LAUSR

The rapid start-up of Partial denitrification (PD; nitrate to nitrite) was investigated based on the analysis of microbially driven mechanism of nitrite accumulation mediated by Dissolved organic matter (DOM) in this study. The nitrate to Nitrite transformation ratio (NTR) > 90% and effluent nitrate < 5 mg/L were achieved in 17 days by feeding with lower nitrate of ~ 35 mg/L and removing the idling period. And the enhanced nitrite accumulation when applying the above strategy is related to the decreased utilization of the aliphatic DOM during nitrite reduction process. Additionally, the rapid enriched Thauera and OLB13 (37.21%) and inhibited norank_f__Blastocatellaceae (2.86%), and the increased disparity (2.0-fold) between the genes involved in nitrite generation (e.g., narH) and for nitrite reduction (e.g., nirK) jointly contributed to PD start-up. While the genes (e.g., DLD) related to producing electrons from aliphatic DOM also up-regulated by 0.1-fold, which led to the increased nitrate removal and NTR.