Dissolved oxygen alters the microbial interactions of anammox consortia in PN/A process

Abstract

The main purposes of this study were to investigate the effects of different dissolved oxygen (DO) conditions (0.3 and 1.0 mg/L) on the microbial interactions in the partial nitrification/anammox (PN/A) process. The results indicated that the high concentration of DO (1.0 mg/L) significantly inhibited the activity of anammox bacteria (AnAOB) while enhanced the activity of nitrite oxidation bacteria (NOB) in the PN/A reactor. 1.0 mg/L DO promoted the abundance of NOB (such as Nitrospira) and some heterotrophic microorganisms (e.g., SBR1031 and OLB13), while decreased ammonia oxidizing bacteria (AOB, e.g., Nitrosomonas) and AnAOB (Ca.Brocadia and Ca.Kuenenia). 1.0 mg/L DO concentration driven a larger and more complex network with increased percentage of positive links, which might be a strategy for microbes to resist the adverse environment. Furthermore, the subnetworks of anammox bacteria and Nitrosomonas became smaller and simpler, whilst the subnetworks of heterotrophic bacteria (SBR1031) were more complex and connected. The decreased activity and abundance of AnAOB, together with the shifts of microbial interactions might result in the deterioration of nitrogen removal under 1.0 mg/L DO. This study provides a relatively comprehensive perspective for us to understand the effects of DO on the microbial interactions in the PN/A system.