Proper operation of cold drinking water installations

Process model for the propagation of legionella

Some of the most unfavourable boundary conditions exist across the drinking water distribution chain. The regulations do not specify what normal operation of a drinking water installation is in terms of the microbiology. The aim of the project was to develop a process model for the growth of Legionella in cold drinking water installations and to define the requirements for proper operation.

In the DVGW-research project “Legionella in cold water”, extensive investigations were carried out under laboratory conditions, with drinking water model installations as well as in installations of buildings. As a result, approaches for the reproduction process of Legionella in the drinking water system were concluded. It was shown that the legionella concentration in a system is significantly determined by the factors temperature, biofilm composition, flow profile and nutrient content of the materials used. A reproduction of Legionella only takes place in amoebae at a temperature of >25°C. At temperatures of >25°C, the velocity at which legionella multiplies and also the maximum concentration depends on the system conditions. The biofilm composition is of particular relevance, as it influences the reproduction velocity of the amoebae through the nutrient supply. As a result, conclusions for the regulations were derived, which can be used as a basis for their further development. In addition, the results can also be used in practice to derive and evaluate measures to prevent the reproduction of Legionella in drinking water installations.


Korth, A.; Petzoldt, H.: DVGW-Forschungsvorhaben untersucht Vermehrung von Legionellen im Kaltwasser. DVGW energie/wasser-praxis 05/2020, 34-40 (2020)

Publication series Volume 89: Increase of legionella in cold water
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