Legionella in drinking water: causes, risks and protective measures

Legionella in drinking water are a serious health risk that particularly affects homeowners, landlords and operators of public facilities. These bacteria can cause Legionnaires' disease, a potentially serious form of pneumonia. There is a widespread misconception that Legionella bacteria are dangerous when drinking contaminated water. In fact, people become infected by inhaling tiny droplets of water (aerosols) containing Legionella. A classic scenario is the shower, where such aerosols can easily form.

Health risks due to legionella

Legionnaires' disease often manifests itself with flu-like symptoms such as fever, coughing and muscle aches. It is particularly dangerous for people with a weakened immune system, such as the elderly or small children, where it can lead to life-threatening pneumonia. In Germany, an estimated 2,000 people die each year as a result of this infection. The actual number of infections is difficult to determine, as the symptoms are often confused with those of flu and not every case is diagnosed.

Legal requirements and preventive measures

Since the end of 2011, the Drinking Water Ordinance in Germany has stipulated that landlords must have a legionella test carried out every three years. This regulation aims to detect and prevent legionella outbreaks at an early stage. In the event of positive findings, tenants may even be banned from showering in their apartments until the problem has been rectified.

Raising the temperature as a short-term measure

A common method of combating legionella in the hot water system is to increase the water temperature to over 60°C. This temperature kills legionella bacteria. This temperature kills legionella, but also has some risks and disadvantages. Firstly, there is a risk of scalding for the residents. Secondly, this measure is not always reliable as it requires the entire water system to be heated evenly, which is not always guaranteed. In addition, the higher temperature results in increased energy costs, especially for systems that are operated with solar technology. Here, the water, which is normally heated to 40-50°C, must be brought to the required 60°C using additional energy.

Chemical disinfection and its limits

Another method is chemical disinfection, in which chlorine or other disinfectants are used. However, this method is controversial as legionella is relatively resistant to many chemicals. In order to kill them effectively, high concentrations are often necessary, which can exceed the permitted limits. In addition, such chemicals can be harmful to health and must be carefully dosed and monitored.

UV-C disinfection: an effective and safe solution

In view of the uncertainties and disadvantages of the above-mentioned methods, the UV-C disinfection offers a reliable and environmentally friendly alternative. UV-C light has the ability to destroy the DNA of microorganisms such as legionella, rendering them inactive and unable to multiply. This method is particularly effective as it is used directly in the water cycle and leaves no chemical residue.

How UV-C disinfection works

In a UV-C disinfection system, the water is continuously passed through a chamber in which it is irradiated with UV-C light. This light destroys the DNA of the legionella bacteria, rendering them harmless. A major advantage of this method is that it works independently of the water temperature, so there is no risk of scalding. In addition, the energy consumption is comparatively low, which also makes it economically attractive.

Areas of application and advantages

UV-C disinfection systems are suitable for single-family homes as well as large residential complexes or public buildings. They are easy to install, require little maintenance and are cost-effective to operate. Another advantage is their environmental compatibility, as no harmful chemicals are released into the environment. This also avoids the problem of chemical residues in waste water.

Long-term prevention strategies

In addition to the installation of a UV-C disinfection system, there are other measures that can help to prevent legionella in drinking water:

1. Regular maintenance and cleaning Hot water systems should be regularly maintained and cleaned to prevent deposits and biofilms that can serve as a breeding ground for legionella.

2. Optimizing the water temperature Although high temperatures kill Legionella, the water temperature in hot water systems should be set to inhibit the growth of bacteria without causing scalding. A temperature of around 55°C can be a good compromise.

3. Systematic check Regular microbiological testing of the water can help to detect legionella at an early stage and take appropriate measures.

4. Training and education Raising awareness is an important step towards prevention. Residents and users of buildings should be informed about the risks of legionella and the importance of water hygiene.

Conclusion: Safety and health through preventive measures

Legionella in drinking water is a serious problem that can be effectively combated through a combination of legal requirements, technical solutions and preventative measures. UV-C disinfection offers a safe, efficient and environmentally friendly method of minimizing the risk of legionella infection. Together with regular maintenance and monitoring, these measures can help to ensure the health and safety of residents.