**3.3 Mathematical and kinetic models**

The application of mathematical models to biofilm reactors suffers due to lack of availability accurate kinetic models and uncertainty in model parameters. Therefore, appropriate selection of kinetic model and accurate determination of its parameters is required for successful modeling of biofilm reactors. The biological reaction rates are generally represented by Monod kinetics and also occasionally by Contois and Haldane models. In the past, efforts have been made to determine the parameters of kinetic models of biofilm reactors, mostly experimentally [29–31]. Various researchers [32–35] have reported that numerical evaluation of kinetic parameters is an attractive alternative to the experimental methods for biofilm processes. By numerical approach, the parameters of the kinetic models of biofilm processes are determined as a consequence of the validation of their mathematical models with the aid of measured data. The approach of determining the model parameters such that the behavior of the process model approximates the observed process behavior is known as inverse modeling.
