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Updated: Jul 2, 2026
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Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge
Published on: September 26, 2016
How does shear affect aggregation in granular sludge sequencing batch reactors? Relations between shear,
E Dulekgurgen1, N Artan, D Orhon
1Environmental Engineering Department, Pamukkale University, Denizli, Turkey. edulekgurgen@pau.edu.tr
Summary
Understanding aggregative physiology requires managing physical stress. This study shows that reducing shear stress enhances biomass formation and granulation, crucial for wastewater treatment systems.
Area of Science:
- Environmental Microbiology
- Biotechnology
- Wastewater Engineering
Background:
- Aggregative physiology is key for microbial community development in wastewater treatment.
- Physical stress, including shear forces, significantly impacts microbial aggregate formation and stability.
- Optimizing conditions for microbial growth is essential for efficient biological wastewater treatment.
Purpose of the Study:
- To investigate the relationship between physical stress and biomass characteristics in an anaerobic-aerobic sequencing batch reactor.
- To determine how hydraulic selection pressures influence microbial granulation and survival.
- To understand the role of cell surface hydrophobicity and extracellular polymeric substances (EPS) in aggregative physiology under varying stress.
Main Methods:
- Operated a lab-scale sequencing batch reactor under anaerobic-aerobic conditions.
- Manipulated settling time and hydrodynamic shear rates from mechanical mixing and aeration.
- Monitored biomass characteristics, including granule formation, settling properties, cell surface hydrophobicity, and EPS composition.
Main Results:
- Extreme mechanical shear initially hindered settling properties and caused biomass washout, despite initial granule formation.
- Relaxing shear stress promoted biomass formation, improved settling, and advanced granulation.
- Cell surface hydrophobicity and EPS production increased with granulation but decreased upon process disturbance.
- A direct correlation was observed between hydrophobicity and EPS composition (ExoPN/ExoPS).
Conclusions:
- Managing physical stress, particularly shear forces, is critical for successful granulation and survival in aggregative physiology.
- Optimized shear stress conditions enhance biomass formation, settling, and the production of key EPS components.
- Understanding these relationships is vital for designing and operating efficient biological wastewater treatment processes.
