What is Legionella?

Legionella pneumophila is the originator of the much-feared Legionnaires' disease. Single, free living legionella bacteria however do not present any risk to the user. But if the circumstances (such as the temperature, the presence of biofilm, nutrients and other factors) are ideal, these bacteria may multiply very quickly. In large volumes (>1000 kve/l) these bacteria are in fact very dangerous. Legionella prevention must consequently be based on a thorough analysis mapping all risk factors and on executing management measures (such as adjustments of the mains concept, combined with a continuous, preventive disinfection).

Can Legionella also be found in cold water ?

Extensive measuring campaigns (VROM, Netherlands) show that Legionella can often be found in the cold-water circuit as well as in the hot-water circuit. It was found, for instance, that 48 % of the studied swimming-pools were contaminated, of which 89 % had been contaminated through cold water. It also turned out that 10 % of the studied hotels were contaminated and in 88% of these cases the contamination was situated in the cold water. Measuring campaigns further show that, especially in hot summers, cold water may rise to a temperature of 25°C or above. What is more, in hospitals and nursing homes the often historical mains water system (branching off everywhere in cellars and in less often used rooms) tends to prevent an efficient tackling of biofilm and its associated microbial contaminations, such as Legionella.

What about legislation and Legionella ?

Since December 2002 the Belgian Legionella Decision imposes certain obligations on risk institutions (such as hospitals and nursing homes) concerning the prevention and the combat of Legionella in the water mains.