Improved performance of simultaneous nitrification and denitrification via nitrite in an oxygen-limited SBR by alternating the DO.

Graphical abstract Highlights • SND via the nitrite pathway was achieved when the DO was 0.7 ± 0.1 mg/L. • A novel short nitrification strategy was achieved by alternating the DO content. • The bacterial communities and metabolic functions of sludge were evaluated. • The relative content of denitrifying bacteria increased under low DO conditions. • Enzymes involved in nitrification and denitrification increased when DO decreased. Abstract In this study, the performance of simultaneous nitrification and denitrification via nitrite was investigated by alternating the dissolved oxygen (DO) concentration in a sequencing batch reactor with the DO-control area and the non-control area. In addition, bacterial communities and their metabolic functions were analyzed by high-throughput sequencing technology and phylogenetic investigation of the communities by reconstruction of unobserved states (PICRUSt). The removal efficiencies of NH 4 +-N and total nitrogen via the nitrite pathway were 97.91 ± 2.04% and 72.28 ± 2.23%, respectively, by maintaining low DO levels (0.7 ± 0.1 mg/L) in the DO-control area. PICRUSt analysis showed that the metabolic potential of the bacterial community for amino acids, nucleotides, coenzymes and inorganic ions decreased, while the relative abundance of key enzymes involved in nitrification and denitrification, and the relative population of denitrifying bacteria increased when the DO decreased from 1.2 ± 0.2 mg/L to 0.7 ± 0.1 mg/L. [ABSTRACT FROM AUTHOR]