Fabrication and characterization of PVC/ag-based TPU membranes for MBRs: Antifouling performance and mechanistic fouling analysis via Hermia and Bolton models

Understanding membrane fouling mechanisms is essential for the reliable design and stable operation of membrane bioreactor (MBR) systems. In this study, the fouling behavior of PVC/TPU composite membranes incorporating silver ions was systematically investigated using classical and compound fouling models. Antibacterial membranes were fabricated via the non-solvent-induced phase separation (NIPS) method and evaluated in a laboratory-scale MBR through three consecutive filtration–cleaning cycles. Flux decline data were analyzed using the resistance-in-series (RIS) model, Hermia single-mechanism fouling models, and Bolton compound fouling models. RIS analysis indicated that cake layer resistance was the dominant contributor to total filtration resistance for all membranes, while the incorporation of silver ions significantly reduced the proportion of irreversible fouling. Hermia model fitting suggested that cake filtration was the predominant fouling mechanism during most filtration stages, whereas intermediate blocking became more significant after repeated operation. However, the relatively lower fitting accuracy of the Hermia models highlighted their limitations in describing the simultaneous occurrence of multiple fouling mechanisms in MBR systems. In contrast, Bolton compound models combining cake filtration with pore-blocking mechanisms showed excellent agreement with experimental data (R2 > 0.99), confirming the inherently multi-mechanistic nature of membrane fouling. Overall, the results demonstrate that single-mechanism fouling models are insufficient for accurately representing fouling dynamics in MBR systems, while compound models provide superior predictive capability and deeper mechanistic insight. This study highlights the importance of integrating advanced fouling modeling with membrane material development and demonstrates that silver-based antibacterial PVC/TPU membranes promote surface-dominated and more reversible fouling behavior. These findings contribute to improving the prediction and control of membrane fouling, thereby supporting the development of more stable and efficient MBR systems for wastewater treatment.