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Legionella control

Killing and fighting Legionella

The outbreaks of Legionella in Warstein 2013 and Jülich 2014 have shown it. Evaporative cooling systems (42. BImschV.) can be a source of dangerous infections. But cooling towers are not the only source of infection. Whether fountains (DIN SPEC 31062), wet separators (42nd BImschV) or drinking water systems (TrinkwV). Wherever water is finely atomized and aerosols are formed, dangerous Legionella can spread through the air.
Here we answer the most important questions about Legionella.

Whether drinking water, cooling tower, fountain or wet separator. They all carry the risk of becoming the source of Legionella infections. Because the circulating water has an optimal temperature for the reproduction of these bacteria and offers a rich food supply due to its contact with the atmosphere. This is why the legislator prescribes specific measures to protect the population in all these areas. The aqua-concept and the water treatment layer offer you individual solutions for prevention and emergencies.


What are Legionella?
Legionella are a genus of rod-shaped bacteria from the family Legionellaceae. They are water-borne, non-spore-forming bacteria that move through one or more scourges. Currently, more than 48 species and 70 serogroups are known.
Legionella multiply within host cells (e.g. amoebae). These are actually natural predators of Legionella. But Legionella turn the spit around. They grow in the amoeba until they fill it completely. The amoeba bursts and distributes the reproduced Legionella in the environment. They can be regarded as potentially pathogenic to humans. The most important species for human diseases is Legionella pneumophilia. It is the pathogen that causes legionellosis or Legionnaire's disease.
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How dangerous are Legionella bacteria in drinking water?
The Robert Koch Institute assumes that around 4% of pneumonia in Germany that was not acquired in hospitals can be traced back to a Legionella infection. The mortality rate is estimated at up to 10%. It must therefore be assumed that around 3,000 deaths occur every year. This corresponds approximately to the number of road deaths per year in Germany. Back to the table of contents


How can one become infected with Legionella?
The main route of infection is inhalation of water droplets during fogging from hot water. Thus, showers in particular, but also aerosols at the tap, humidifiers, air conditioners and cooling towers are sources of danger. Wound infections are extremely rare and normal eating and drinking is also possible. Infections can only occur if water containing pathogens enters the windpipe. A transmission from person to person is excluded so far.
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What does the Drinking Water Ordinance say about Legionella?
The Drinking Water Ordinance (TrinkwV) obliges home owners and administrators to operate drinking water installations in a defect-free condition at all times, without impairing hygiene. This is a contractual and legal obligation.
The Drinking Water Ordinance regulates the obligations of property managers and other property owners if the technical measure value for Legionella in drinking water is exceeded. In the event of a case, the ordinance requires the preparation of a hazard analysis. This provides a concrete inventory of planning, construction or operational deficiencies that have led to the Legionella problem. It helps the owner/operator to take effective countermeasures and to coordinate these depending on the degree of health hazard to the occupants. Back to the table of contents


Are there any legal consequences if the Drinking Water Ordinance is not observed?
If Legionella contaminated water is deliberately or negligently released, this is a criminal offence according to § 24 of the Drinking Water Ordinance, which can be punished with imprisonment for up to 2 years. Fines of up to € 50,000 will also be imposed for investigations not carried out in good time or in the proper manner, violations of the duty to document or provide information, and much more. Back to the table of contents


How do Legionella develop in drinking water installations?
Legionella often occurs at a water temperature between 25 °C and 55 °C and is often found in stagnant water.
- Missing hydraulic balancing
- Insufficient insulation of hot and cold water pipes
- Reduced flow temperature
- Stagnation due to overdimensioning/water saving by users or in the event of vacancy/long-term absence of residents, e.g. holiday homes
- Lime and sludge deposits in hot water storage tanks and pipelines promote the occurrence of Legionella.
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How can Legionella be combated in concrete terms?
If the limit values of the Drinking Water Ordinance for microbiological parameters in a drinking water installation are exceeded, the microbial contamination must be eliminated immediately. Legionella and other microorganisms can be successfully eliminated by targeted cleaning of the pipes with thermal or chemical disinfection. However, individual measures are often not sufficient. The structural differences usually require an individual action plan which includes regular preventive measures such as pipe network flushing or the installation of an ultrafiltration plant. Back to the table of contents


What is thermal disinfection?
In the case of Legionella infections, thermal disinfection is still considered the best disinfection method in many places today. In principle, it is easy to carry out and requires no chemicals at all. To a certain extent you can control the microbial danger with it. However, the method is often not sufficient to remove Legionella completely and effectively from the plant.
The principle of thermal disinfection is simple: Legionella can no longer multiply at temperatures of 55 °C and above. Therefore each tapping point is rinsed with over 60 ?C hot water. The germs die at this temperature. The problem: In order to ensure that Legionella is killed, the taps must be rinsed with hot water for at least three minutes. With large objects and plants this can take place only step by step (strand-wise). And: Most drinking water heaters are not designed for this continuous operation and cannot reach the required temperatures.
Disadvantages of thermal disinfection: During thermal disinfection, the material of the drinking water installation is heavily stressed. Weld seams, solder joints, seals or cover layers are strongly attacked. Due to the high temperatures, more lime precipitates and deposits in the pipes. In addition, the pipelines are more susceptible to corrosion. Back to the table of contents


