Typical Heterotrophic and Autotrophic Nitrogen Removal Process Coupled with Membrane Bioreactor: Comparison of...

Area of Science:

• Environmental Science
• Microbiology
• Chemical Engineering

Background:

• Membrane bioreactors (MBRs) are crucial for wastewater treatment, but membrane fouling remains a challenge.
• Limited research exists on microbial metabolites' role in membrane fouling during nitrogen removal in MBRs.

Purpose of the Study:

• To compare membrane fouling behavior between anoxic-oxic (AO) and partial nitritation-anammox (PNA) MBR processes.
• To investigate the influence of microbial metabolites on membrane fouling in these MBR systems.

Main Methods:

• Comparative analysis of AO-MBR and PNA-MBR under identical nitrogen loading rates and MLSS concentrations.
• Monitoring transmembrane pressure (TMP) to assess fouling.
• Analysis of supernatant and extracellular polymeric substances (EPS) for chemical composition and structural properties.

Main Results:

• PNA-MBR exhibited significantly more severe membrane fouling than AO-MBR, indicated by higher TMP.
• PNA-MBR supernatant contained higher concentrations of protein, polysaccharides, and low-molecular-weight humic substances.
• EPS from PNA-MBR sludge showed looser protein structures, increased hydrophobicity, and higher humic substance content, contributing to fouling.

Conclusions:

• Microbial metabolites, particularly hydrophobic organics and humic substances produced by bacteria like *Candidatus* Brocadia and *Chloroflexi*, exacerbate membrane fouling in PNA-MBRs.
• Hydrophilic membrane modification is recommended to mitigate severe fouling in PNA-MBR systems.