Rotten banana powder: A waste-recycling alternative for external carbon source

Although rotten banana (RB) has been proved as a superior carbon source for denitrification, how to maintain its effectiveness while reduce the depressing transportation expenses deserves for more considerations. In this study, a modified carbon source-RB powder (RBP) was prepared and utilized for treating nitrate in wastewater. Results indicated that RBP, equipped with rapid organic release and low residual properties, could achieve a maximum nitrate removal rate of 96.79% and inapparent nitrite accumulation with a denitrification rate higher than RB slurry. Supplementing RBP improved the long-term stability of sludge in the denitrification system while the dosage served as a promoting factor towards sludge dewatering performance but a limiting factor towards system stability. The breeding of unique bacteria was easily altered by increasing nitrate load, contributing to the combined denitrification via various microorganisms. Meanwhile, the phyla and genera related to denitrification and organic fermentation were effectively enriched by improving RBP dosage. Compared with RB slurry and sodium acetate, less denitrification cost would be obtained by RBP when the usage amount respectively exceeded 7.31 tons and 228.18–555.56 tons. All the results demonstrated that RBP would be selected as a more cost-efficient choice for denitrification in view of practical applications.