Fig. 2

Dynamics of pH, alkalinity, ammonium–nitrogen and volatile fatty acids contents in the sludge for each reactor over time. Progress over time for CR, R1, R2, and R3, respectively, of pH—a, d, g, j; total alkalinity (Alk., mg CaCO₃ L⁻¹ of sludge) and ammonium–nitrogen content (NH₄–H, kg NH₄–N m⁻³ of sludge)—b, e, h, k; volatile fatty acid content (VFA, mg kg⁻¹)—c, f, i, l; CR is the cautiously fed reactor; R1, R2 and R3 are the reactors exposed to increasing organic loading rate; P0–P5 are the sampling periods chosen for microbial community analyses