[Microbial Community of Granular Sludge in an ANAMMOX-EGSB Reactor Under Saline Conditions]

High-throughput sequencing technology was used to investigate changes in the microbial community in granular sludge under salinity conditions of 0, 15, and 30 g·L^-1 in an ANAMMOX-EGSB reactor under stable operation. The study found that when the influent salinity was increased to 15 g·L^-1 and 30 g·L^-1, the nitrogen removal performance of the reactor decreased slightly, but was restored with the extension of the running time. After the performance of the reactor became stable, the abundance of the ANAMMOX bacteria under the three salinity conditions was 10.33%, 20.90%, and 35.87%, of which Candidatus Kuenenia was the dominant genus. Planctomycetes, Proteobacteria, and Chloroflexi accounted for a high proportion in the granular sludge, and their cumulative abundance exceeded 80%, making them the dominant phyla of the reactor. Under saline conditions, the abundance of the Planctomycetes bacteria increased, the abundance of the Proteobacteria bacteria decreased, and the abundance of the Chloroflexi bacteria was relatively stable. Electron microscopy showed a large number of filamentous bacteria and extracellular polymers were present on the surface of the granular sludge under saline conditions. The increased abundance of the denitrifying bacteria enhanced the cooperative denitrification, the presence of aerobic microorganisms and denitrifying bacteria facilitated the maintenance of anaerobic conditions inside the reactor, and the increased abundance of Chloroflexi and Bacteroidetes was beneficial to maintain the stability of the granular sludge structure. These results showed that the ANAMMOX bacteria could be adapted to saline conditions by acclimation, and that the associated bacteria provided support for the function of the ANAMMOX bacteria under saline conditions.