking models and their combined models were evaluated. The intermediate model provided very good agreement with all the TMP data. However, the combined cake-intermediate and intermediate-standard models were more effective in the description of the experimental data. Contributions analysis indicated that the cake, intermediate and standard blocking models were the dominant fouling mechanisms. Scanning electron microscopy and energy dispersive X-ray (SEM-EDX) imaging showed that cake blocking by organic matter and standard blocking by inorganic matter made the main contributions to membrane fouling. The combined cake-intermediate and intermediate-standard models may be applicable to systems where these two models are consistent with the experimentally observed fouling mechanisms in an MBR.

Effect of low dosages of powdered activated carbon on membrane bioreactor performance

2012 ◽  
Vol 65 (5) ◽  
pp. 954-961 ◽  
Author(s):  
Maxime Remy ◽  
Hardy Temmink ◽  
Wim Rulkens
Keyword(s):  
Activated Carbon ◽  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Bioreactors ◽  
Powdered Activated Carbon ◽  
Filtration Time ◽  
Sludge Flocs ◽  
Operational Costs ◽  
Long Term Effect

Previous research has demonstrated that powdered activated carbon (PAC), when applied at very low dosages and long SRTs, reduces membrane fouling in membrane bioreactors (MBRs). This effect was related to the formation of stronger sludge flocs, which are less sensitive to shear. In this contribution the long-term effect of PAC addition was studied by running two parallel MBRs on sewage. To one of these, PAC was dosed and a lower fouling tendency of the sludge was verified, with a 70% longer sustainable filtration time. Low PAC dosages showed additional advantages with regard to oxygen transfer and dewaterability, which may provide savings on operational costs.

scholarly journals Dynamical Modelling and Simulation of Wastewater Filtration Process by Submerged Membrane Bioreactors

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Alain Zarragoitia ◽  
Sylvie Schetrite ◽  
Ulises J. Jauregui-Haza ◽  
Claire Albasi
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Model Development ◽  
Membrane Bioreactors ◽  
Transmembrane Pressure ◽  
Intermittent Aeration ◽  
Filtration Process ◽  
Solids Concentration ◽  
Wastewater Filtration ◽  
System Variables

A mathematical model was developed for the filtration process and the influence of aeration on Submerged Membrane Bioreactors. The dynamics of sludge attachment to and detachment from the membrane, in relation to the filtration and a strong intermittent aeration, were included in the model. The influence on the membrane fouling of intermittent aeration injected on the membrane surface, and its synchronization with intermittent filtration, were studied numerically and experimentally. For the evaluation of filtration cake development, the assumption of the presence of two cake layers (one dynamic and the other stable) was considered. The model development and simulation focused on the description of existing relationships among important system variables like mixed liquor suspended solids concentration, aeration, temperature of the sludge suspension, transmembrane pressure, and the fouling increase during the filtration process. The model obtained offers the possibility of improving the design configuration and operation strategies of Submerged Membrane Bioreactors in wastewater treatment, and it allows the of aeration-filtration cycles to be optimized.

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.

scholarly journals Fouling Mitigation by Cationic Polymer Addition into a Pilot-Scale Anaerobic Membrane Bioreactor Fed with Blackwater

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2383
Author(s):  
Magela Odriozola ◽  
Nicolás Morales ◽  
Jose R. Vázquez-Padín ◽  
Maria Lousada-Ferreira ◽  
Henri Spanjers ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Large Scale ◽  
Oxygen Demand ◽  
Cationic Polymer ◽  
Membrane Bioreactors ◽  
Cod Removal ◽  
Methanogenic Activity ◽  
Filtration Performance ◽  
Fouling Mitigation

Cationic polymers have proven to be suitable flux enhancers (FEs) in large-scale aerobic membrane bioreactors (MBRs), whereas in anaerobic membrane bioreactors (AnMBRs) research is scarce, and so far, only done at lab-scale. Results from MBRs cannot be directly translated to AnMBRs because the extent and nature of membrane fouling under anaerobic and aerobic conditions are different. Our research focused on the long-term effect of dosing the cationic polymer Adifloc KD451 to a pilot AnMBR, fed with source-separated domestic blackwater. A single dosage of Adifloc KD451 at 50 mg L−1 significantly enhanced the filtration performance in the AnMBR, revealed by a decrease in both fouling rate and total filtration resistance. Nevertheless, FE addition had an immediate negative effect on the specific methanogenic activity (SMA), but this was a reversible process that had no adverse effect on permeate quality or chemical oxygen demand (COD) removal in the AnMBR. Moreover, the FE had a long-term positive effect on AnMBR filtration performance and sludge filterability. These findings indicate that dosing Adifloc KD451 is a suitable strategy for fouling mitigation in AnMBRs because it led to a long-term improvement in filtration performance, while having no significant adverse effects on permeate quality or COD removal.

scholarly journals Combined Effect of Colloids and SMP on Membrane Fouling in MBRs

Membranes ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 118 ◽  
Author(s):  
Dimitra Banti ◽  
Manassis Mitrakas ◽  
Georgios Fytianos ◽  
Alexandra Tsali ◽  
Petros Samaras
Keyword(s):  
Membrane Fouling ◽  
Oxygen Demand ◽  
Membrane Bioreactors ◽  
Combined Effect ◽  
Transmembrane Pressure ◽  
Soluble Microbial Products ◽  
Treatment Efficiency ◽  
Membrane Pore ◽  
Microbial Products ◽  
Membrane Pore Size

