Achieving efficient anammox contribution and the enrichment of functional bacteria in partial denitrification/anammox system: Performance, microbial evolution and correlation analysis.

[Display omitted] • PD/A reactor achieved 87.8 % nitrogen removal with anammox contribution of 100 %. • 15N isotopic tracing technology revealed PD was the prerequisite for anammox. • Bacillus (27.27 %) and Ca.Brocadia (7.09 %) were enriched at NO 3 −-N: NH 4 +-N of 1.0. • Low temperature was beneficial to the enrichment of Thauera and Ca.Jettenia. The primary challenge of applying partial denitrification/anammox (PD/A) to municipal wastewater treatment lied in the enrichment of functional bacteria with a considerable autotrophic nitrogen removal performance. The results showed influent NO 3 −-N: NH 4 +-N, reaction time and temperature would influence anammox nitrogen removal contribution. 15N isotopic tracing technology further revealed the average anammox contribution rate was up to 94.8 %. Extending reaction time was an effective measure to improve simultaneously PD and anammox activity. Microbial community indicated partial denitrifying bacteria (Bacillus) and anammox bacteria (Candidatus Brocadia) were enriched with abundance of 27.27 % and 7.09 % at NO 3 −-N: NH 4 +-N of 1:1. The correlation analysis showed that NO 3 −-N: NH 4 +-N ratio played the positive role for Bacillus enrichment, and low temperature was favorable to the enrichment of Thauera and Candidatus Jettenia. Overall, this study demonstrated the reasonable operational strategy would strengthen anammox contribution and facilitate enrichment of functional bacteria. [ABSTRACT FROM AUTHOR]