Simulation of membrane fouling considering mixed liquor viscosity and variation of shear stress on membrane surface

2011 ◽  
Vol 63 (2) ◽  
pp. 270-275 ◽  
Author(s):  
Hlwan Moe Zaw ◽  
Tari Li ◽  
H. Nagaoka
Keyword(s):  
Shear Stress ◽  
Standard Deviation ◽  
Membrane Fouling ◽  
Shear Force ◽  
Extracellular Polymeric Substances ◽  
Membrane Surface ◽  
Force Sensor ◽  
Bulk Liquid ◽  
Mixed Liquor ◽  
Flat Sheet

Simulation of membrane fouling in MBR was conducted considering accumulation, detachment and consolidation of extracellular polymeric substances accumulated on membrane surface. The fluctuation of shear stress working on membrane surface and the influence of the viscosity of mixed liquor were considered for the evaluation of shear stress. A flat-sheet-type membrane module was used and the change of trans-membrane pressure was measured in a laboratory-scale MBR reactor. Shear stress working on membrane surface caused by aeration was measured by a shear force sensor changing viscosity of bulk liquid. Effective shear stress on membrane surface was defined in the model as the sum of time-averaged shear stress and three times of standard deviation. The increase in the trans-membrane pressure was accurately simulated by the developed model suggesting validity of the developed fouling model and the idea of the effective shear stress on membrane surface.

scholarly journals Biomass Characteristics and Their Effect on Membrane Bioreactor Fouling

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2867 ◽  
Author(s):  
Petros K. Gkotsis ◽  
Anastasios I. Zouboulis
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Suspended Solids ◽  
Extracellular Polymeric Substances ◽  
Membrane Surface ◽  
Membrane Resistance ◽  
Soluble Microbial Products ◽  
Gelling Properties ◽  
Microbial Products ◽  
Soluble Part

Biomass characteristics are regarded as particularly influential for fouling in Membrane Bio-Reactors (MBRs). They primarily include the Mixed Liquor Suspended Solids (MLSS), the colloids and the Extracellular Polymeric Substances (EPS). Among them, the soluble part of EPS, which is also known as Soluble Microbial Products (SMP), is the most significant foulant, i.e., it is principally responsible for membrane fouling and affects all fundamental fouling indices, such as the Trans-Membrane Pressure (TMP) and the membrane resistance and permeability. Recent research in the field of MBRs, tends to consider the carbohydrate fraction of SMP (SMPc) the most important characteristic for fouling, mainly due to the hydrophilic and gelling properties, which are exhibited by polysaccharides and allow them to be easily attached on the membrane surface. Other wastewater and biomass characteristics, which affect indirectly membrane fouling, include temperature, viscosity, dissolved oxygen (DO), foaming, hydrophobicity and surface charge. The main methods employed for the characterization and assessment of biomass quality, in terms of filterability and fouling potential, can be divided into direct (such as FDT, SFI, TTF100, MFI, DFCM) or indirect (such as CST, TOC, PSA, RH) methods, and they are shortly presented in this review.

Effects of mixed liquor pH on membrane fouling and micro-pollutant removals in membrane bioreactors for municipal landfill leachate treatment

2015 ◽  
Vol 72 (5) ◽  
pp. 770-778 ◽  
Author(s):  
Samunya Sanguanpak ◽  
Chart Chiemchaisri ◽  
Wilai Chiemchaisri ◽  
Kazuo Yamamoto
Keyword(s):  
Landfill Leachate ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Membrane Bioreactors ◽  
Leachate Treatment ◽  
Mixed Liquor ◽  
Municipal Landfill ◽  
Inorganic Substances ◽  
Ph Level ◽  
Ph Variations

This research investigated the membrane fouling and micro-pollutant removals in treatment of municipal landfill leachate at various pH levels (i.e. 5.5, 6.5, 7.5, and 8.5) using membrane bioreactors. The findings revealed that membrane fouling was influenced by the pH level of mixed liquor, with pH 5.5 exhibiting the most severe membrane fouling. At pH 5.5, proteins and carbohydrates were predominant in the membrane foulants, while at pH 8.5 humic-like and inorganic substances constituted the largest proportion of the foulants on the membrane surface. The removal efficiencies of micro-pollutants (bisphenol-A; 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-4-methylbutylphenol) were nevertheless insignificantly influenced by the pH levels of mixed liquor. In addition, the removal rates of the compounds at pH 5.5 were slightly lower vis-à-vis at the higher pH levels. The micro-pollutant retention on the fouled membranes was also significant and highest under the mixed liquor pH of 8.5. Furthermore, the experiments demonstrated that the varying degrees of rejection by the fouled membranes could be attributed to the alteration of foulant characteristics as a result of the pH variations.

