This paper presents the methods and results of Monod kinetic constant determination for heterotrophic bacterial growth in an aerated submerged fixed-bed biofilm reactor (ASFBBR) treating petrochemical wastewater. The methods originally developed for activated sludge are successfully adapted to biofilm kinetics characterization. The results are discussed and compared with the values given by other authors. The purpose of this calibration is to develop a mathematical model for a novel approach toward biofilm system dimensioning.