Legionella Control and Prevention


The illness of the Legionary was discovered in July 1976 when a pneumonia epidemic affected veterans of the American Legion during their annual congress that took place in Philadelphia. There were 4400 participants, 182 veterans fell ill (pneumonia) and 29 died.

The agent responsible for the appearance of this disease was a bacteria, until then unknown, and therefore was given the name of Legionella pneumphila. After reviewing what happened the researchers found that there was a bacteria in the air conditioning system of the Hotel.

From then on, many more cases have been found in many places with the common factor that the disease is directly connected with several water systems.

That’s why there are several laws that include the systems that should always be treated in order to control the possibility of generating the Legionnaire’s disease.

The origin of the Legionella outbreaks notified during the decade form 1999/2009 in %, following what was published by  the Centro Nacional de Epidemiologia del Instituto de Salud Carlos III (11/2010)

As we see in the graphic, despite what is generally believed, the most frequent focus of Legionella outbreaks are the sanitary water systems.

Actually there is a much stronger conscientiousness about the importance of controlling this bacteria, so the illness doesn’t spread affecting people, and most of the countries have developed a specific legislation in order to avoid it’s proliferation and minimize the number of cases.

In Spain there’s a Royal Decree that covers the whole nation, RD 865/2003, different autonomic legislation and, even, a technical guide has been developed (in 2007) that tries to facilitate the implementation of the different measures that have to be applied, once the risk associated with every water system has been evaluated. The actual legislation establishes that the installations that can pose risk of generating  Legionella outbreaks, are the following.

  • Cold and hot water systems in industries, hospitals, hotels, residence for the elder people, sport areas.
  • Jacuzzis or whirlpool baths
  • Humidifiers
  • Cooling Towers
  • Water Deposits
  • Ornamental Fountains
  • Any other water system that could spray water

Sanitary water systems (cold and hot), including their different elements: tubes and ducts, tanks, taps, other water end points, etc.


There are different approaches to control the appearance and spread of Legionella pneumophila. The previous steps are:

  • Inspection of the water systems
  • Make a thorough APPCC analysis that will include the preventive or corrective measure for each water system
  • Evaluate the risk of each system trying to use objective measures
  • Perform the needed treatment for each system
  • Certificate the treatment done
  • If necessary carry on follow up inspections or create the registers that will demonstrate that they’re done
  • Analyze the water of the water systems

All this is done in order to achieve what the Real Decreto 865/2003 and the Decret de la Generalitat de Catalunya 352/2004 state.

There are different possible preventive measures that can be taken and especially there are different ways to treat a water system.

How to

Although there are different ways of treating and controlling Legionella in water systems we will generally use the following:

  • Using heating techniques. This control method is based on increasing the temperature of the water systems, specially of those that carry  sanitary hot water.
  • Using chlorine. By adding chlorine into the water systems we can kill Legionella. This method is widely used in cold water systems, jacuzzis (also Bromine can be used), water deposits, ornamental fountains, or irrigation systems. The use of chlorine, bromine or other biocides is also common in cooling  towers and humidifiers.
  • Using chlorine dioxide. Chlorine dioxide is used to disinfect drinking water and can be used in protecting any kind of water system. ClO2 is very efficient even in heavily polluted waters and is pH independent. More than 99% of the bacteria live in the biofilm, so decontaminating the biofilm is the key to success. ClO2 acts directly over the biofilm and eliminates it.   More Information.

Differences between biocides

Efficacy of the biocide Persistence Corrosion
Ozone ++++ + ++++
Chlorine/Bromine ++ ++ +++
Chlorine Dioxide +++ +++ ++
Cloramine + ++++ +


What do we offer?

We don’t just control Legionella but help you identify what can be done to control and manage the pathogens that could exist in your water systems

We can fulfill all the legal requirements and help you do it in an easy way.

We don’t just stick to one possible type of treatment but we can offer you the best option to cover your needs.

Since we offer different possibilities we not only have a technical answer to each situation but also can offer an economical approach.

Technical Personnel equipped with all the necessary equipments to perform their duty

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