Modelling biological phosphorus and nitrogen removal in a full scale activated sludge process

A previously derived metabolically structured model for the biological aerobic and anoxic phosphorus removal was combined with the ASM no. 1 and tested in its capacity to describe a full scale biological nitrogen and phosphorus removal WWTP. The sensitivity of the effluent concentrations and the sludge production towards the stoichiometric and kinetic coefficients, the influent composition, the set-up of the hydraulic model and the flows of air, mixed liquor and return sludge was analysed. This showed that besides a limited number of model parameters (12%) the influent characterisation influenced the model output significant. For calibration of the model only 3 out of the 60 default parameters together with the unknown air input needed to be changed approximately 40% to describe the measurements of soluble components at different places in the full scale WWTP as a function of time. The choice of parameters to calibrate was done on the basis of process and model knowledge rather then on the sensitivity analysis. For the calibration the in-process measurements were much more informative then the effluent measurements.