Insight into nitrogen removal performance of anaerobic ammonia oxidation in two reactors: Comparison based on the aspects of extracellular polymeric substances and microbial community

Abstract

Anaerobic ammonium oxidation (Anammox) is expected to play a promising role in treating low C/N ratio wastewater. In this study, nitrogen removal performance and the effects of extracellular polymeric substances (EPS) on anammox activity were investigated in two different reactors, followed by analysis of 16S rRNA high-throughput sequencing. A sequencing batch reactor (SBR) and an up-flow anammox sludge blanket reactor (UASB) operated for 133 days, with total nitrogen removal efficiencies of 82.09 ± 4.76% and 87.91 ± 2.59% in the phase 3, respectively. The EPS concentration in UASB was about 1.6 times higher than that in SBR. Also, in the batch tests, especially the anammox-EPS of UASB (AU-EPS) additions contributed to better nitrogen removal capability for anammox bacteria (AnAOB). The relative abundance of AnAOB in UASB was observed to reach 19.68% in the end, accounting for a relatively high degree in the whole community. In SBR, the effluent NH4+-N concentration increased when increasing the substrate concentration, followed by the decrease of the relative abundance of AnAOB. Thus, the different feeding strategies would lead to different granulation styles, further influencing the activity and stability of anammox system. This research aims to get a better understanding of the different mechanisms associated with AnAOB enrichment strategies.