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Relation between EPS adherence, viscoelastic properties, and MBR operation: Biofouling study with QCM-D
Amer Sweity1, Wang Ying, Mohammed S Ali-Shtayeh
1Ben Gurion University of the Negev, Zuckerberg Institute for Water Research, Sede Boqer Campus, Midreshet Ben Gurion, 84990, Israel.
Water Research
|October 22, 2011
Summary
Optimizing solids retention time (SRT) in membrane bioreactors (MBRs) minimizes membrane fouling by altering extracellular polymeric substances (EPS). Lowering sludge removal rates improves EPS properties, reducing fouling and enhancing MBR performance.
Area of Science:
- Environmental Engineering
- Biotechnology
- Materials Science
Background:
- Membrane bioreactor (MBR) technology is hindered by membrane fouling, primarily caused by extracellular polymeric substances (EPS) in biomass.
- Solids retention time (SRT) is a critical operational parameter influencing EPS composition and membrane fouling in MBR systems.
Purpose of the Study:
- To investigate the direct impact of sludge removal rates on EPS adherence, viscoelastic properties, and their correlation with membrane fouling.
- To elucidate the relationship between SRT, EPS composition, and the fouling propensity in MBRs.
Main Methods:
- Extracted EPS from a UF membrane in a hybrid growth MBR operated at varying sludge removal rates (5.9 to 59 L/day, corresponding to SRTs of 3 to 30 days).
- Utilized quartz crystal microbalance with dissipation monitoring (QCM-D) to analyze EPS adherence and adsorption kinetics onto a PVDF-coated sensor.
- Employed Voigt-based modeling to calculate thickness, shear modulus, and shear viscosity of adsorbed EPS layers.
- Corroborated findings with confocal laser scanning microscopy (CLSM) to visualize EPS distribution near the membrane surface.
Main Results:
- Changes in sludge removal rate significantly altered EPS adherence and viscoelastic properties, directly correlating with membrane fouling rates.
- Lower sludge removal rates (longer SRTs) resulted in reduced EPS adherence and altered viscoelasticity, indicating decreased fouling potential.
- QCM-D data suggested that elevated fouling at higher sludge removal rates is linked to increased EPS adherence and a more fluid EPS layer.
- CLSM confirmed thicker EPS layers near the membrane surface under conditions inducing higher fouling.
Conclusions:
- SRT is a key factor controlling EPS properties and membrane fouling in MBRs.
- Optimizing SRT by adjusting sludge removal rates can mitigate membrane fouling through modulation of EPS characteristics.
- Understanding EPS viscoelasticity and adherence is crucial for designing and operating efficient MBR systems.
