Legionella

Legionnaires disease is an acute respiratory infection caused by the Legionella pneumophila bacteria which may cause a broad spectrum of diseases - from mild cough and fever to serious pneumonia.

The bacteria thrives in temperatures ranging 69 ^oF (20.5 ^oC) to 122 ^oF (50 ^oC) and can be traced in water supply systems, central heating systems and air conditioning systems.

Note! Any water system with an operating temperature between 69 ^oF (20.5 ^oC) and 122 ^oF (50 ^oC) is a potential legionella source. Special attention should be taken for

• cooling towers and evaporative condensers
• scrubber systems with low temperatures
• low temperature hot water supply systems

Regularly cleaning, heat and chemical treatment are often necessary to avoid the potential development of the bacteria.

• keep basins and sumps free of mud and organic debris
• use chemical and organic inhibitors where recommended
• avoid water stagnation - circulate the water through the system
• avoid leaks from processes to the cooling water - process water may contain nutrients that may feed the bacteria

The Legionella bacteria cannot survive water temperatures above 131 ^oF (55 ^oC) for more than five or six hours. Instantaneous destruction of the bacteria occurs at temperatures above 158 ^oF (70 ^oC). General protection against the bacteria in hot water systems can be achieved by designing operating water temperatures to be at least 140 ^oF (60 ^oC). Note! - be aware of scalding. Tap water delivered at 140 ^oF can cause a full-thickness burn in 10 seconds. Hot water should always be mixed down to lower temperature before the tap.

For water temperatures below 140 ^oF (60 ^oC) special procedures are required regarding cleaning and chemical treatment.