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Health and sanitation
Rapid and effective
inactivation of legionella
with ozone
By Environmental Protection Agency, document EPA 810-R-16-001
Ozone is used in drinking water treatment for disinfection and oxidation.
Ozone is generated on site as a gas using either air or
liquid oxygen and is then transferred (dissolved) into the
water phase. When dissolved in water, molecular ozone
(O 3 ) is unstable and decomposes to hydroxyl radical,
which is a stronger and typically more reactive oxidizing
agent than molecular ozone.
Ozone decomposes quickly during water treatment (USEPA,
1999d, 2007). Therefore, during a typical ozonation
process, both molecular ozone and the hydroxyl radical
may contribute to the oxidation of contaminants of concern.
The relative importance of these two oxidants depends on
the concentrations of the oxidants and the reactivity of the
contaminant with each oxidant.
The use of ozone in drinking water treatment is widespread
throughout the world. As an oxidant, ozone can be used to
oxidize iron, manganese, taste and odour compounds, and
DBP precursors. It can oxidize organic matter into smaller
molecules that are more easily biodegradable.
As a primary disinfectant, ozone is more effective than
chlorine, chloramines and chlorine dioxide for inactivation of
cryptosporidium, Giardia and viruses (USEPA, 1999d, 2007).
However, ozone cannot be used as a secondary disinfectant
because it decays very rapidly and cannot maintain a residual
in the distribution system (USEPA, 1999d, 2007).
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Characterisation of effectivene