Optimizing denitrification with volatile fatty acids from hydrolysis acidification-treated domestic wastewater: Comparative effects of nitrate and nitrite using immobilized biofiller

By embedding immobilized biofiller, 100% denitrification efficiency was achieved with nitrate or nitrite as electron acceptors utilizing volatile fatty acids (VFAs) from domestic wastewater after hydrolysis acidification. The consumption patterns of VFAs by functional bacteria and differences in nitrogen metabolic gene expression were thoroughly analyzed. Total consumption of acetic and propionic acids with >95% VFAs utilization was achieved utilizing nitrate, whereas the consumption of butyric and valeric acids was enhanced utilizing nitrite. Denitrification-related genes were all upregulated, particularly nosZ, indicating systemic N₂O emission reduction potential. Electron acceptor changes dynamically shifted microbial dominance from Thauera (19.4%) to Thiobacillus (7.2%). These results provide valuable insights into the adaptability and ecological niche characterization of denitrifying bacteria, contributing to improving nitrogen removal efficiency, optimizing carbon source utilization, and reducing sludge production.