Enhanced 4-bromophenol removal and mineralization in bio-photodegradation system: The key role of microbial interactions.

Halophenols are common industrial monomers with high toxicity, posing a serious threat to the ecological environment and human health. In this study, we achieved enhanced bio-photodegradation of 4-bromophenol (4-BP, a representative halophenol) using B-doped g-C₃N₄/BiVO₄ as a photoexcited semiconductor. The Z-scheme heterojunction of B-doped g-C₃N₄/BiVO₄ endowed photogenerated electron-hole pairs with stronger redox capacity; notably, photoelectrons played a vital role in accelerating 4-BP degradation. They not only facilitated the generation of superoxide radical anions (effective active species for 4-BP photodegradation) but also served as critical electron donors for microbial debromination. In order to explore the significance of microbial interactions in 4-BP bio-photodegradation, carriers with different thicknesses were employed to construct bio-photodegradation systems. Results from these systems revealed that thicker carriers provided sufficient attachment sites for microbial enrichment, which promoted more frequent microbial interactions to accelerate 4-BP bio-photodegradation. Microbial community analysis confirmed that increased attachment sites were beneficial for the enrichment of functional species (related to 4-BP biodegradation and electron transfer), and upregulated expression of related functional genes was also observed according to Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) analysis. Microbial co-occurrence networks analysis indicated that positive interactions of different species were the important reasons for enhanced 4-BP bio-photodegradation. A possible mechanism of 4-BP bio-photodegradation was proposed based on the above analysis.