What is chemical disinfection?
Disinfection with chlorine-free chlorine dioxide systems is particularly effective and sustainable. Here, highly reactive chlorine dioxide is filled fully automatically into the on-site water system. This also effectively removes the biofilm that has settled in the pipes. In contrast to chlorine, it does not reduce its disinfection effect with increasing pH value and is very effective at low concentrations. It is important that the disinfectant can reach all areas of the contaminated system in order to have a direct effect on the germs.
Advantages and disadvantages of chemical disinfection: The decomposition of the biofilm in the system kills the Legionella bacteria safely and without the formation of odours. However, the improper use of chemicals can lead to undesirable by-products. For the chemical disinfection method, the process must therefore be documented in detail by professionals. Back to the table of contents


What is a Legionella circuit?
The so-called Legionella circuit is a periodic, thermal disinfection. It heats the drinking water heater and the entire hot water pipe network, including the tap fittings, to over 70 °C for at least 3 minutes in a defined cycle. It is important that all outlet fittings are open. Only then can the circuit function. This process cannot therefore be carried out automatically. And: All branch lines and connections through which the heated water does not flow are also not disinfected. Heating can therefore only be a preventive measure and has no effect on already contaminated systems. Back to the table of contents


Are there immediate measures to be taken in the event of a Legionella infestation?
Terminal Legionella filters interrupt the transmission of Legionella from water to humans. They offer immediate safety with highest flexibility and do not require long-term investments. For use in the removal of Legionella and pathogens, the filter consists of pores with a maximum diameter of 20 nanometers. The blocking of showers and water taps from a finding value of 10,000 CFU can be lifted after consultation with the health authorities by using the terminal water filters. The installation of the filters can be carried out by the users themselves due to the simple installation.
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What are the legal requirements in connection with Legionella?
The amended Drinking Water Ordinance has been in force since January 2018. Home owners and operators now not only have clearly defined requirements. They are also under time pressure. From now on, the laboratories will report germ excesses directly to the health authorities. In order not to endanger the health of the citizens, the new Drinking Water Ordinance requires an annual examination for Legionella. Even if cold water is supplied to third parties, e.g. through drinking water wells, annual tests for parameters such as microbiology and heavy metals are required. If the Drinking Water Ordinance is not correctly complied with, shower bans and legal consequences may arise.
The 42nd BImSchV contains concrete requirements for the hygienic operation of evaporative cooling systems, cooling towers and wet separators. Among other things, there is an obligation to notify all new and existing plants as well as the obligation to prepare hazard assessments including action plans if limit values are exceeded even before the plant is put into operation by hygienically competent personnel.
DIN SPEC 31062 regulates the planning and operation of fountains. This specification applies to all fountains which are operated with water, sea water, mineral water, medicinal water, brine (also artificially produced) or thermal water. Back to the table of contents


What exactly does the Drinking Water Ordinance prescribe?
- Laboratories are legally obliged to send positive results directly to the responsible health authority.
- The accredited laboratories must supervise the analysis and sampling.
- This means that the laboratories must cooperate with companies that are integrated into the quality management system for sampling.
- The initial inspection for the implementation of the Drinking Water Ordinance for newly built facilities must be carried out within the first 3 - 12 months after completion.
- The term "hazard analysis" is clearly defined in the new guideline VDI/BTGA/ZVSHK 6023-2.
- Hazard analyses that do not comply with VDI 6023-2 are no longer recognised by health authorities.
- No physical or chemical processes may be used which are not intended for drinking water supply.
- Substances or objects already introduced and processes used may continue to be used up to two years after this Ordinance comes into force.
- Permanent disinfection or other unconventional solutions are thus excluded.
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What are the test procedures?
The drinking water from the water supplier is generally perfect and has a pH value between 6.5 and 9.5 when leaving the waterworks. This corridor of the pH value is prescribed by law. However, on the way from the house feed to the tapping point, the drinking water can be contaminated by various contaminants. Especially pipe systems, pipes and water taps are often a source of contamination with heavy metals or bacteria. The drinking water quality is analysed with a drinking water analysis and possible contamination of the drinking water, e.g. with Legionella, is determined. With a bacteria rapid test, anyone can identify and quantify numerous pathogens reliably and unambiguously. Such tests are recommended as an early warning system for random samples after reconstruction measures in the object, in case of suspicion of contamination and in case of health protection concerns.
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What is the permissible number of Legionella bacteria in drinking water installations?
Under favourable conditions, Legionella bacteria multiply twice within three hours. In order to minimize the health risk of the user and to ensure perfect drinking water hygiene, the recommended target value is "0" CFU/100 ml. However, sampling drinking water at the specified tapping points is only a snapshot of the drinking water system. Regular examinations are therefore an absolute must.
In the case of legionella counts above 100 CFU/100 ml, the technical measure value according to the Drinking Water Ordinance has been exceeded, so that the contractor and the other owner of the drinking water installation must fulfil the obligations from § 16 para. 7 Drinking Water Ordinance (hazard analysis). For hazard values >10,000 CFU/100 ml and above, immediate measures to avert danger such as a ban on showering or the use of terminal Legionella filters are also necessary. Back to the table of contents


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Dr. Andreas Detig
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Phone: +49 089 899 369 0
E-mail: a.detigaqua-concept-gmbh.eu