Abstract
This study investigates the feasibility of utilizing banana peel leachate (BL) treated with different concentrations of alkali solutions as carbon sources in denitrification systems and its nitrogen-removal performance under varying nitrogen load conditions. The research discovered that banana peel extract treated with 0.01 mol/L NaOH (BL-10) exhibited the highest chemical oxygen demand (1903 mg/L). In shaking flask experiments, BL-10 demonstrated the best nitrate-nitrogen removal efficiency (96.87%) in the alkali-treated group. The denitrification efficiency was minimally affected by changes in the initial nitrate-nitrogen concentration. Analysis of the microbial community composition revealed that the phyla Proteobacteria, Patescibacteria, and Bacteroidota constituted the predominant bacterial groups within the system. Further functional analysis of bacteria revealed an increase in the abundance of enzymes-encoding genes related to denitrification and carbon metabolism in BL-10. Overall, alkali-treated banana peel leachate shows potential as a viable carbon source for denitrification in short-term batch assays.