Hi Gloria, All the ...

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Hi Gloria,

All the techniques based on O3, Cl2, ClO2, Chloramine, and UV have a high bactericidal effect (Ability to reduce germs) however for the resudual effect, ie, a residuel effect after disinfection Is only for chlorine and its derivatives. From Dégrement, 1989 we have:

                                               O3        Cl2         ClO2        Chloramine       UV

Bactericidal Effect             +++        ++             ++                       +             ++

Residuel Effect                      0           +              +                        ++            0

So a need of the residual effect is there for any reuse  of the disinfected water, transport of water etc. 

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Chloramines aren't used  in Switzerland an Germany as additive for drinking water and in England rather seldom*. In Switzerland, they are seen as byproduct of amine/ammonium contamination and chlorination, and they aren't welcome at all. Chloramines aren’t listed on the positive list for allowed drinking water additives / treatments in Switzerland.

Quelle: https://www.admin.ch/opc/de/official-compilation/2017/1023.pdf, Verordnung des EDI über Trinkwasser sowie Wasser in öffentlich zugänglichen Bädern und Duschanlagen (TBDV) vom 16. Dezember 2016, abgerufen am 28.07.2016)

 

Also in Germany the chlorination as prevention tool is not allowed anymore, chlorination with it is only permitted as emergency tool in case of contamination.

“Eine vorbeugende Desinfektion des Trinkwassers, die sogenannte „Schutz-Chlorung“ ist in Deutschland seit der Novellierung der Trinkwasserverordnung vom 1. Januar 1991 nicht mehr zulässig.”Quelle: https://de.wikipedia.org/wiki/Chlorung, abgerufen am 28.07.2016

When you are using UV-C, in Switzerland the "state of the art" is to control the turbidity, which shall be below 0.2 FNU ==NTU (Formazin-NephrelometicUnits==Nephelometric Turbidity Unit). If the waters turbidity is above that, the water must be rejected or filtered. Additionally, the UV-C machine checks inherently the transmission together with the lamp power, so if the water would have much UV-C absorption, the sensor wouldn't get enough UV-C light and therefore the machine would go into "Alert-state". But I never seen that in real life, it is more common, that the lamp goes "dark" because of is use after several thousand working hours, or after very long still stand, a biofilm build-up on the quartz-tubes and sensor window can provoke the same result.  

Seldom low chlorination levels(equal or lower 0.1 mg/l) may be used in Switzerland for protection of regrowth of germs in the drinking water net, especially in summer, but rather the net is planned to have a constant flow so that the water stays cool in all the tubes. That is why it doesn’t make sense to shut down all the public fountains for energy or water saving purposes…

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Thanks very much for your answer and all the information attached. Very useful and interesting.

Regards,

Gloria

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