scholarly journals A Study on Membrane Filtration Characteristics of Methanogenic Mixed Liquor in Two Phase Anaerobic Digestion of Food Waste

2020 ◽  
Vol 42 (3) ◽  
pp. 151-163
Author(s):  
Min-Ju Park ◽  
Gyu-Tae Seo
Keyword(s):  
Anaerobic Digestion ◽  
Food Waste ◽  
Membrane Fouling ◽  
Membrane Filtration ◽  
Membrane Surface ◽  
Solid Retention Time ◽  
Two Phase ◽  
Mixed Liquor ◽  
Cross Flow Filtration ◽  
Cake Layer

Objectives:An experimental study was conducted to investigate the membrane filtration characteristics of mixed liquor in methanogenic reactor to extend solid retention time (SRT) in food waste anaerobic digestion system.Methods:On the basis of the particle size distribution (0.5~700 µm) of the methanogenic mixed liquor, three grade membranes (MF, UF, NF) were tested in a stirred cell filtration and a plate type module. Furthermore foulants of membrane, especially UF, was investigated by SEM-EDS, FTIR, SEC.Results and Discussion:As a result UF membrane was selected for stable filtration of the liquor in terms of flux (2.51 L/m<sup>2</sup>･h･bar) and the flux recovery (100%) as well as filtration resistance (Total 7.15.E+13 m<sup>-1</sup>). Average flux was 18 L/m<sup>2</sup>･h･bar for the selected UF membrane in cross flow filtration using a flat plate module. The filtration results showed that membrane fouling was caused by gel and cake layer formed on the membrane surface and 90% of the initial flux could be recovered by physical washing. It was identified that major fouling causing materials were byproducts of carbohydrate and protein decomposition, and small amount of inorganic substance detected on the membrane surface were salt and struvite like materials.Conclusions:Based on the membrane filtration characteristics analyzed from the study, the UF membrane coupled anaerobic digestion is feasible to be applied as a novel food waste treatment system for SRT extension of the methanogenic reactor.

Hydrodynamic Modeling of the Helical Membrane Modules

2013 ◽  
Author(s):  
Fengxia Liu ◽  
Wei Wei ◽  
Guan Wang ◽  
Xiaofei Xu ◽  
Zhijun Liu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Kinetic Energy ◽  
Numerical Simulations ◽  
Turbulent Kinetic Energy ◽  
Membrane Fouling ◽  
Concentration Polarization ◽  
Membrane Surface ◽  
Helical Angle ◽  
Flat Membrane ◽  
Membrane Modules

Membrane fouling and concentration polarization can be greatly mitigated by using the helical membrane modules to enhance the mass transport process. In this study, experiments and computational fluid dynamics were used to investigate the transport phenomena in a helical membrane filter with several helical membrane modules. A model is constructed with a square filter which has three helical membrane modules embedded as not only turbulence promoters but also filtering elements. Direct numerical simulations based on the Navier-Stokes equations are performed over a range of characteristic parameters of membrane and aeration flux. The distributions of local parameters such as velocity, shear stress and turbulent kinetic energy on the membrane surface were obtained by numerical simulations with different helical angle and aeration flux. These parameters are directly related to mass transport enhancement. Results show that both wall shear stress and turbulent kinetic energy obtained from helical membrane modules are larger than those from flat membrane modules, and they increase with an increase of the helical angle. The average shear stress on the membrane surface increases from 0.097 Pa to 0.217 Pa as the helical angle changes from 0° to 360°. In addition, the flow field was analyzed by means of noncontact measuring and visualization device-Particle Image Velocimetry (PIV), and the vorticity as well as the turbulent kinetic energy were obtained from the velocity distribution. The measured data are in agreement with the numerical results. From the research, we can see that the helical membrane modules can enhance the transfer efficiently compared to the flat membrane modules, which means the concentration polarization and membrane fouling can be alleviated efficaciously, it can be concluded that the helical membrane modules can play an important role in government actions membrane separation engineering and its application prospect in industry is very broad.

scholarly journals Numerical and experimental investigation for cleaning process of submerged outside-in hollow fiber membrane

2017 ◽  
Vol 76 (6) ◽  
pp. 1283-1299 ◽  
Author(s):  
Xingfei Guo ◽  
Yaowu Wang ◽  
Hongwei Zhang ◽  
Pengfei Li ◽  
Cong Ma
Keyword(s):  
Shear Stress ◽  
Hollow Fiber ◽  
Membrane Fouling ◽  
Cfd Simulation ◽  
Hollow Fiber Membrane ◽  
Membrane Surface ◽  
Experimental Studies ◽  
Membrane System ◽  
Fiber Membrane ◽  
The Impact

