RESPIROMETRIC ASSAY FOR BIOFILM KINETICS ESTIMATION - PARAMETER IDENTIFIABILITY AND RETRIEVABILITY

Currently, no fast and accurate methods exist for measuring extant bio kinetic parameters for biofilm systems. This article presents a new ap proach to measure extant biokinetic parameters of biofilms and examine s the numerical feasibility of such a method. A completely mixed attac hed growth bioreactor is subjected to a pulse of substrate, and oxygen consumption is monitored by on-line measurement of dissolved oxygen c oncentration in the bulk liquid. The oxygen concentration profile is t hen fit with a mechanistic mathematical model for the biofilm to estim ate biokinetic parameters. In this study a transient biofilm model is developed and solved to generate dissolved oxygen profiles in the bulk liquid. Sensitivity analysis of the model reveals that the dissolved oxygen profiles are sufficiently sensitive to the biokinetic parameter s-the maximum specific growth rate coefficient (<(mu)over cap>) and th e half-saturation coefficient (K-s)-to support parameter estimation if accurate estimates of other model parameters can be obtained. Monte C arlo simulations are conducted with the model to add typical measureme nt error to the generated dissolved oxygen profiles. Even with measure ment error in the dissolved oxygen profile, a pair of biokinetic param eters is always retrievable. The geometric mean of the parameter estim ates from the Monte Carlo simulations prove to be an accurate estimato r for the true biokinetic values. Higher precision is obtained for <(m u)over cap> estimates than for K-s estimates. In summary, this theoret ical analysis reveals that an on-line respirometric assay holds promis e for measuring extant biofilm kinetic parameters. (C) 1998 John Wiley & Sons, Inc.