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 Bacillus subtilis and 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 DIN 19294-2). 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 (referred to the organism Bacillus subtilis and 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.

With the publication of the test standards for UV disinfection devices equipped with medium pressure UV lamps, DIN 19294-2:2026-04 and DIN 19294-4:2026-04, following the publication of DIN 19294-1 and DIN 19294-3 in 2020, the DVGW technical rules DVGW W 294-2 (A) and DVGW W 294-3 (A) have been completely replaced.

As shown in the overview below, the previous DVGW documents for the respective UV lamp technologies have been split across several DIN standards.
 

As part of the revision of the DVGW technical rules of 2006, a number of significant changes have been made in order to reflect the current state of the art.
Below is a summary of the most important changes from the DVGW technical rules to the relevant DIN standards.

DIN 19294-1:2020-08 – Devices equipped with UV low pressure lamps – Requirements and testing

• Covers the complete testing procedure for UV disinfection devices equipped with low-pressure UV lamps
• Includes content that was previously spread across DVGW technical rules DVGW W 294-1 (A), DVGW W 294-2 (A) and DVGW W 294-3 (A)
• Additions and amendments:
  • Technical characterisation of UV lamps and lamp control units
  • Addition of device radiometer requirements and testing from DVGW W 294-3 (A)
  • Adjustment of radiometer requirements (linearity, directional sensitivity, temperature sensitivity, …)
  • Adaptation of biodosimetry (addition of an operational scenario to the H and L scenarios; update of the characterisation and criteria for the test organism, …)

DIN 19294-2:2026-04 – Devices equipped with UV medium pressure lamps – Requirements and testing

• Covers the complete testing procedure for UV disinfection devices equipped with medium-pressure UV lamps
• Includes content previously spread across DVGW W 294-1 (A), DVGW W 294-2 (A) and DVGW W 294-3 (A)
• Additions and amendments:
  • Technical characterisation of UV lamps and lamp control units
  • Addition of device radiometer requirements and testing from DVGW W 294-3 (A)
  • Adjustment of radiometer requirements (linearity, directional sensitivity, temperature sensitivity, spectral selectivity, …)
  • Adaptation of biodosimetry:
    • New test approach based on the US Environmental Protection Agency’s guidance document, the so-called combined variable method, from the UVDGM
      (WRIGHT, H., M. HEATH, T. BROOKS, AND JEFF ADAMS. Innovative Approaches for Validation of Ultraviolet Disinfection Reactors for Drinking Water Systems. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-20/094, 2020)
    • Flexible testing of a wide dynamic range instead of the previous rigid H and L scenarios
    • Change of test organism to MS2 phage based on new scientific findings regarding the spectral sensitivity of Bacillus subtilis
      (SCHWARZENBERGER, Verification of a Combined Variable Approach for the microbiological Validation of Monochromatic- and Polychromatic UV Systems, Karlsruhe 2025)
    • Conversion of results to represent the applicable reduction-equivalent fluence of 400 J/m², relative to Bacillus subtilis and 254 nm

DIN 19294-3:2020-08 – Reference radiometers for devices equipped with UV low pressure lamps – Requirements and testing

• Covers the full range of tests for reference radiometers used in UV disinfection devices equipped with low-pressure UV lamps
• Adaptation of radiometer requirements (linearity, directional sensitivity, temperature sensitivity, measurement uncertainty and calibration, etc.)

DIN 19294-4:2026-04 – Reference radiometers for devices equipped with UV medium pressure lamps – Requirements and testing

• Covers the full range of tests for reference radiometers used in UV disinfection devices equipped with medium-pressure UV lamps
• Adaptation of radiometer requirements (linearity, directional sensitivity, temperature sensitivity, spectral selectivity, measurement uncertainty and calibration, etc.)

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.

The EU RoHS Directive 2011/65/EU (“Restriction of Hazardous Substances”) regulates the circulation of hazardous substances in electronic devices within the EU. These include lead, mercury, cadmium and chromium(VI). All UV low-pressure and UV medium-pressure lamps used in Germany contain mercury. The technology of so-called gas discharge lamps utilizes the property that mercury emits disinfecting UV-C radiation when excited (inactivation of microorganisms).

According to the EU RoHS Directive, the distribution of gas discharge lamps is already prohibited in the EU, but there are temporary exemptions in Annex III of this Directive. Low-pressure UV lamps with up to 15 mg mercury are still permitted under Annex III, 4(a)-I and medium-pressure UV lamps are still permitted under Annex III, 4(f)-IV. If no requests for extension have been submitted by August 24, 2025, both exemptions will expire on June 30, 2027. If this happens, these types of gas discharge lamps may no longer be placed on the European market. DVGW e. V. has already expressed criticism in the past that the mercury content in UV low-pressure lamps was set per lamp and not linked to the lamp output.

For a long time, there was a misunderstanding within the water sector that UV devices and their individual UV lamps were excluded from RoHS as large-scale fixed installations. The requirements for large-scale fixed installations are listed in the “FAQ key guidance document - RoHS” document on the European Commission's website. 

At present, UV-C LEDs – as a future alternative technology – have a lower power density than UV low-pressure and UV medium-pressure lamps. Furthermore, the radiation geometry differs from that of mercury discharge lamps, which requires a different reactor design. Retrofitting, as has been the case with conventional room lighting lamps, is therefore not possible (see DINoLED final report, German version only). The technology and in particular the efficiency of UV-C LEDs has made significant progress over the past ten years. DVGW e. V. is committed to ensuring that certified UV-C LED disinfection equipment is available on the European market in the medium term.