Ozone reacts with natural organics to increase their biodegradability, measured as assimilable organic carbon. To avoid undesirable bacterial growth in distribution, ozonation is normally used with subsequent treatment, such as biological filtration or granular activated carbon (GAC), to remove biodegradable organics, followed by a chlorine residual, as ozone does not provide a disinfectant residual. Ozone is effective for the degradation of a wide range of pesticides and other organic chemicals.
==Suitable conditions==
Ozone is currently the next most widely used drinking water disinfectant after chlorine (there are some 1100 water treatment plants
using ozone worldwide), although its use is almost exclusively limited to the industrial countries with high-integrity piped water networks.
Ozone does not provide residual protection against recontamination in the distribution system. Therefore, its common use is to pre-treat the water source before chlorination in a municipal system, so that a smaller chlorine dose is required.
Although ozonation can effectively disinfect water, it is not suited for most developing country applications owing to its high cost, need for operational and maintenance infrastructure, and lack of residual protection in the distribution system.
==Construction, operations and maintenance==
Care is needed in operating and maintaining the generators, and in destroying excess ozone so it is not released into ambient air.
==Acknowledgements==
* [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CGcQFjAB&url=http%3A%2F%2Fwhqlibdoc.who.int%2Fpublications%2F2011%2F9789241548151_eng.pdf&ei=0Za6T7rBFMKZiQLZhOH1Bg&usg=AFQjCNGx2Q3Rc5yFmbygAIgmJOjg5CSp7g&sig2=8YRhyKpjfeGy8xqp9j8X4Q Guidelines for Drinking-water Quality.] Fourth edition. WHO, 2011.
* Gadgil, Ashok. [http://www.annualreviews.org/doi/abs/10.1146/annurev.energy.23.1.253?journalCode=energy.2 DRINKING WATER IN DEVELOPING COUNTRIES.] 1998.