Membrane fouling has limited extensive applications for hollow fiber membranes in water treatment. Backwashing and air scouring can effectively solve this problem in the submerged outside-in hollow fiber membrane system. In this study, variation of the fouling layer on the membrane surface during backwashing and the impact of shear stress caused by air scouring on fouling removal were investigated through computational fluid dynamics (CFD) simulation. The backwashing and air scouring process were simulated using CFD and the results were verified by experimental studies. The results of experimental studies are in accordance with the simulation results. During the backwashing process, the velocity profile inside the reactor was presented, and visualization of the particle movement to illustrate the dynamic peeling process of the fouling layer on the membrane surface was also shown. The formation of uneven cleaning reveals that the upper region of the fibers has an excellent cleaning effect during backwashing. After that, the supporting role of air scouring was investigated in the study. It is concluded that the lower part and the middle region of the fibers suffer greater shear stress by analyzing the velocity contours and vectors, and the analysis results indicated that air scouring can further remove membrane fouling.

scholarly journals Effect of Mixed Liquor Volatile Suspended Solids on Membrane Fouling During Short and long-term Operation of Membrane Bioreactor

2015 ◽  
Vol 11 (21) ◽  
pp. 137-155 ◽  
Author(s):  
Edson Baltazar Estrada-Arriaga ◽  
Petia Mijaylova Nacheva ◽  
Liliana García-Sánchez
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Suspended Solids ◽  
Membrane Surface ◽  
Waste Water Treatment ◽  
Critical Flux ◽  
Term Operation ◽  
Mixed Liquor ◽  
Submerged Membrane Bioreactor ◽  
The Impact

The aim of this study was to examine the impact of different Mixed Liquor Volatile Suspended Solids (MLVSS) concentrations on membrane fouling,in a submerged Membrane Bioreactor (MBR) at short and longterm MBRoperation for waste water treatment. Three laboratory-scale in a submerged MBR system were operated under critical flux, subcritical flux,and an intermittent suction time and backwashing conditions. At short-term MBR operation with mixed liquors of 4,200 and 6,150 mg MLVSSL−1, the hydraulic resistance of membranes followed a same trajectory with averages of 5.0E+12m−1, whereas for 7,940 mg MLVSSL−1, a highresistance of up to 1.7E+13m−1was obtained. The result showed thathigh biomass concentrations decreased to permeability due to a bio-layer formed in the membrane surface and high Extracellular Polymeric Substance (EPS).

scholarly journals Evaluation of the importance of various operating and sludge property parameters to the fouling of membrane bioreactors

2011 ◽  
Vol 64 (6) ◽  
pp. 1340-1346 ◽  
Author(s):  
F. Y. Sun ◽  
X. Y. Li
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Extracellular Polymeric Substances ◽  
Membrane Surface ◽  
Cross Flow ◽  
Correlation Coefficients ◽  
Single Fibre ◽  
Cake Layer ◽  
The Cross ◽  
Filtration Flux

A single-fibre microfiltration system was employed to investigate the importance of various operating and sludge property parameters to the membrane fouling during sludge filtration. The sludge was obtained from a submerged membrane bioreactor (SMBR). A series of comparative and correlative filtration and fouling tests were conducted on the influence of the operating variables, sludge properties and the liquid-phase organic substances on the membrane fouling development. The test results were analysed statistically with Pearson's correlation coefficients and the stepwise multi-variable linear regression. According to the statistical evaluation, the membrane fouling rate has a positive correlation with the biopolymer cluster (BPC) concentration, sludge concentration (mixed liquor suspended solids, MLSS), filtration flux and viscosity, a negative correlation with the cross-flow velocity, and a weak correlation with the extracellular polymeric substances and soluble microbial products. BPC appear to be the most important factor to membrane fouling development during the sludge filtration, followed by the filtration flux and MLSS concentration. The cross-flow rate also is important to the fouling control. It is argued that, during membrane filtration of SMBR sludge, BPC interact with sludge flocs at the membrane surface to facilitate the deposition of the sludge cake layer, leading to serious membrane fouling.

scholarly journals Effects of electrochemical processes application on the modification of mixed liquor characteristics of an electro-membrane bioreactor (e-MBR)

2018 ◽  
Vol 78 (11) ◽  
pp. 2364-2373 ◽  
Author(s):  
André Aguiar Battistelli ◽  
Rayra Emanuelly da Costa ◽  
Leonardo Dalri-Cecato ◽  
Tiago José Belli ◽  
Flávio Rubens Lapolli
Keyword(s):  
Electric Field ◽  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Extracellular Polymeric Substances ◽  
Municipal Wastewater ◽  
Municipal Wastewater Treatment ◽  
Floc Size ◽  
Mixed Liquor ◽  
Average Value ◽  
Electrochemical Processes

