Advances in disinfection testing and modelling

Aims: To develop a set of kinetic equations which more ably describe the di sinfection process. Methods and Results: A group of functions, the fa(t) equations, based on th e model used for the quantification of microbial inhibition, was produced. These functions introduce a limit to the numbers of micro-organisms capable of being disinfected. These new expressions were shown to be more general forms of currently-used (e.g. log-linear) disinfection models, and accommod ate the lags and/or tails of non-linear log-survivor-time plots. An advance in the experimental procedures used to obtain disinfection data, using an optical density technique, was developed concomitantly. Conclusions: The methods of analyses (experimental and modelling) allow the researcher to examine, more ably, five-minute disinfection (or specific ti me disinfection tests) as well as the more important disinfection rate anal yses. Significance and Impact of the Study: The fa(t) equations are an improvemen t over commonly-used rate models of disinfection, which are shown to be spe cial cases of these equations. This raises the question as to whether our c urrent understanding of the kinetic basis of disinfection requires revision .