I’m a medical student at Karolinska Institute in Sweden currently involved in a project about prevention of Legionnaires’ disease, and I have found your website to be a valuable resource.
I’m writing about the use of free radicals in the elimination of Legionella in water systems. Is this something you are planning on evaluating? The technique is very interesting and has been proven very efficient on the elimination of Legionella species – among others – in water systems.
We are assuming you are speaking of the free radicals of oxygen obtained by disinfecting with ozone or hydrogen peroxide. We have not investigated hydrogen peroxide in our laboratory.
The Yamagiwa et al article presents a view of hydrogen peroxide (Yamagiwa K, et al. (2001) Disinfection Kinetics of Legionlla pneumophila by Hydrogen Peroxide. Journal of Chemical Engineering of Japan. 34(8),1074-1077). Hydrogen peroxide is slightly more stable than ozone, but maintenance of a sufficient residual in large drinking water systems may still be difficult. Additionally, we are not sure in the U.S. if hydrogen peroxide could be legally used as a drinking water disinfectant. If hydrogen peroxide is effective it may be most useful in applications such as spas and whirlpools.
There have been numerous other studies of ozone which compares the recommended concentration with other oxidizing biocides. Ozone was effective in our model plumbing system ( Muraca Appl Environ Microbiol 1987). One note on ozone, it is very reactive and as such does not produce a residual to carry disinfection effects into a distribution system. This can be a problem for piping systems which have an established biofilm harboring Legionella far from the point of ozone application.