Volatile fatty acids from food waste as external carbon Sources: Denitrification Efficiency, microbial Pathways, and Techno-Economic assessment.

Volatile fatty acids (VFAs) derived from the anaerobic digestion of food waste were systematically evaluated as an alternative external carbon source for wastewater denitrification. An optimized segmented dosing strategy significantly enhanced VFA denitrification performance, achieved an 89.16 % total nitrogen removal rate, demonstrated superior carbon utilization and minimized nitrite accumulation. Kinetic analysis revealed a denitrification rate of 7.36 mg N/(g VSS·h) and potential of 0.22 g N/g COD for the VFA system, both of which surpassed those of the methanol and glucose systems. Microbial community profiling indiacted the enrichment of functional denitrifiers (Azoarcus and Pseudomonas) and diverse metabolic pathways. Engineering-scale scenario analysis showed a > 70 % reduction in long-term carbon costs, an internal rate of return of 8.5 %. Monte Carlo simulations (n = 100,000) confirmed economic robustness. These findings demonstrate that VFAs represent a technically feasible, economically viable carbon source and a promising foundation for sustainable wastewater treatment methodologies.