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Impact of sludge cation distribution pattern on its filterability in membrane bioreactor
Haifeng Zhang1, Zhongping Wang2, Lanhe Zhang2
1School of Chemistry Engineering, Northeast Dianli University, Jilin 132012, Jilin, PR China; Department of Civil and Environmental Engineering, Texas Tech University, 10th and Akron, Lubbock, TX 79409-1023, USA.
Bioresource Technology
|September 3, 2014
Summary
Cation concentrations in activated sludge extracellular polymeric substances (EPSs) influence structure and filterability. Divalent cations like Ca(2+) and Fe(3+) significantly improve flocculability, while Na(+) has a minor effect, impacting sludge performance.
Area of Science:
- Environmental Science
- Biotechnology
- Chemical Engineering
Background:
- Activated sludge process performance is heavily influenced by the composition and structure of extracellular polymeric substances (EPSs).
- Cation distribution within EPSs, particularly in the outer layers, plays a crucial role in the stratification of polysaccharides (PS) and proteins (PN).
Purpose of the Study:
- To investigate the impact of different cation valences (Na+, Ca2+, Fe3+) on the stratification structure of PS and PN within activated sludge EPSs.
- To determine the correlation between cation distribution, EPS composition, and activated sludge filterability, assessed using the modified fouling index (MFI).
Main Methods:
- Analysis of cation distributions (Na+, Ca2+, Fe(3+)) in various EPS fractions (supernatant, slime, loosely bound EPS (LB), tightly bound EPS (TB), and pellet).
- Quantification of polysaccharides (PS) and proteins (PN) in different EPS fractions.
- Measurement of activated sludge filterability using the modified fouling index (MFI).
- Statistical analysis to correlate MFI with PN and PS concentrations in different fractions.
Main Results:
- Monovalent Na+ slightly reduced flocculability (9.75%), while divalent Ca2+ and Fe3+ significantly increased it.
- The MFI showed a strong correlation with PN in the supernatant (rp=0.8593), slime (rp=0.7218), and LB EPS (rp=0.8012).
- MFI had moderate to weak correlations with PS in the supernatant, slime, and LB EPS, and negligible correlations with PN or PS in TB EPS or pellet.
- Lower PN or PS content in the supernatant positively impacted activated sludge filterability.
Conclusions:
- Cation valence significantly affects activated sludge flocculability and EPS structure.
- Proteins in the supernatant and loosely bound EPS are key indicators for predicting activated sludge filterability.
- Optimizing cation composition and reducing supernatant PN/PS can enhance activated sludge process efficiency and filterability.
Keywords:
BioflocculationExtracellular polymeric substancesFilterabilityMembrane bioreactorModified fouling indexMore Related Videos
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