Legionella in drinking water: causes, risks, and protective measures

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

Health risks from Legionella

Legionnaires' disease often manifests with flu-like symptoms such as fever, cough, and muscle pain. It is particularly dangerous for people with weakened immune systems, such as the elderly or young children, where it can lead to life-threatening pneumonia. In Germany, an estimated 2,000 people die annually from the consequences of this infection. The actual number of infections is difficult to determine because the symptoms are often mistaken for those of the flu and not every case is diagnosed.

Legal requirements and preventive measures

Since the end of 2011, the Drinking Water Ordinance in Germany requires landlords to conduct a Legionella test every three years. This regulation aims to detect and prevent Legionella outbreaks early. In the case of positive findings, tenants may even be prohibited from showering in their apartments until the problem is resolved.

Temperature increase as a short-term measure

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

Chemical disinfection and its limitations

Another method is chemical disinfection, where chlorine or other disinfectants are used. However, this method is controversial because Legionella is relatively resistant to many chemicals. To effectively kill them, high concentrations are often necessary, which can exceed permissible limits. Moreover, such chemicals can be harmful to health and must be carefully dosed and monitored.

UV-C disinfection: An effective and safe solution

In light of the uncertainties and disadvantages of the aforementioned methods, UV-C disinfection offers a reliable and environmentally friendly alternative. UV-C light has the ability to destroy the DNA of microorganisms like Legionella, rendering them inactive and unable to reproduce. This method is particularly effective as it is applied directly in the water cycle and leaves no chemical residues.

Functionality of UV-C Disinfection

In a UV-C disinfection system, water is continuously passed through a chamber where 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, thus eliminating the risk of scalding. Additionally, the energy consumption is comparatively low, making it economically attractive.

Areas of Application and Advantages

UV-C disinfection systems are suitable for both single-family homes and large residential complexes or public buildings. They are easy to install, require little maintenance, and are cost-efficient 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 wastewater.

Long-term Prevention Strategies

In addition to installing a UV-C disinfection system, there are other measures that can help prevent Legionella in drinking water:

1. Regular Maintenance and Cleaning : Hot water systems should be regularly maintained and cleaned to avoid deposits and biofilms that can serve as a breeding ground for Legionella.

2. Optimization of Water Temperature : Although high temperatures kill Legionella, the water temperature in hot water systems should be set to inhibit bacterial growth without causing scalding. A temperature of about 55°C can be a good compromise.

3. Systematic Monitoring : Regular microbiological tests of the water can help detect Legionella early and take appropriate measures.

4. Training and Education : Raising awareness is an important step in 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 regulations, technical solutions, and preventive measures. UV-C disinfection offers a safe, efficient, and environmentally friendly method to minimize the risk of Legionella infection. Together with regular maintenance and monitoring, these measures can help ensure the health and safety of residents.