Enhanced Organic Fouling Control and Energy-Saving Strategies in PVDF Hollow Fiber Membrane Ultrafiltration via...

Micro-nanobubbles (MNBs) aeration has been widely reported as an effective approach for membrane fouling mitigation. However, their optimal operation in polymeric hollow fiber membrane (HFM) systems remains unclear. In this study, the antifouling performance of MNB-assisted ultrafiltration was systematically investigated using a PVDF-HFM, with particular emphasis on release pressure and intermittent aeration strategy. Increasing the release pressure to 0.60 MPa produced smaller and more concentrated bubbles, significantly alleviating membrane fouling. A distinct intermittent-aeration window was observed, in which a 15 min interval achieved the best overall performance, with a rejection efficiency of 75% and a cleaning efficiency of 93%, approaching that of continuous aeration. Longer intervals resulted in rapid deterioration in fouling control, indicating insufficient bubble replenishment. Compared with continuous operation, the optimized intermittent mode maintained comparable membrane performance while reducing energy consumption by approximately 50%, demonstrating a clear advantage in energy efficiency. Importantly, the optimal intermittent interval for PVDF-HFM (15 min) differs from that reported for ceramic membranes (30 min), highlighting that the performance of intermittent MNB aeration is not universal but strongly dependent on membrane properties. This shift in optimal interval is attributed to differences in surface wettability, structural flexibility, and local hydrodynamic conditions, which collectively influence bubble retention, interfacial shielding, and foulant detachment.