Fig. 3.

Evolution of the concentrations of nitrogen species (NH₄⁺, NO₂⁻, NO₃⁻) and dissolved organic matter (COD_sol) during representative SBR cycles at 15 °C (dotted area: initial settling + feeding phase; white areas: pre- and post-anoxic phases; grey area: aeration phase at 0.18 ${\mathrm{mg}}_{{\mathrm{O}}_2}·{\mathrm{L}}^{-1}$) (a). Nitrogen species, COD_sol and DO set-point during in situ batch tests conducted by spiking acetate as a representative readily biodegradable organic compound under different DO conditions (set at 1.5, 0.2 and 0 ${\mathrm{mg}}_{{\mathrm{O}}_2}·{\mathrm{L}}^{-1}$), at 15 °C and in absence of ammonium (b).