Sensitivity analysis of autotrophic N removal by a granule based bioreactor: Influence of mass transfer versus microbial kinetics

► Mass transfer and microbial kinetics mechanisms were studied systematically. ► Highest removal efficiency was obtained at an oxygen/TAN loading ratio of 1.9 gO2/gN. ► Below this value N removal was impacted 75% by AOB kinetics and 10% by mass transfer. ► Above this value the activity of AnAOB is inhibited by oxygen and NOB are present. ► Mass transfer had similar impact on different granules sizes in the range of 0.5-2 mm.