Modeling the nitrogen dynamics in an alternating activated sludge process

The paper presents a relatively simple model describing the nitrogen dynamics in an alternating waste water treatment process. Only two components, ammonia and nitrate plus nitrite, are considered, and reaction rates are described using empirical expressions. Despite its simplicity, the model serves well for two distinct purposes: as a prediction model for use in control strategies and as a steady state (limit cycle) model for process analysis. Nitrification rate limitation at low ammonia concentrations is shown to influence model predictions significantly. A correction factor is proposed, which allows the less computationally intensive case of zero order kinetics to be employed when limitation occurs.