A new mathematical approach has been developed to describe the processes occurring in the electrochemical treatment of wastewater polluted with organic materials, and it is applied to cells that incorporate active electrodes. The reactivity of these electrodes causes difficulties in the elaboration of the model, because the electrogenerated species and the processes in which they are involved must be included in the model. A number of adjustable parameters corresponding to the rates of the chemical process are included in the model. The model is applied to the electrochemical treatment of wastes containing only inorganic salts as well as to systems containing several organic compounds, such as carboxylic acids (formic, oxalic, and maleic) or phenol, on stainless steel (SS) electrodes (as an example of typical active behavior). The good agreement obtained between model and experimental results provides evidence for the reliability of the model and validates the simplifications assumed to explain the behavior of the active anodes.