A New Approach to Modelling Substrate Inhibition

Abstract

Substrate inhibition, which is one of the most frequently observed phenomena in the biological treatment of industrial wastewaters, has been the subject of numerous studies. Yet there are still cases which cannot be adequately described by the existing models. In this paper, a review of substrate inhibition approaches was made. A new model is proposed that assumes a common mechanism for substrate and product inhibition. The model is a continuous function having a maximum growth rate at the critical substrate concentration, beyond which the growth rate decreases as the substrate concentration is increased. The model also predicts the maximum substrate concentration where the growth ceases. The model was tested using existing data in the literature to assess the model response and predictability of critical points. The literature data have been selected from the studies conducted on pure and mixed cultures in batch and continuous reactors for phenol and several phenolics as well as from the studies which employed the Haldane model. A curve fitting method was used to determine the model parameters. The fit of the model to the data was satisfactory, particularly for the substrate concentrations exceeding maximum growth rate.