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Updated: Jun 5, 2026
Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge
Published on: September 26, 2016
Correlation between fouling propensity of soluble extracellular polymeric substances and sludge metabolic activity
1Department of Environmental Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 402, Taiwan, ROC. siangchen.wu@gmail.com
Abstract:
Soluble extracellular polymeric substances (EPSs) cause membrane fouling in membrane bioreactors (MBRs), correlated with MBR sludge characteristics. Effects of F/M ratios on the evolution of soluble EPSs, fouling propensity of supernatants, and sludge metabolic activity were measured in this study in a two-period sequencing batch reactor (SBR). The experimental results show that fouling propensity was directly correlated with soluble-EPS concentration and composition. Sludge that had entirely lost active cells by long-term starvation released 64.4 ± 0.9 mg/L of humic acids, which caused a rapid increase in membrane resistance (40.67 ± 2.24 × 10(11) m(-1)) during fouling tests. During short-term starvation, induced by incubation at a normal to low F/M ratio of 0.05 d(-1), sludge can use previously secreted utilization-associated products (UAPs) to maintain endogenous respiration. Therefore, the strategies of accumulating sludge and prolonging sludge retention time in MBRs may create long-term starvation and promote membrane fouling.
Insights
Soluble extracellular polymeric substances (EPSs) in membrane bioreactors (MBRs) contribute to membrane fouling. Long-term sludge starvation, often caused by high sludge retention times, significantly increases fouling potential.
Area of Science:
- Environmental Science
- Biotechnology
Background:
- Membrane bioreactors (MBRs) are widely used for wastewater treatment.
- Soluble extracellular polymeric substances (EPSs) are a major cause of membrane fouling in MBRs.
- The characteristics of MBR sludge influence EPS production and fouling potential.
Purpose of the Study:
- To investigate the effects of food-to-microorganism (F/M) ratios on soluble EPS evolution.
- To assess the fouling propensity of supernatants under different F/M ratios.
- To understand the relationship between sludge metabolic activity and membrane fouling.
Main Methods:
- Utilized a two-period sequencing batch reactor (SBR) to simulate MBR conditions.
- Measured soluble EPS concentration and composition.
- Assessed supernatant fouling propensity and sludge metabolic activity at varying F/M ratios.
Main Results:
- Fouling propensity directly correlated with soluble EPS concentration and composition.
- Long-term sludge starvation (no active cells) released humic acids, rapidly increasing membrane resistance.
- Short-term starvation allowed sludge to maintain respiration using utilization-associated products (UAPs).
Conclusions:
- Accumulating sludge and prolonging sludge retention time in MBRs can lead to long-term starvation.
- Long-term starvation promotes the release of fouling-inducing substances, exacerbating membrane fouling.
- Optimizing F/M ratios and sludge retention times is crucial for mitigating membrane fouling in MBRs.
