Ozone oxidizes the transition metals to their higher oxidation state in
which they usually form less soluble oxides that are then easy to
separate by filtration. Iron, for example, is usually in the ferrous
state when dissolved in water. With Ozone it yields ferric iron which
is further oxidized in water to Ferric Hydroxide ? a molecule that is
very insoluble and precipitates out.
Other metals such as Arsenic (in the presence of Iron),
Cadmium, Chromium, Cobalt, Copper, Lead, Manganese, Nickel, and Zinc
can be treated in a similar way. At Ozone levels above 4 ppm however,
Manganese will form soluble permanganate, showing up as a pink color.