The effect of ozone onLegionella pneumophila and other bacterial populations in cooling towers

Ozone was found to reduce the numbers of bacteria detectable by plate counts and the numbers of presumptiveLegionella pneumophila (DFA-reactive cells), including those that were INT positive, in test cooling towers. The numbers of DFA-reactiveL. pneumophila eventually reached those of the makeup water (Troy, NY, city water). Microbial slime on the interior tower surfaces andPseudomonas populations in the tower waters were also reduced. Water chemistry parameters measured showed no tendency toward a condition that would cause accelerated deterioration of tower material.