Calibration and validation of an ASM3-based steady-state model for activated sludge systems—part I: : prediction of nitrogen removal and sludge production

The steady-state model from Siegrist and Gujer (1994) which can be used for the design and optimisation of nitrogen-removing activated sludge plants is applied to the stoichiometrics and kinetics of a validated Activated Sludge Model No. 3. It considers the wastewater composition, the effect of the electron acceptor on the average sludge production, the oxygen input into anoxic volumes, denitrification in the secondary clarifier, the temperature and various operating conditions. The organic substrate for denitrification originates from readily degradable substrate from the influent, from the hydrolysis of slowly degradable particulate substrate along the activated sludge plant and from the endogenous respiration of the biomass. The model is calibrated and validated with data from long-term full-scale and pilot-plant experiments for Swiss municipal wastewater. The most sensitive parameters as well as the uncertainty of the model prognosis for various COD-to-nitrogen ratios from inlet water and anoxic volume fractions were calculated with the aid of sensitivity analyses and Monte-Carlo simulations. Excel spreadsheets of the model for different flow schemes are available from the corresponding author.