Novel photocatalytic bacteria-algae coupling system mediated by g-C₃N₄ nanoparticles: Effects of microbial ratio on...

This study explored symbiotic interactions within a graphitic carbon nitride (g-C₃N₄)-enhanced bacterial-algal system for advanced wastewater treatment by examining the effects of varying bacterial-algal ratios (10:1, 5:1, and 1:1) on nutrient removal, microbial aggregation, and community dynamics in sequencing batch reactors. The 1:1 ratio (R3) exhibited optimal performance, achieving highest chemical oxygen demand removal (98.7 %) and ammonium nitrogen removal (92.4 %), alongside increased algal biomass. R3 enhanced microbial aggregation via elevated extracellular polymeric substances (EPS, 80.2 mg/g SS), reduced electrostatic repulsion. Microbial profiling revealed higher abundances of Proteobacteria (37.6 %) and Cyanobacteria (9.1 %), synergistically enabling nitrogen assimilation and integration of photocatalytic and biological degradation pathways. The balanced ratio improved dissolved oxygen regulation via algal photosynthesis, while EPS helped mitigate g-C₃N₄-induced oxidative stress. These findings provide mechanistic insights for the strategic optimization of bacterial-algal consortia in photocatalytically enhanced wastewater treatment systems, with implications for the development of sustainable and energy-efficient water remediation technologies.