Combating legionella in drinking water in the long term

The quality of drinking water contributes significantly to the quality of life and, of course, also affects health. It is all the more important to respond quickly to a legionella infestation and - even more importantly - to take the right measures to combat it. Because not every disinfection method has the same effect in every water system. We will show you how legionella develops, what they cause and how long-term control of bacteria works.

Causes of Legionella infestation in drinking water

The rod-shaped bacteria are a natural component of surface waters and also occur in groundwater and thus to a lesser extent in groundwater. It is therefore quite possible that the drinking water provided by the waterworks contains legionella. The concentration of the bacteria is significantly influenced by the water temperature. Between 25 and 45 ° C, Legionella's optimal conditions prevail, in order to multiply and endanger the hygiene of the drinking water.

The distribution is also promoted by the following causes:

  • Water pipes are used only occasionally or irregularly, so that the water stays in the pipes for a long time
  • Outdated pipes with unsuitable materials
  • Inadequate maintenance of the water system
  • Stagnant water due to oversized hot water tanks

What is the danger? Legionella out?

Legionella can cause two diseases: Legionnaires' disease and Pontiac fever. In the case of Pontiac fever, flu-like symptoms appear about two days after the transfer, but only last a few days. On the other hand, the effects of Legionnaires' disease, in which sufferers develop severe pneumonia, are much more dangerous. Without treatment, about 15% to 20% of those affected die, especially immunocompromised persons. In Germany, about 600 cases of Legionnaires' disease are reported each year. However, as not all of these diseases are associated with the bacterium, the number is probably much higher. Incidentally, transmission does not take place via drinking or eating, but via inhalation, e.g. while showering over the spray. Legionella can therefore be transmitted through all water sprinklers or water spray systems, e.g. Fountains, slides or artificial waterfalls.

Control of Legionella - chemical or thermal

There are several ways to combat Legionella. A short-term combat reaches the thermal disinfection. The temperature in the water pipes is increased via the central drinking water storage tank. The duration depends on the temperature: The water must be heated to at least 70 ° C and then leak at each sampling point for three minutes to disinfect properly thermally. This must be done in one go and must be documented. For this reason, the measure is very labor intensive and therefore expensive. In addition, most domestic water heating systems fail to provide enough hot water for this measure. In addition, thermal disinfection is often not efficient enough, e.g. if the plants allow only insufficient flow with the hot water. In these cases, a chemical disinfection is necessary. There are two methods to be distinguished here: liquid disinfectants, e.g. Hydrogen peroxide, and gaseous disinfections, e.g. Chlorine gas. Disinfection processes with sodium hypochlorite are ideal, as they are well-tolerated both for water pipes and for humans.

Prerequisites for the long-term fight against Legionella

A major problem in the efficient control of Legionella is the so-called biofilm, a layer of mucus in which various organisms live. The biofilm is thus an optimal breeding ground for the legionella and protects it immediately against disinfection measures. Also deposits of rust or lime promote the legionella settlement.

Therefore, the following factors must be fulfilled for a long-term fight against Legionella:

Intensive disinfection over a long period of time

Resistant disinfectant that attacks the biofilm and removes it together with the Legionella

  • It is therefore not sufficient if the disinfection is simply carried out with a high chemical concentration. In these cases, a new spread of the bacteria is very likely.
  • Sustainable anti-legionella control by the specialist company

In the event of an infestation with Legionella, you should definitely commission a certified specialist for hygiene and drinking water protection, or more specifically, a SHK specialist certified in accordance with VDI 6023. Not only does it guarantee reliable control of legionella, it also analyzes the causes of bacterial spread. For which disinfection method is used depends on the cause. After all, the Legionella should disappear from the lines in the long term, so that a consistently high drinking water hygiene is guaranteed.

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