Abstract This study evaluated the effects of electrochemical processes on the mixed liquor characteristics of an electro-membrane bioreactor (e-MBR) applied to municipal wastewater treatment. A laboratory-scale e-MBR was assessed under two experimental runs: without the electric field (run I) and with electric field, controlled by the application of an electric current set in 10.0 A m−2 under intermittent exposure mode of 6 minutes ON/18 minutes OFF (run II). The electric field caused approximately 55% removal of both soluble microbial products (SMP) and extracellular polymeric substances (EPS), whereas the proteins/carbohydrates ratio in EPS was increased from 1.9 in the run I to 2.9 in run II, leading to an increment of flocs' hydrophobicity. Additionally, the sludge floc size average value was reduced from 42.2 μm in run I to 24.6 μm in run II, which led to a significant enhancement in the sludge settleability. As a result, the membrane fouling rate was always less than 3.80 mbar d−1 in run II, whereas in run I these values reached up to 34.7 mbar d−1. These results demonstrated that the electrochemical processes enhanced the mixed liquor filterability. Therefore, their implementation represents a great alternative to improve the operational stability of membrane bioreactors.

Performances and fouling control of a flat sheet membrane in a MBR pilot-plant

2010 ◽  
Vol 61 (9) ◽  
pp. 2185-2192 ◽  
Author(s):  
A. Grélot ◽  
P. Grelier ◽  
A. Tazi-Pain ◽  
B. Lesjean ◽  
U. Brüss ◽  
...  
Keyword(s):  
Pilot Plant ◽  
Membrane Surface ◽  
Membrane Technology ◽  
Operating Conditions ◽  
Mixed Liquor ◽  
Fouling Control ◽  
Biological Stress ◽  
Flat Sheet ◽  
Flat Sheet Membrane ◽  
Sheet Membrane

This paper deals with the performance and the optimisation of the hydraulic operating conditions of the A3 Water Solutions flat sheet membrane technology in a MBR pilot-plant to achieve a satisfying fouling control and also a reduction in the required aeration. Two vertically stacked modules were tested at pilot-scale at Anjou Recherche under typical biological operating conditions (mixed liquor suspended solids concentration (MLSS) = 10 g/l; sludge retention time (SRT) = 28 days; food to microorganism ratio (F/M)= 0.12 kg COD/kg MLSS/d). The use of a double-deck and of specific backwashes for this membrane technology enabled to achieve satisfying membrane performances for a net flux of 25 L h−1 m−2, 20°C at a low specific aeration demand per membrane surface (SADm = 0.2 Nm3 h−1 m−2) which corresponds to a specific aeration demand per permeate volume unit (SADp) of 8 Nm3 air/m3 permeate, which is lower than reported for many commercial membrane systems. The mixed liquor characteristics (foaming, MLSS concentration) appeared to influence the fouling behaviour of the membranes but no correlation was found with the fouling rate. However, with the new operating conditions, the system is robust and can cope with fouling resulting from biological stress and daily peak flows for MLSS concentrations in the membrane tank up to 18 g/l.

scholarly journals Characterization of the Fouling Layer on the Membrane Surface in a Membrane Bioreactor: Evolution of the Foulants’ Composition and Aggregation Ability

Membranes ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 85 ◽  
Author(s):  
Linlin Yan ◽  
Ruixue Li ◽  
Yu Song ◽  
Yanping Jia ◽  
Zheng Li ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Extracellular Polymeric Substances ◽  
Membrane Surface ◽  
Extracellular Dna ◽  
Transmembrane Pressure ◽  
Average Roughness ◽  
Three Stages ◽  
Fast Rise

In this study, the characteristics of membrane foulants were analyzed with regard to morphology, composition, and aggregation ability during the three stages of transmembrane pressure (TMP) development (fast–slow–fast rise in TMP) in a steady operational membrane bioreactor (MBR). The results obtained show that the fouling layer at the slow TMP-increase stage possessed a higher average roughness (71.27 nm) and increased fractal dimension (2.33), which resulted in a low membrane fouling rate (0.87 kPa/d). A higher extracellular DNA (eDNA) proportion (26.12%) in the extracellular polymeric substances (EPS) resulted in both higher zeta potential (-23.3 mV) and higher hydrophobicity (82.3%) for initial foulants, which induced and increased the protein proportion in the subsequent fouling layer (74.11%). Furthermore, the main composition of the EPS shifted from protein toward polysaccharide dominance in the final fouling layer. The aggregation test confirmed that eDNA was essential for foulant aggregation in the initial fouling layer, whereas ion interaction significantly affected foulant aggregation in the final fouling layer.

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