Evaluation of wood vinegar as a green carbon source for heterotrophic nitrification and aerobic denitrification process from performance, mechanism and potential

Carbon sources as energy sources and electron donors are essential for the nitrogen removal efficiencies of heterotrophic nitrification and aerobic denitrification (HNAD) process. However, conventional carbon sources from the chemical industry face issues of low stability of biological treatment systems and increased indirect carbon emissions in practical applications. Encouragingly, wood vinegar, a by-product of biomass pyrolysis process, promises to address these concerns. Herein, we investigated the potential of wood vinegar for green composite carbon source in HNAD process from multiple perspectives by establishing different microcosms. Regular monitoring results showed that wood vinegar-fed microcosms had the optimal cost-effectiveness with a C/N ratio of 7, and total nitrogen and COD removal efficiencies of up to 85.0 % and 93.4 % respectively. Furthermore, wood vinegar significantly improved the species diversity and optimized the microbial community structure compared to traditional carbon sources, strengthening the stability and resistance of the microcosm. Meanwhile, the enrichment analysis of key genes and enzymes indicated that both carbon and nitrogen metabolism were enhanced obviously, and the wood vinegar as a composite carbon source was expected to overcome the defects of traditional carbon sources, better balance the nitrification and denitrification capabilities. Importantly, the introduction of wood vinegar does not present a risk of secondary contamination and contributes to carbon reduction in the water treatment field. All indications are that wood vinegar as a green composite carbon sources can enhance wastewater treatment system stability and efficiency, and provide a viable strategy for promoting more sustainable wastewater management.