Kinetics of Escherichia coli inactivation with ozone

The kinetics of Escherichia coli inactivation with ozone were investigated with semi-batch and continuous-flow tubular reactors in solutions buffered with phosphate at pH 6 and 8, temperatures ranging from 5 to 25 °C, and in the presence (0.01 M) and absence of radical scavenger tert-butanol. Ozone concentrations and contact times investigated ranged from 6 to 41 μg/l, and 1.8-33 s, respectively. In activation kinetics were found to be first-order with respect to both ozone concentration and active microorganism density. The overall second-order rate constant was 130 l/(mg s) at 20 °C, and the corresponding activation energy was 37,100 J/mol. Experimental results corresponding to tests performed at pH 6 and 8, and in the presence (0.01 M) and absence of radical scavenger tert-butanol, confirmed that dissolved molecular ozone was primarily responsible for E. coli inactivation in the range of experimental conditions investigated.