From acetate-driven partial denitrification (PD) to N-Methylpyrrolidone-driven PD: Microbial community, metabolic pathway and functional genes.

With the rapid development of the new energy industry, the wastewater discharged from battery production industries has increased significantly, in which N-Methylpyrrolidone (NMP) have aroused widespread attention. It is valuable to develop low-cost biological methods for NMP containing wastewater treatment. In this study, an NMP-driven PD system was acclimated in an sequencing batch reactor (SBR) by gradually replacing the sodium acetate with NMP. The nitrate-to-nitrite transformation ratio (NTR) of the acclimated PD sludge was stabilized around 60 % and reached up to 68.1 %.The TOC removal was maintained above 90 %, and the NO-N reduction reached up to 96.7 %. The relative abundance of denitrifying bacterium Paracoccus increased during domestication (from 0.11 % to 9.38 %), and the abundance of NMP metabolism-related genes (hyuA, hyuB, mao, and gabD) also increased significantly. Moreover, the contribution of Paracoccus to NMP metabolism-related genes gradually increased. It suggests that Paracoccus may play a major role in this system. In conclusion, this study verified the feasibility of NMP as a carbon source to drive PD process to achieve NO-N accumulation, and provided a novel strategy for nitrogen removal of battery wastewater.