Ozone is a powerful oxidising agent which, when dissolved in water, produces a broad spectrum biocide that destroys all bacteria, viruses and cysts. Ozone remains effective over a wide pH range from ph 6.5 to above pH 9.5.
Ozone owes its biocidal effectiveness to its ability to oxidise organic materials in bacterial membranes, which weakens the cell wall leading to rupture and immediate death of the cell. In contrast, chlorine, and all other oxidising and non-oxidising biocides, must be transported across the cell membrane in order to interfere with either the nuclear reproductive mechanism or various enzymatic life giving reactions in the cell, in either event resulting in substantially less biocidal efficiency.
For this reason, ozone is capable of destroying all bacteria, algae and biofilms with no risk of resistance build up or immunity. Even resistant and problematic aqueous micro organisms, such as Giardia, Cryptosporidium, streptococcus fecalis and E.coli causing grave human health concerns in potable water, are readily and rapidly inactivated by ozone.
Although viruses are more resistant to ozone destruction than bacteria is, viral inactivation occurs more readily with ozonation than with chlorination. Poliovirus types I, II and III are 99% inactivated by exposure to 0.3 mg/ltr, maintained over a 3 minute period.
Concentrations of 0.4 to 0.5 mg/ltr ozone in bulk liquid have been shown to produce a 100% kill of Pseudomonas bacteria, normally responsible for biofilms, in 2 to 3 minutes. Removal of biofilms could be achieved by using ozone at concentrations of 0.08 to 0.33 for two to six hours (KAUR et al – University of Birmingham).
A greater than 99% kill of Legionella Serogroup 1 was achieved in 5 minutes using a concentration of 0.1 to 0.3 mg/ltr ozone (RL Tyndall et al & GW Brundrett 1992).