To explore the metabolic versatility of "Candidatus Brocadia sinica" in the presence of VFAs, the impacts of VFAs on anammox activity and nitrogen removal were investigated in this study. Results found that low VFAs concentrations has no affect on anammox activity and the removal efficiencies of NH4+-N and NO2-N. However, "Ca. Brocadia sinica" showed higher adaptability to some VFAs stresses. Furthermore, Illumina MiSeq pyrosequencing results indicated that the microbial community structures varied significantly and the phyla Chloroflexi, Proteobacteria, Bacteroidetes and Chlorobi were dominated. Finally, qPCR was performed to validate the growth of anammox bacteria and gain the quantitative insights into the correlation between nitrogen transformation rates and the key functional genes in the organotrophic anammox system. Combined analysis clearly demonstrated that the coupling of the anammox, denitrification and DNRA were the noteworthy pathway for the simultaneous removal of nitrogen and organic carbon. (C) 2015 Elsevier Ltd. All rights reserved.