A model of the simultaneous nitrogen and carbon removal in a biofilm

A model predicting the turnover of ammonium-nitrogen, nitrate-nitrogen and carbonaceous compounds in a biofilm reactor using the ion exchanger clinoptilolite as support material is presented. The process described by the model is the oxidation of ammonium-nitrogen and reduction of the resulting nitrate to free nitrogen gas. The fate of carbonaceous material in the process is oxidation to carbon dioxide, but the model predicts accurately that the dissolved oxygen concentration and the load criteria are essential in determining the mode of oxidation. The model takes into account the fact that the yield of bacteria will vary according to the environmental conditions, and that bacteria in a biofilm are subject to the same ecological considerations that apply elsewhere in ecosystems.