Incorporating Biocarriers in Membrane Bioreactors for Wastewater Treatment and Membrane Fouling Control From a Microbial Perspective

Membrane bioreactors (MBRs) are widely applied for advanced wastewater treatment, but membrane fouling remains a major constraint on long-term operational stability and economic viability. Biocarrier-assisted MBRs (BC-MBRs) have emerged as a promising strategy to simultaneously improve pollutant removal and mitigate fouling through microbial ecological regulation. This review critically evaluates polymeric, carbon-based, and iron-based biocarriers, with emphasis on their effects on microbial community assembly, biofilm development, extracellular polymeric substances (EPS), soluble microbial products (SMP), and membrane fouling. Current evidence indicates that biocarriers enhance biomass retention, promote microbial functional specialization, and create stratified ecological niches that support nitrifiers, denitrifiers, and degraders of recalcitrant contaminants. Membrane fouling is increasingly recognized as a reactor-wide ecological process involving interactions among bulk sludge, membrane cake layers, and carrier-associated biofilms. Quorum sensing (QS) and quorum quenching (QQ) are further considered as biologically targeted approaches for controlling biofilm development and fouling. Reported QQ applications have achieved approximately 10%-80% reductions in EPS production and 25%-65% reductions in biofilm accumulation, while extending membrane filtration cycles by two- to four-fold. Integrating QQ with biocarrier-based systems represents a promising direction for next-generation fouling control. Future research should prioritize mechanistic carrier-microbe-fouling relationships, multifunctional carrier design, intelligent process control, and pilot- and full-scale validation. Overall, BC-MBRs provide a versatile platform for enhancing treatment efficiency, fouling resistance, and operational sustainability in advanced wastewater treatment.