A general model of the activated sludge reactor with dispersive flow—II. model verification and application

A general dynamic model of the activated sludge reactor, including biological processes, hydraulics, oxygen transfer and temperature, was verified against both steady-state and dynamic field data. These data originated from the Rock Creek wastewater treatment plant located in Hillsboro, Oregon (USA). During simulations only one set of the model parameters was used. The model was capable of predicting dissolved oxygen concentrations and consumption, ammonia concentrations, and nitrate+nitrite concentrations with time and distance along the activated sludge reactor. Uncertainty analysis enabled the classification of model parameters (kinetic and stoichiometric coefficients, and wastewater components) according to model sensitivity. The maximum growth rate of nitrifiers, μA,max, and the ammonia concentration, SNH, were the most sensitive coefficient and wastewater component, respectively, when the sum of ammonia, nitrate+nitrite, dissolved oxygen concentrations and total oxygen uptake rate was taken into account. Application of the model was demonstrated by analyzing the impact of changing the operational mode (from A/O process to 4-stage Bardenpho) on dissolved oxygen conditions and nitrogen removal.