The paper presents the study of treatment of wastewaters resulted from a petrochemical platform. The purpose of this work was to simulate the industrial process under the Monod model and to determine if the model could be used for engineering working. The Monod model used to simulate the industrial process was based on equation Monod modified by Jarzebski et al. First, the biodegradation time was determined using the model at an initial phenols concentration of 23.4 mg/L and a pure culture of Pseudomonas putida for the phenols biodegradation. Then, the biodegradation time was determined in the same operating conditions, but using a mixed culture of bacteria, Pseudomonas (various species). In both cases the results were compared with the experimental time. The model provided good results compared to the industrial process when selecting a pure culture of Pseudomonas putida for phenols biodegradation.