Directing algal-bacterial interactions and system function with g-C₃N₄ under photostimulation

The effective treatment of wastewater, particularly those with high carbon and nitrogen content, remains a significant environmental challenge. Traditional methods often suffer from inefficiency and high energy consumption, underscoring the need for innovative, sustainable solutions. In this study, we explored the use of graphitic carbon nitride nanoparticles (g-C₃N₄-NPs) to enhance the performance of algal-bacterial systems under visible light. By adding varying concentrations of g-C₃N₄-NPs (0, 50, and 100 mg/L), we investigated their effects on wastewater treatment efficiency, microbial community dynamics, and system stability. The results showed that the addition of 50 mg/L g-C₃N₄-NPs (R2 system) significantly improved nutrient removal, particularly in chemical oxygen demand and total nitrogen, by promoting algal growth, increasing extracellular polymeric substance secretion, and enhancing microbial aggregation. Mechanistic studies revealed that g-C₃N₄-NPs facilitated electron transfer and optimized microbial interactions, which stabilized the system and boosted overall performance. This work is innovative as it demonstrates the critical role of g-C₃N₄-NPs in fostering a balanced algal-bacterial ecosystem, leading to efficient wastewater treatment with minimal energy input. These findings offer new insights into the potential of nanomaterials in environmental biotechnology, providing a sustainable approach to improving wastewater treatment systems.