Modeling the effect of initial concentration of Escherichia coli suspensions on their inactivation by chlorine

Abstract

The objective of this investigation was to model the influence of the initial microbial concentration on the Escherichia coli resistance to chlorine. A suspension test was used to evaluate the antibacterial efficacy of chlorine. Chlorine doses ranged from 0.6 to 0.9 mL/L, from 0.3 to 0.7 mL/L, from 0.15 to 0.3 mL/L and from 0.1 to 0.2 mL/L when the initial microbial concentration was 1.2 × 108, 6 × 107, 6 × 105 and 6 × 105 CFU/mL, respectively. In order to describe the survival curves of E. coli, a mathematical model based on a biphasic inactivation was used. Initial microbial concentration had a significant influence on the kinetics of inactivation and on the resistance of E. coli to chlorine. In order to obtain a good repeatability and reproducibility of the bacterial suspension test, the initial concentration of bacterial suspensions should be evaluated and standardized. © Copyright 2005, Blackwell Publishing.