Mainstream partial Anammox for improving nitrogen removal from municipal wastewater after organic recovery via magnetic separation.

[Display omitted] • Mainstream partial Anammox was achieved after organic recovery in a new concept WWTP. • Anammox contributed 23.6% of TN removal, increasing TN removal efficiency by 15.0% • A shift from nitrification/denitrification to partial Anammox was observed. • Candidatus Brocadia was the dominant AnAOB in the double-sludge N removal system. Total nitrogen (TN) removal from municipal wastewater after organic recovery is challenging because of the low ratio of chemical oxygen demand (COD) to TN. Anaerobic ammonium oxidation (Anammox) is promising because it has no organic requirement, but its performance in treating effluents following COD captured remains unclear. This study used mainstream partial Anammox to remove nitrogen from effluent following magnetic separation within a continuous-flow anoxic–oxic reactor. Compared with traditional nitrification and denitrification, partial Anammox increased TN removal efficiency by 15.0% and contributed 23.6% of TN removal. Quantitative polymerase chain reaction revealed that the copy number of the Anammox gene (hzsB) increased substantially, while those of the nitrite oxidation (nxrA) and denitrification (narG and nirS) genes decreased. High-throughput sequencing identified Candidatus Brocadia as the dominant genus of anaerobic ammonium-oxidizing bacteria. These findings demonstrate the effectiveness of mainstream partial Anammox for treating COD-captured effluents and its potential in municipal wastewater treatment. [ABSTRACT FROM AUTHOR]