Microbial community dynamics and performance of simultaneous anammox and denitrification (SAD) process at varying substrate loadings during long-term operation

The simultaneous anammox and denitrification (SAD) process has attracted more and more attention due to its low energy consumption and high-efficiency, but its optimal operating conditions and the interspecies in-teractions between the main functional microorganisms anaerobic ammonia oxidation bacteria (AnAOB) and denitrifying bacteria (DNB) have not been fully elucidated. In this study, SAD was achieved by enriching DNB through the addition of sodium acetate to anammox granular sludge. Furthermore, the pollutant removal effect and the composition of the main functional microbial community under different organic loads were investigated by manipulating the influent C/N ratio. The results indicated that the reactor achieved the highest total nitrogen removal efficiency of 89.05% at a C/N ratio of 1 and the activity of AnAOB was inhibited on a higher C/N ratio, leading to the deterioration of effluent quality. Candidatus_Brocadia was the dominant genus of AnAOB, reaching a maximum relative abundance of 0.49% at a C/N ratio of 1. DNB was also significantly enriched after the addition of sodium acetate, and the synergistic effect of the two functional bacteria contributed the simultaneous nitrogen and carbon removal of the SAD process.

Automated summary

The simultaneous anammox and denitrification (SAD) process was achieved by enriching denitrifying bacteria (DNB) through the addition of sodium acetate to anammox granular sludge. The study investigated the pollutant removal effect and the composition of the main functional microbial community under different organic loads by manipulating the influent C/N ratio. The results showed that the highest total nitrogen removal efficiency of 89.05% was achieved at a C/N ratio of 1, and Candidatus_Brocadia was the dominant genus of AnAOB.