Salinity is a key environmental factor for the successful application of anammox technology in wastewater treatment, because it impacts the activity and the community structure of anammox bacteria. In this study, the changes in activity and population shifts of an anammox system response to the elevated salt stress (0, 5, 10, 20, 30 and 40 g NaCl/L) were studied.
The results show that the anammox reactor performed effectively even at 30 g NaCl/L salinity after an appropriate acclimatization. The nitrogen removal rate maintained at 0.28 g N L-1d-1 with the nitrogen removal efficiency of 76%, though the high environmental salinity might inhibit the anammox growth in the long-term operation. 16S rRNA high-throughput sequencing results revealed that Ca. Brocadia, Ca. Jettenia and Ca. Kuenenia were the dominant anammox bacteria at all salinities. Ca. Brocadia and Ca. Jettenia were quite sensitive to salinity, and 5 g NaCl/L dosing could cause a sharp decline in their abundance. Nevertheless, these three anammox genus finally survived in the system with a steady specific anammox activity of 0.13 g N g VSS-1d-1. Specially, a novel cluster, Brocadiaceae_unclassified, which possibly belongs to anammox bacteria, became the dominant genus at the salinity over 20 g NaCl/L and likely contributed partially to the nitrogen removals. Our findings elucidated the inherent link between community dynamics and anammox system performance and stability under salty environment, and proved that anammox technologies can be an effective technology for treatment of saline ammonia-rich wastewater.