Activating Biocake Communities Retards Jumps of Transmembrane Pressure in Membrane Bioreactors

Area of Science:

• Environmental Science
• Microbiology
• Chemical Engineering

Background:

• Sudden transmembrane pressure (TMP) jumps in membrane bioreactors (MBRs) exacerbate membrane fouling, limiting their practical application.
• The mechanisms linking bacterial activity in biocakes to TMP jumps are not fully understood.

Purpose of the Study:

• To investigate the role of bacterial activity in biocakes in causing TMP jumps.
• To evaluate the effectiveness of nutrient-rich backwash solutions in mitigating TMP jumps and membrane fouling.

Main Methods:

• Membrane bioreactor (MBR) fouled membranes were subjected to various backwash protocols with different nutrient loadings (nitrate and sodium acetate).
• Filtration tests were conducted to measure TMP jump rates.
• Biocake characterization was performed to assess bacterial viability, activity, and biomolecule accumulation.
• Ecological null model analyses were used to understand biocake community structure.

Main Results:

• Backwashing with a nutrient solution (NaNO3 and NaAc) significantly reduced the TMP jump rate (1.40 kPa/d) compared to tap water (3.56 kPa/d).
• Nutrient-rich backwash increased bacterial viability and activity in biocakes while decreasing biomolecule accumulation.
• Key bacterial taxa (e.g., *Aeromonas*, *Chitinophagaceae*) involved in nitrate reduction and biomolecule degradation were identified.
• Deterministic processes primarily shaped biocake communities under high nutrient conditions.

Conclusions:

• Bacterial activity within biocakes plays a critical role in the development of TMP jumps in MBRs.
• Supplying adequate nutrients to biocake bacteria is an effective strategy to mitigate TMP jumps and control membrane fouling.
• This study offers potential alternative approaches for managing membrane fouling in MBR systems.