AWWA JAW63842

A number of mathematical models have been developed over the past century to represent the dose-response curve of a microbial population exposed to a disinfectant. Beginning with the Chick-Watson model and continuing through the Gard, Hom, and delayed Chick-Watson models, these representations have in common their foundation on the concept that the interaction between a microorganism and a disinfectant is a kinetic process similar to that between chemicals undergoing a reaction. The author reviews the development of these models and proposes an alternative interpretation based on the diversity of the microbial population in its resistance to a disinfectant. If additional research confirms its validity, this hypothesis should help explain the variability seen in microorganisms' responses to a specific disinfectant. A better understanding of how microorganisms are inactivated will assist utilities in complying with regulatory requirements and may lead to improved engineering designs for meeting those requirements. Includes 23 references, table, figures.