Membrane fouling investigations in membrane bioreactors (MBRs) are a top research issue. The aim of this work is to study the combined effect of colloids and soluble microbial products (SMPs) on membrane fouling. Two lab-pilot MBRs were investigated for treating two types of wastewater (wwt), synthetic and domestic. Transmembrane pressure (TMP), SMP, particle size distribution and treatment efficiency were evaluated. Chemical Oxygen Demand (COD) removal and nitrification were successful for both kinds of sewage reaching up to 95–97% and 100%, respectively. Domestic wwt presented 5.5 times more SMP proteins and 11 times more SMP carbohydrates compared to the synthetic one. In contrast, synthetic wwt had around 20% more colloids in the mixed liquor with a size lower than membrane pore size (<400 nm) than domestic. Finally, the TMP at 36 days reached 16 kPa for synthetic wwt and 11 kPa for domestic. Therefore, synthetic wwt, despite its low concentration of SMPs, caused severe membrane fouling compared to domestic, a result that is attributed to the increased concentration of colloids. Consequently, the quantity of colloids and possibly their special characteristics play decisive and more important roles in membrane fouling compared to the SMP—a novel conclusion that can be used to mitigate membranes fouling.

scholarly journals Fouling modeling of the mixed liquor in MBR by the individual and combined models

2017 ◽  
Vol 76 (4) ◽  
pp. 761-775 ◽  
Author(s):  
Bo Hu ◽  
Xingtao Zuo ◽  
Juan Xiong ◽  
Ruiling Bao ◽  
Jiajie He
Keyword(s):  
Standard Model ◽  
Membrane Fouling ◽  
Membrane Filtration ◽  
Applied Pressure ◽  
Membrane Bioreactors ◽  
Dilution Ratio ◽  
Combined Model ◽  
Mixed Liquor ◽  
Combined Models ◽  
The Individual

To predict the membrane fouling phenomena in the membrane filtration operation, the individual models derived from Darcy's law and the corresponding combined models were employed to investigate the kind of models that provided better fits. The filtration of the mixed liquid from membrane bioreactors with different sludge retention time (SRT) at a constant pressure was carried out. The variation of applied pressure had significantly effect on the kind of the individual model provided better fit for the data at longer SRT and less effect for the data at shorter SRT, though it had less effect on the kind of the combined model that provided better fit. The kind of model that provided better fit did not change when the concentration of the diluted mixed liquor was at a certain range, even though the dilution ratio would lead to the variation of the prediction results. The cake-standard model and the complete-standard model provided good fits at different pressure and at different dilution ratio, respectively. The cake-standard and complete-standard models may be applicable to systems where these models are consistent with the experimentally observed fouling mechanisms.

THE LONG-TERM OPTICAL VARIABILITY PROPERTIES OF GAMMA-RAY BLAZAR 3C 273

2006 ◽  
Vol 15 (02) ◽  
pp. 261-272 ◽  
Author(s):  
BEN-ZHONG DAI ◽  
BIN-KAI ZHANG ◽  
YANG XIANG ◽  
JIAN-PING YANG ◽  
LIN LIN ◽  
...  
Keyword(s):  
Correlation Function ◽  
Gamma Ray ◽  
The Other ◽  
Optical Variability ◽  
X Ray ◽  
Self Consistent ◽  
Data Points ◽  
Quasar 3C 273 ◽  
Good Agreement

We compile all the available optical B band data for the quasar 3C 273 from 1887 to 2001 from the literature, and obtain 1,890 data points. Using these data, we analyze the light curve properties by means of the Jurkevich method and the discrete correlation function (DCF) method. The analysis results of the two methods are self consistent; the cross-checked variability period is 13.51 years. The 13.51-year period variation in the optical band is in good agreement with the previous results in the optical and X-ray bands. However, the other claimed periods of the quasar 3C 273 are not confirmed in our work.

Ultrafiltration of defatted whey: improving performance by limiting membrane fouling

1993 ◽  
Vol 60 (1) ◽  
pp. 79-88 ◽  
Author(s):  
Georges Daufin ◽  
Françoise Michel ◽  
Jean-Pierre Labbé ◽  
Auguste Quemebais ◽  
André Grangeon
Keyword(s):  
Calcium Phosphate ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Inorganic Membrane ◽  
Transmembrane Pressure ◽  
Protein Fouling ◽  
Constant Ph ◽  
Concentration Polarization Layer ◽  
Protein Rejection ◽  
Good Agreement

SummaryDefatted whey was obtained by aggregating residual fat to calcium phosphate precipitates and separating the precipitate by membrane microfiltration (pore diameter 0·2 μm). When ultrafiltering this defatted whey the performance of an inorganic membrane (molecular mass cut-off, 10 kDa) was limited by the large concentration of Ca and phosphates. Consequently, the influence of the aggregation pH (either decreasing or constant) on membrane fouling has been studied for ultrafiltration (UF) of defatted sweet whey and defatted whey UF retentates (protein content up to 30g l–1). In all experiments protein rejection was 100%. When pH was kept constant during the pretreatment, membrane fouling was significantly lowered. Hydraulic resistances ascribed to irreversible fouling were in good agreement with fouled membrane analyses performed by i.r. and X-ray photoelectron spectroscopies. They showed that provided a low Ca and phosphate content was maintained in the microfiltrate, which was achieved at constant pH, no apatite was detected within the membrane, and proteins were less fouling. On the other hand, the amount of fouling material depended on the transmembrane pressure gradient along the hydraulic path. On the membrane surface, the higher the pressure, the higher the fouling. In the membrane bulk, the fouling heterogeneity depended on the ability of the defatted whey to precipitate apatite. If it did, the higher the pressure, the higher the calcium phosphate and the protein fouling. With other phosphate structures, the bulk fouling depended on the barrier formed by surface fouling layers and the protein concentration polarization layer, which were more resistant to solute and solvent transfer under higher pressure, where they were thicker.

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