Fig. 1.

Temporal evolution of the volumetric anammox activity and the relative abundances of anammox populations in the sludge during the three successive experimental phases at 29 °C, for reactors R1 (panel (a), (b)) and R2 (panel (c), (d)). (a, c) Anammox activity expressed as the sum of NH₄⁺ and NO₂⁻ consumption. (b, d) Relative abundance of the guilds of known anammox populations (AMX; Cy3-labeled Amx820 and Bfu613 oligonucleotide probes) and aerobic ammonia oxidizing bacteria (AOB; FLUOS-labeled AOB-mix) measured by 16S rRNA-targeted FISH over the total bacterial population (EUB; Cy5-labeled EUB-mix), as well as concentrations of total suspended solids (TSS) and TSS together with wall-biofilms (TSS + biofilm) as estimated at the end of the experiment. The error bars represent the standard deviation of the FISH quantification. In Phase I, the reactor was operated for full nitritation and anammox on municipal wastewater pre-treated for COD removal (MWW_pre-treated). In Phases II and III, the reactor was operated for anammox only with synthetic MWW (MWW_synthetic) and MWW_pre-treated amended with NH₄⁺ and NO₂⁻, respectively. The vertical arrows indicate the day on which effluent biomass began to be regularly reintroduced to the reactor.