This study describes a technique for estimating biokinetic and mass transfer parameters for biofilm processes in wastewater treatment. The reactor used consisted of a column divided into separate units packed with expanded clay pellets. Samples were taken at the exit of each unit. Oxygen mass transfer and oxygen consumption rate were determined. The system was operated with cocurrent upflows of air and industrial wastewater. A mathematical approach was developed to estimate biokinetic parameters such as the maximal oxygen removal rate, saturation constant and internal diffusion coefficient.