Regenerated end-of-life membranes outperform in full-scale MBRs: A long-term study on fouling evolution and...

Polymeric membranes in membrane bioreactors (MBR) inevitably reach end-of-life (EOL) and are typically disposed of via landfill or incineration, raising sustainability concerns. Membrane regeneration offers a sustainable route for membrane industry, while its feasibility and long-term fouling behavior in full-scale wastewater treatment systems remain unexplored. Herein, 1600 m² of EOL membranes were regenerated at engineering scale and then operated in a full-scale MBR, with chemically cleaned EOL membranes as the control. Over one-year operation, regenerated membranes exhibited more stable water production and superior fouling resistance. These changes arose from their enhanced water permeance and restored surface hydrophilicity after regeneration, which weakened foulant-membrane interactions and mitigated fouling accumulation. The organic recoverable fouling content in regenerated membranes decreased by 66.8%, while Ca content was reduced by 40.7% compared to the control. Regarding irrecoverable fouling, the reduced HA and Ca-associated deposition in regenerated membranes weakened cation bridging. Mechanistic analyses revealed a transition from a compact Ca/Mg-bridged organic network in the EOL membrane to a weakly coordinated fouling structure after regeneration. Furthermore, the membrane regeneration strategy reduced the annualized economic cost by 38.6% and carbon emissions by 25.5%, demonstrating its technical feasibility and sustainability advantages for full-scale MBR applications.