Legionella
Legionella pneumophila - bacterium that thrives in water supply and air conditioning systems - causing Legionnairs disease
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Legionnaires' disease is an acute respiratory infection caused by the bacterium Legionella pneumophila bacteria. The bacteria can cause a broad spectrum of disease from mild cough and fever to serious pneumonia.
The bacteria thrives at temperatures between 69 oF (20.5 oC) and 122 oF (50 oC) and may be traced in water supply, central heating and air conditioning systems.
Note! Any water system with operating temperatures 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 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 can be achieved by designing an operating water temperature of at least 140 oF (60 oC).
For water temperatures below 140 oF (60 oC) special initiatives are necessary regarding cleaning and chemical treatment procedures.
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Related Topics
- Physiology - Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more
- Water Systems - Hot and cold water systems - design properties, capacities, sizing and more
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