The power input to the aerated system (Pg) and the superficial gas velocity (vs) were calculated using the equations presented in the Section 2, converting the specific air flow rate to real volumetric gas flow rate (Fg). According to Michel and Miller [46], the parameters of these empirical equations depend of system geometry and are only valid for superficial gas velocity between 0.042 m s−1 and 0.180 m s−1 and stirring speed between 180 rpm and 960 rpm, that cover the conditions used in this work.