Simultaneous removal of nitrate, zinc, and bisphenol A by an iron-modified biochar composite mycelial pellet bioreactor: Optimization and microbial mechanisms

In this study, iron-modified biochar composite mycelial pellets (CMPs) were utilized to immobilize the Fe 2 + oxidizing denitrifying bacterial strain Zoogloea sp. FY-6, with the aim of simultaneous removal of nitrate (NO 3 - -N), zinc (Zn 2+ ) and bisphenol A (BPA). Under conditions of 8 h hydraulic retention time (HRT), pH 7.0, and influent concentrations of 25.0 mg L −1 NO 3 - -N, 1.0 mg L −1 Zn 2+ , and 1.0 mg L −1 BPA, the bioreactor reached its best performance, with NO 3 - -N, Zn 2+ , and BPA removal efficiencies of 87.2%, 92.4%, and 94.4%, respectively. The experimental results demonstrated that the addition of iron-modified biochar can enhance denitrification. The removal of Zn 2+ and BPA was primarily attributed to adsorption and coprecipitation mediated by biogenic precipitates formed during bioreactor operation. Through high-throughput sequencing and metabolic pathway analysis, it was found that Bacteroidia , Alphaproteobacteria , and Clostridia were key contributors to denitrification and contaminant degradation. Metabolic pathway analysis further elucidated the synergistic relationships between these microbial communities and the iron-modified biochar. This research provides new insights into the treatment of complex industrial wastewater using multifunctional microbial systems. • Strain FY-6 and Fe-modified biochar were immobilized on composite mycelium pellets. • The oxidation of iron enhanced the denitrification process. • Fe-modified biochar loading exhibited optimal removal performance. • Zn and BPA were removed by biologically induced precipitation and adsorption.