An earlier study on theoretical identifiability of parameters for a two-step nitrification model
showed that a unique estimation of the yield YA1 is possible with combined respirometric-titrimetric data,
contrary to the case where only one type of measurement is available. Here, the practical identifiability of
model parameters was investigated via evaluation of the output sensitivity functions and the corresponding
Fisher Information Matrix (FIM). It appeared that the FIM was not sufficiently powerful to predict the practical
identifiability of this case with combined measurements as parameters could indeed be identified despite the
fact that the FIM became singular. The accuracy of parameter estimates based on respirometric and
titrimetric data and combination thereof was also investigated. Estimation on titrimetric data (Hp) was very
accurate and a fast convergence of the objective function towards a minimum was obtained. The latter also
holds for estimation on oxygen uptake rate data (rO), however with a lower accuracy. Parameter estimation
based on oxygen concentration data (SO) was more complex but resulted in a higher accuracy. Thus, when
the highest accuracy is needed it is recommended to estimate parameters initially on Hp and/or rO data, and
to subsequently use these parameters as initial values for final, and more accurate estimation on SO data.



Auteur: Petersen B., Gernaey K. & Vanrolleghem P.A.
Herkomst: Water Science and Technology. Vol. 43(Nr. 7), pp. 347-356. [PVR266] Copyright IWA & the authors
Referentie: Referentie