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

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 NH₄⁺-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.