Ozonation
Ozone is a gas,O3
, which is a powerful oxidising agent. Major advantages are apparent in
coloured waters as it can reduce odours, tastes and colour. However, ozone manufacture
takes place on site causing handling problems and increased expense. Other problems
associated with ozonation include precipitation of iron and manganese, and it is unsuitable
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at higher turbidities. Doses between one and two mg l-1 with a contact time of 15 minutes
are usually sufficient. The ozone disappears fairly rapidly from the water following
treatment. This means that no stable residual enters the distribution network so that some
problems with re-infection in the mains could be experienced. Ozone is used commonly in
France and adopted in the UK as an oxidant preceding GAC adsorption for the removal of
pesticides.