In-situ revitalizing end-of-life MBR membranes via a curtain-type dynamic membrane process

Membrane bioreactors (MBR), an industrial mainstay with over 15,000 installations worldwide, face severe sustainability challenges from frequent membrane replacement, generating over 500,000 tons of waste annually. Dynamic membranes, a promising alternative, are impeded in large-scale implementation by inherent issues of conventional flat-sheet designs, such as uneven flow distribution and performance instability. Herein, we propose a strategy that directly upcycles end-of-life hollow-fiber MBR membranes as substrates for curtain-type dynamic membranes (CTDMs). The curtain-type substrate layer rapidly forms a biofilm and attains stable effluent quality (turbidity <5 NTU) within 10 minutes. Exposing only 5% of the internal substrate surface for CTDM fabrication restores performance comparable to that of new MBR membranes while meeting discharge standards. Life-cycle assessment reveals a 1,070-fold reduction in carbon emissions (0.0025 vs. 2.67 kg CO₂ m^-2) and 99.9% lower environmental costs (0.0072 vs. 7.81 USD m^-2) compared to traditional membrane replacement. Scaling up this approach could mitigate 441 kt of CO₂ in China alone by 2035. This approach concurrently addresses two global crises, accumulating plastic waste from spent membranes and escalating energy costs of water treatment.