Some conditions that are known to cause Legionella proliferation include: scale deposits or algae growth in water, water stagnation in pipes, low temperatures and stratification in water heaters and inappropriate water treatment. Oftentimes it is thought that Legionella cannot form in well-circulated water systems, but that is not the case. In fact, Legionella bacterium can be found in many recirculating hot and cold water systems, and is especially common in large, complex water systems found in hospitals, hotel, and office buildings. An exaberating factor in these complex systems is scale deposits and biofilms that can serve as breeding grounds for Legionella bacteria.
Scale, which can be defined as “a hard, rocklike deposit of calcium or magnesium salts,” can form in any water system, but its development is especially aggravated by heat and hard water concentration. Scale buildup can perpetuate water system problems and increase risk for Legionella bacteria because it impedes heat transfer and obstructs water flow and cooling, creating a prime environment for Legionella to develop.
Outside of the main water system, scale can also develop in and around water taps. When the surrounding temperature is high, it becomes especially difficult for disinfectants to penetrate the scale and eliminate the Legionella bacteria. Furthermore, it is likely that the bacteria will return because its ideal breeding ground has not been eliminated. Additionally, longstanding deposits of biofilm like this provide nutrients for Legionella growth than can lead to odor and taste problems in the water system.
The best way to reduce scale and biofilm buildup development-and in turn reduce the risk of Legionella bacterium in your water system-is to complete a risk assessment of the water system in question. Once risk areas and problems have been identified, a set of measures to reduce development of bacteria-hosting scale and biofilm will need to be put in place. In areas with hard water, an especially aggressive system may need to be put in place. In any water system, however, an effective plan will work to control scale deposition and include a water treatment system that prevents growth of biofilms and Legionella bacterium.