Managing legionella risks: essential steps for safety in cooling towers and water systems
A recent outbreak of legionnaires’ disease in Victoria has been linked to a contaminated water source – a cooling tower in Laverton North in Melbourne's west. There are more than 100 confirmed cases of the bacterial infection with the vast majority being hospitalised - one person died after contracting the disease.
Although the contamination is now considered under control, and no warnings have been issued for other states, it is a reminder for PCBUs (Persons Conducting a Business or Undertaking) and building owners to ensure their air handling and water systems are properly maintained to prevent legionella bacteria from growing and spreading.
Understanding legionella bacteria
Legionella bacteria is found in the environment. Human infection is most commonly caused by legionella pneumophila found in man-made water systems such as cooling towers and spas which can cause legionnaires' disease – a severe respiratory illness with pneumonia.
Where is it found in workplaces?
Legionella bacteria can be found in a variety of water handling systems, at temperatures ranging from 5 to 60 degrees celsius. At a workplace, legionella has been found in water linked with the following pieces of equipment:
- Air conditioning cooling water systems that include components such as a cooling tower, closed circuit fluid coolers or evaporative condenser, associated chiller and condenser
- vehicle wash systems
- horticultural misting systems
- misting systems in supermarket fruit and vegetable displays
- emergency showers
- eyebaths and face-wash fountains
- sprinkler and hose reel systems
- air washers
- wet scrubbers, particle and trivial gas scrubbers
- industrial process water systems
- portable water systems and spa pools at hotels.
Essential steps to managing legionella risks
- Regular maintenance — ensure that all air handling and water systems are routinely inspected and maintained to prevent conditions conducive to legionella growth.
- Temperature control — keep hot water systems at temperatures above 60°C, and cold water systems below 20°C to inhibit the growth of legionella bacteria.
- Clean and disinfect — regularly clean and disinfect cooling towers, hot water systems, and other relevant water systems according to industry guidelines.
- Monitoring and record-keeping — implement a monitoring program to check for legionella bacteria and keep detailed records of maintenance and disinfection activities.
Further information
For comprehensive guidance on controlling legionella in cooling water systems and related environments, refer to the Guide to legionella control in cooling water systems, including cooling towers (PDF, 0.46 MB).
For more information on legionnaires’ disease, visit Queensland Health’s website or call 13HEALTH (13 43 25 84). If you suspect exposure to Legionella bacteria, seek advice from your doctor or local public health unit promptly.