An anaerobic-applicable Bi2MoO6/CuS heterojunction modified photocatalytic membrane for biofouling control in anammox MBRs: generation and contribution of reactive species

The anaerobic (anoxic) environment in anaerobic membrane bioreactors (AnMBRs) largely limits the antifouling application of aerobic-applicable photocatalysts, calling for preparation of anaerobic-applicable photocatalytic membranes, and exploration of generation and contribution mechanisms of reactive species under anaerobic (anoxic) condition. Herein, novel visible-light photocatalytic membranes (B2) were prepared by modifying pristine membranes (B0) with hollow flower-like Bi2MoO6/CuS heterojunctions to explore production and antifouling function of reactive species in anammox MBRs. During 157-d operation under waterproof lights irradiation, the average fouling cycle of B2 extended to 228.5% of B0, while their total nitrogen removal efficiencies (TNRE) were comparable and maintained at 0.85–0.9. The energy against the membrane fouling resistance were saved about 18.4% by filtering with B2. By adding scavengers of reactive species in flux recovery tests, photocatalytic generated ·OH, h+ and e− were testified to be responsible for the alleviated membrane fouling, whereas ·OH (rather than ·O2−) was qualitatively and quantitatively proved to be the key reactive oxygen species produced by B2. Compared with B0, the degradation and inactivation capabilities of reactive species on B2 brought about 47.7% lower organic foulant by decomposing protein, polysaccharide and lipid; and contributed to 76.1% lower total bacteria, 51.0% higher necrotic cells, and 29.1% higher esterase-inactivated cells. Furthermore, the photocatalytic membranes showed satisfactory stability and biocompatibility, providing powerful support for their long-term usage in MBRs as a low-carbon and eco-friendly strategy. The systematic insights into reactive species contribution for fouling alleviation by the anaerobic-applicable photocatalytic membrane offer valuable instructions for extended antifouling application of photocatalysis in AnMBRs.