Novel self-assembled nanocellulose coating on microfiltration membranes for pathogen inactivation and fouling mitigation

Fouling by natural organic matter (NOM) and biofilm is a critical challenge in membrane technologies for wastewater treatment. Superior hydrophilicity of nanocrystalline cellulose (NCC) modified on membranes renders antifouling properties; however, NCC suffers from aggregation during processing and has limited antibacterial and anti-biofouling performance. Here, we developed a novel sterically stabilized nanocrystalline cellulose (SNCC) layer functionalized on commercial microfiltration (MF) membranes that can inactivate bacteria and mitigate fouling. SNCC was synthesized from the periodate oxidation of cellulose with highly accessible and enriched aldehyde groups at amorphous rod ends. This enabled in-situ self-assembly via hemiacetal bonding into a stable and homogeneous layer on polydopamine (PDA)-coated MF membranes, confirmed by comprehensive characterization results. The SNCC-membranes had improved hydrophilicity and water permeability, resulting in a 7.5-fold lower NOM fouling. Upon contact, SNCC-membranes achieved up to 91 % and 83 % inactivation of E. coli and B. subtilis. During P. aeruginosa biofilm fouling and backwashing cycles, the SNCC-membranes achieved 90–100 % flux recovery compared to the control (40–82 %), by suppressing biofilm thickness (by ~1.9 fold) and inactivating cells in biofilm (by 46-fold). Long-term biofouling test (108 h) and a 24-cycle fouling/backwashing test both showed 3–7 fold slower flux decline than the control. Furthermore, a 35-day exposure to various pH conditions and chlorine showed desirable coating stability and a 2.4-fold longer lifetime than the control. Finally, an initial technoeconomic analysis suggested a near 60 % annual OPEX reduction by adopting SNCC membrane coating. This study presents a novel, cost-saving, and sustainable antifouling solution for resilient membrane-based wastewater treatment.