Identification and quantification of anammox bacteria in eight nitrogen removal reactors

Various studies have revealed anaerobic ammonium oxidation (anammox) as a very attractive alternative process suitable for nitrogen removal from wastewater. Here we investigated anammox bacteria in eight different nitrogen removal reactors. The diversity and abundance of anammox bacteria were determined by the 16S rRNA gene analysis, fluorescence in situ hybridization with specific probes and real-time quantitative PCR (qPCR). In these reactors, at least eight unique near full length anammox 16S rRNA gene sequences were detected, which were distributed over two genera; Candidati Brocadia and Kuenenia. FISH results confirmed that only one anammox bacterium dominated the community in each of the eight reactors investigated in this study. qPCR analysis revealed that anammox bacteria were present in seven of the reactors in the order of 10(9) cells/ml and 10(7) cells/ml in reactor A1. The dominant and divergent Brocadia-like anammox phylotype in one reactor represented a novel species for which we propose the name Candidatus Brocadia sinica. Taken together, these results indicated that a single seeding source could be used to seed anammox reactors designed to treat different types of wastewater, which could lead to a faster start-up of bioreactors.