hello Valentin,

if you understand (or google translate) portuguese this should help a bit :)

http://www.airliquide.pt/pt/as-suas-necessidades-sao/tratamento-de-aguas/gases-para-tratamento-de-aguas/ozono-o3.html#.VTuC0lJFBdg

Hi Valentin, 

I hope this may help you :-)

Regards, Valerio

http://www.airliquide.it/it/le-applicazioni-dei-gas/trattamento-acque/trattamento-acque-con-ozono.html

http://www.lenntech.it/biblioteca/ozono/potabile/ozono-applicazione-acqua-potabile.htm

http://www.xylemwatersolutions.com/scs/italy/it-it/products/catalogo-prodotti-xylem/Trattamento%20con%20Ozono/Pagine/default.aspx

http://www.xylemwatersolutions.com/scs/italy/it-it/Angolo%20del%20tecnico/Manuali/Documents/1_UV_Ozono.pdf

http://www.aslan.it/applicazioni-ozono/trattamento-acque/potabilizzazione-delle-acque/

http://diatomic-water.org/

http://www.ozonoapplicazioni.it/

http://www.lenntech.it/biblioteca/ozono/faq/faq-ozono.htm

In Denmark the water supply is based on groundwater and we do not need disinfection. Therefore I am reasonable sure we do not have any ozone disinfection in municipal water supply.

In almost all water treatment plant in India Ozone is not used in Municipal water supply for disinfection In India as my knowledge is concerned

In Belarus water treatment plants mostly use different types of hypochlorites for water disinfection. Using of ozone as disinfectant is under investigation in our country now.

Many US plants use ozone for drinking water and wastewater.  See paper below from the IOA for a review on these plants.

http://www.tandfonline.com/doi/abs/10.1080/01919519008552212?journalCode=bose20

Ozone applications Drinking water. Because of its excellent disinfection and oxidation qualities, ozone is widely used for drinking water treatment. Ozone can be added at several points throughout the treatment system, such as during pre-oxidation, intermediate oxidation or final disinfection.