Evaluation of N-methylpyrrolidone bio-mineralization mechanism and bacterial community evolution under denitrification environment

With the increasing discharge of wastewater produced from industrial manufacture, the accumulation of recalcitrant and toxic contaminants such as N-methylpyrrolidone (NMP) in ecosystem has raised concerns about their environmental implication. In this study, a denitrification bioreactor was developed and continuously performed for 245 days to realize simultaneous NMP mineralization and nitrate reduction. During long-term experimental period, the approximately 3000 mg L−1 NMP could be thorough degraded along with high nitrate removal efficiency (>97%), the dominant bacteria populations responsible for NMP hydrolysis (Paracoccus, Brevundimonas and Pseudaminobacter) and microbial denitrification (Paracoccus, Hyphomicrobium, Pseudomonas and Pseudoxanthomonas) as well as electron transport (Shewanella) were significantly enriched under denitrification condition. Further enzymatic activity assay revealed the catalytic activities of N-methylhydantoin amidohydrolase (NMA) and succinate dehydrogenase (SDH) were largely enhanced under denitrification environment, indicating that microbial denitrifying distinctly promoted the hydrolysis and mineralization of NMP, which was rather conducive for better NMP removal capacity and long-term stability. In conclusion, this research verified the feasibility of denitrification promoting N-heterocyclic compounds mineralization process and provided theoretical guidance for the engineering application of biodegradation coupled with denitrification treatment.