Enrichment of Nitrosocosmicus-AOA in situ and their vertical distribution characteristics in aerated biofilters

Abstract

Ammonia-oxidizing archaea (AOA) are promising candidates for replacing ammonia-oxidizing bacteria in wastewater treatment. However, limited efforts have been made to enrich copiotrophic-AOA in situ competitively. To this end, two laboratory-scale intermittent aerated biofilters (upflow-aerated biofilter (R1) and downflow-aerated biofilter (R2)) were comparatively employed for the treatment of mainstream wastewater. An extended non-aerobic cycling strategy led to higher residual ammonia-nitrogen levels (0.01–18.7 mg/L), denser biofilms, and facilitated the dominance of Nitrosocosmicus-like AOA (R1: 70.31 %; R2: 82.32 %). Additionally, the AOA in both biofilters were the main contributors (62 %–66 %) to the highly efficient nitrification process. Compared with R1, R2 had a higher abundance of Nitrosomonas and Nitrospira, a lower ammonia oxidation rate, and a simpler co-occurrence network of nitrifiers. The protein content induced by intermittent aeration significantly affected the AOA community. Candidatus Brocadia (3.62 %–7.82 %) was also auto-enriched in both biofilters. Therefore, in situ enrichment of Nitrosocosmicus-dominant nitrifying microorganisms is conducive to developing an environment-friendly, energy-efficient, high ammonia-nitrogen removal AOA-based partial nitrification-anammox process.