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Cooling towers and Legionella
Cooling Towers and Legionnaires’ disease: Control, Monitoring and Prevention
Recent cases of Legionnaires’ disease have highlighted the need for cooling towers used in conjunction with large HVAC systems and industrial cooling processes to be appropriately maintained and monitored.
What is Legionnaires’ disease?
Legionnaires’ disease is a severe infection of the lungs not dissimilar to pneumonia. It is caused by bacteria of the Legionella family, specifically Legionella pneumophila, which can be present in air conditioning cooling towers, spas and similar bodies of water. One becomes infected by inhaling the bacteria, after which it takes anywhere from two to 10 days to become sick.
Legionnaires’ disease is a severe infection of the lungs caused by bacteria of the Legionella family
Legionella in cooling towers
Legionella pneumophila bacteria can grow to high numbers in warm, stagnant water. Outbreaks are sometimes associated with contaminated cooling towers. Legionella thrive in this environment due to a number of factors, specifically:
- Stagnant water
- Warm temperatures
- Nutrient availability
These conditions are often caused by a deficiency in the maintenance of the cooling tower. Regular inspections, disinfection and maintenance of cooling towers and plumbing systems is the only way to limit the growth of the Legionella bacteria.
Regular inspections, disinfection and maintenance of cooling towers and plumbing systems is the only way to limit the growth of the Legionella bacteria
Effective water treatment for cooling towers
A key objective of any effective water treatment program for cooling towers should look to control and limit:
- corrosion
- scaling
- fouling
- microbial growth, including the growth of Legionella
Ideally any water treatment plan should be done under the auspices of a risk assessment management plan. Additionally the water treatment system should look to manage some specific aspects of water quality, namely:
- Conductivity/TDS
- ORP with satisfactory level for disinfection
- pH correction – always below 8.00
- and programmable chemical additives – such as inhibitors, biocides, dispersants, etc.
Modern programmable controllers enable all of these functions, and also have the additional advantage of monitoring these indicators 24/7 using remote access via an internet connection. This can provide real time alerts for scaling, corrosion, or alert the operator if anything is not working properly – such as the disinfection chemicals or an increase in ORP levels.
CHEMTROL® fully featured range of Programmable Controllers are suitable for Cooling Tower applications and come with an industry-leading 5 year electronics warranty.
