This book covers a fruitful literature review of the anaerobic process. It includes a description of the different kinds of anaerobic reactors, emphasizing on UASB reactor. It takes into account the granules development, the kinetics models, and a review of the existing models describing the UASB reactor behavior. The main purpose of this work is the development of a model able to predict the substrate degradation, the biomass growth, and the location of the granule size along the height of the reactor. Based on knowledge about transport phenomena, a model was developed in order to describe...