High-rate nitrogen removal by partial nitritation/anammox with a single-stage membrane-aerated biofilm reactor

In this study, a membrane aerated biofilm reactor (MABR) coupled partial nitritation/anammox (PN/A) system was established for high-rate nitrogen removal. Results showed that the nitrogen removal efficiency of 90.34% was finally obtained when influent ammonia increased from 150 mg L^-1 to 300 mg L^-1. Based on the fluorescence spectroscopy technology, the raised hydrophobicity tryptophan in extracellular polymeric substances (EPS) promoted biofilm formation and bacteria aggregation. 16S rRNA gene amplicon sequencing revealed that the relative abundance of AOB and AnAOB was also enhanced by ammonia (Nitrosomonas and Candidatus Brocadia increased by 6.02 % and 10.06 % in biofilm, respectively), which further facilitated nitrogen removal efficiency. Furthermore, the key functional genes involved in partial nitritation and anammox, especially hao and nirK, up-regulated by 1.31 and 1.26 times, respectively, accelerating the electron generation and consumption. Therefore, raising influent ammonia content intensified microbial electron transfer behavior and high-rate nitrogen metabolism.