Simultaneous removal of nitrogen, Cu2+, and bisphenol A in a hydrogel-biochar-AQDS immobilized bioreactor with added bicarbonate: Performance and metagenomic insights.

As the complexity of industrial wastewater pollution continues to increase, the simultaneous removal of nitrogen, metal contaminants, and persistent organic pollutants under low carbon conditions has become a key challenge for biological treatment systems. To address the operational instability and dependence on carbon sources observed in immobilized systems when exposed to copper (Cu2+) and bisphenol A (BPA), the Pseudoalteromonas japonicus strain LY0623 was integrated into a hydrogel-biochar-AQDS composite carrier to construct a multifunctional immobilized biofilm system. Notably, under conditions containing only NaHCO3, the R4 system achieved an NH4+-N removal rate of 89%. Under conditions where Cu2+ and BPA coexist, the R4 system achieved removal of NH4+-N (89%), NO3--N (100%), Cu2+ (85%), and BPA (88%). Sediment characterization confirmed that Cu2+ was immobilized through adsorption, complexation, and microbiologically induced carbonate precipitation (MICP). Metagenomic analysis further indicated that the Pseudomonadota phylum remained the dominant phylum, while functional pathways associated with inorganic carbon assimilation, HNAD nitrogen metabolism, endogenous carbon transformation, biomineralization, electron transfer, and aromatic compound degradation were preserved. By combining ammonia oxidation driven energy production, inorganic carbon utilization, redox mediated processes, and biomineralization, this study provides a highly promising low carbon strategy for treating industrial wastewater containing mixed pollutants.