A single-stage membrane aerated biofilm reactor achieving the combination of partial nitritation/anammox and enhanced biological phosphorus removal

Efficient biological nutrient removal in carbon-limited wastewater poses a challenge for municipal wastewater treatment plants. In this study, the combination of partial nitrification anammox (PN/A) and enhanced biological phosphorous removal (EBPR) was achieved in a single-stage membrane aerated biofilm reactor (MABR). The process demonstrated simultaneous removal of NH4+-N (92.61 %), TN (82.13 %), and TP (70.00 %). Isotopic tracing tests using 15N revealed that anammox contributed to 64.9 % of TN removal. The formation of counter-diffusion biofilm in the MABR greatly enriched functional microorganisms, with the predominant species of Nitrosomonas (2.41 %), Candidatus Brocadia (1.47 %) and Dechloromonas (0.55 %). Through genome-centered analysis, hydroxylamine (NH2OH)-mediated ammonia oxidation was identified as the key process for Candidatus Brocadia pituitae in the counter-diffusion biofilm in MABR. It can be hypothesized that the bidirectional provision of NH2OH by ammonia oxidizing bacteria in the inner layer (with high DO) of the biofilm and the denitrifiers in the outer layer (with high organics) cooperated with anammox to achieve efficient nitrogen removal. Additionally, PAOs (Dechloromonas sp.) played versatile roles in nitrogen and phosphorus cycling in the carbon-limited environment.