A TECHNIQUE FOR OBTAINING REPRESENTATIVE BIOKINETIC PARAMETER VALUES FROM REPLICATE SETS OF PARAMETER ESTIMATES

The rational design and simulation of biotreatment systems requires so und mathematical models and reliable parameter estimates. Biodegradati on kinetics are usually modelled using the Monod or Andrews equation, and model parameters are usually obtained by fitting an observed conce ntration-time profile to the model. Since the nature of the models and the method of parameter estimation result in correlation between the parameters, the question arose as to how to obtain a single set of Par ameters Representing the Average mu-S response (referred to as PRAMUS values) from replicate sets of experimentally derived parameter estima tes. The common approach of using the arithmetic mean parameter values was adequate only for data conforming to the Monod model, particularl y when the variability among replicate parameter estimates was small. For the Andrews model, nonlinear regression was used to obtain PRAMUS values, The ability of the PRAMUS and mean parameter values to reprodu ce the average mu-S response and to simulate experimentally observed o xygen uptake was evaluated. On this basis, the use of PRAMUS values is recommended, particularly when dealing with systems modelled by the A ndrews equation, with experimental data characterized by a high degree of experimental variability, and/or with process situations where hig h substrate concentrations are likely to be encountered, e.g. shock lo ads. (C) 1998 Elsevier Science Ltd. All rights reserved.