Structure and composition of biofilm communities in a moving bed biofilm reactor for nitritation-anammox at low temperatures

It is a challenge to apply anaerobic ammonium oxidation (anammox) for nitrogen removal from waste-water at low temperatures. Maintenance of anammox- and aerobic ammonia oxidizing bacteria (AOB) and suppression of nitrite oxidizing bacteria (NOB) are key issues. In this work, a nitritation-anammox moving bed biofilm pilot reactor was operated at 19-10 degrees C for 300 d. Nitrogen removal was decreasing, but stable, at 19-13 degrees C. At 10 degrees C removal became unstable. Quantitative PCR, fluorescence in situ hybridization and gene sequencing showed that no major microbial community changes were observed with decreased temperature. Anammox bacteria dominated the biofilm (0.9-1.2 x 10(14) 16S rRNA copies m (2)). Most anammox bacteria were similar to Brocadia sp. 40, but another smaller Brocadia population was present near the biofilm-water interface, where also the AOB community (Nitrosomonas) was concentrated in thin layers (1.8-5.3 10(12) amoA copies m (2)). NOB (Nitrobacter, Nitrospira) were always present at low concentrations (<1.3 x 10(11) 16S rRNA copies m (2)). (C) 2013 Elsevier Ltd. All rights reserved.