Abstract
Legionnaires’ disease remains a serious health problem globally, caused
by the Gram-negative bacteria Legionella. The study objective was to
characterize the ability of ozone to kill viable but non-culturable
(VBNC) Legionella and examine the kinetic characteristics of VBNC
Legionella inactivation. The removal of the living Legionella by ozone
was highest (>99%) among VBNC, living (culturable, no
including VBNC), and dead Legionella trials. Ozone can kill VBNC
Legionella at a more rapid rate than the other Legionella states. Ozone
can fragment Legionella into small DNA fragments and can damage the
Legionella cell membranes and DNA. Based on our results, the killing
process was characterized as follows. Ozone oxidizes living Legionella
to VBNC Legionella and then oxidizes VBNC Legionella to dead Legionella.
Ozone damages the dead Legionella cell membrane and enters the dead
Legionella body. Ozone decomposes dead Legionella DNA into small DNA
fragments. The VBNC Legionella inactivation kinetic process in the
wastewater was expressed mathematically. These equations can be used
widely for predicting variations of VBNC Legionella concentrations and
thus as a framework for controlling the activity of the bacteria and,
ultimately, Legionnaires’ disease.