Biofilm phenotypes and internal community succession determines distinct growth of anammox bacteria in functional anammox biofilms

In this study, time-series anammox functional biofilms were obtained in a lab-scale simultaneous partial nitritation/anammox process for treating high-strength ammonium. The variations in the biofilm phenotypes, community succession, and anammox bacteria abundance over time were evaluated using optical microscopy, 16S rRNA gene sequencing, and qPCR. The result revealed that biofilm has three distinct stages of the community development trajectory across a 182-day temporal scale. Anammox bacteria growth rates were 0.035 d-1, 0.0015 d-1, and 0.011 d-1, respectively. The diversity and network analysis suggested that the positive priority effect of ammonia oxidizing bacteria was the primary factor for the rapid proliferation of anammox bacteria, and the species replacement triggering priority effect forfeiture and substituted functional recruitment were reasons for the slow proliferation and stable proliferation of anammox bacteria, respectively. Taken together, the higher microbial diversity and stable community composite were key prerequisites for the proliferation of the anammox bacteria.