UV Disinfection in Drinking Water Supply

UV disinfection is the only physical disinfection process approved in Germany for public water treatment. No additional treatment substances are added to the drinking water. Currently approved are UV low-pressure lamps and UV medium-pressure lamps with a disinfection efficacy of at least 400 Joule/m² (referred to 254 nm). 

This website provides an overview of the transition of the test principles for UV disinfection devices from DVGW Codes of Practice to DIN standards and additional information on the currently valid documents.

According to the „Liste zulässiger Aufbereitungsstoffe und Desinfektionsverfahren“ (in German only) issued by the German Environment Agency, only UV devices whose disinfection efficacy and suitability for drinking water have been proven in a type test may be used in drinking water supplies.

For this purpose, a manufacturer submits a representative prototype of each type of UV device to be tested to a test laboratory accredited for this purpose. The type test is carried out on the basis of currently valid test principles (e.g. DIN 19294-1 or DVGW W 294-2 (A)). In the process, compliance with prescribed characteristics and the suitability of the components for drinking water are examined. The components essential for the surveillance and generation of UV radiation (device radiometer, UV lamps and lamp ballasts) are also characterized. A central component of each type test is also the biodosimetric charactization of the disinfection efficiency of the UV device. This involves determining the inactivation rate of a test organism with known UV sensitivity at different water flow rates, irradiances and water qualities (variation of UV transmission of the test water). Based on these data, the suitability and operating characteristics of the UV device are determined, for which a reduction-equivalent fluence of at least 400 J/m² (related to a wavelength of 254 nm) is maintained.

The results of the type test are documented in a test report by the test laboratory. The hygienic suitability of materials in contact with drinking water must be proven by a certificate of conformity hygiene.  Based on these documents, a type test certificate is issued by an accredited sector certifier. The certificate contains information on the test principles applied as well as the essential technical data of the UV device type concerned. In addition, the suitability and operating parameters to be complied with, consisting of maximum water flow and UV transmission or minimum irradiance to be complied with, are specified in the certificate.  

The marketing of an UV device for drinking water disinfection in the public drinking water supply is only permitted with a valid type test certificate from an accredited sector certifier. Recurring device tests of installed UV devices are not required. Even if the validity of the relevant type test certificate expires, previously installed UV devices can continue to be operated if they continue to meet the requirements of the “Liste zulässiger Aufbereitungsstoffe und Desinfektionsverfahren” of the German Environment Agency.

DIN 19294-1:2020-08 and ÖNORM M 5873-1:2020-01-01 are identical in content. The “Liste zulässiger Aufbereitungsstoffe und Desinfektionsverfahren” currently requires sector certification according to DVGW W 294-2 (A) or DIN 19294-1. A solely ÖNORM M 5873-1:2020-01-01 certification is not sufficient according to the current legal situation in Germany. However, this regulation could still change in the foreseeable future. A manufacturer can apply for recognition as DIN 19294-1:2020-08 at a sector certifier with the help of the test report. 

NOTE: This is not possible for UV disinfection units that are solely certified according to the old ÖNORM M 5873-1:2001-03-01.

The following is an overview of the currently applicable technical rules and standards for UV disinfection:
 

UV disinfection devices with UV-C LEDs do not yet have a test principle that has been included on the German Environment Agency's "Liste zulässiger Aufbereitungsstoffe und Desinfektionsverfahren" - and are therefore not yet approved for public water supplies.

The type test consists of two parts: the technical test and the test of disinfection efficiency. The following points are tested during the technical test:

• Examination of the technical documentation
• Drawing check (adherence of dimensions)
• Lamps and lamp sleeves
• Sensor attachment system
• UV radiometers
• Device and control mechanism

In the disinfection efficacy test, the suitability range and the operating range of the respective UV disinfection device is determined. The resulting operating and suitability diagrams are drawn up by the test laboratory on the basis of the microbiological efficacy tests. The characteristic curves for dimensioning and subsequent operation are the result of the test.

Control test (external audit): In order to ensure the correct manufacture of the certified test specimen, control audits must be carried out every two years on site at the manufacturer's premises. More complex tests are sometimes carried out in other periods at the test laboratories. 

Supplementary test: The certifier must be notified in advance of any changes to the test specimen submitted for the type test. Depending on the scope of the change, new partial tests, e.g. for UV lamps, may be necessary to ensure safe operation. Information on this can be found in the certifiers' rules of procedure or general terms and conditions. 

Germany, Austria and Switzerland have a conform type plate for UV disinfection devices since the publishment of DIN 19294-1:2020-08 and ÖNORM M 5873-1:2020-01-01.