An outbreak of legionella makes a compelling news story, gets wide circulation and is always branded as a serious public health concern. The negative publicity this disease can generate for an organisation is far-reaching, not to mention the repercussions for non-compliance with regulations.
Over 400 cases of legionella are reported in Australia every year, with approximately half of these originating from contaminated water systems. This blog will help keep you as a water treatment specialist, and your customers, in the shallow end and explains how you can systematically navigate the deep waters of controlling legionella bacteria in cooling towers.
What causes legionella in cooling towers
Cooling towers recirculate water against a flow of air, which cools down the water to be used for air-conditioning and other appliances. As the water travels through the appliances it heats up and warm wet air is expelled into the environment.
Legionella is common in most water environments; however, it doesn’t become a concern until it reaches large numbers. Where they thrive is in warm, aquatic environments and cooling towers, which operate at human body temperature, make an ideal incubator for these water-borne human pathogens.
6 Steps to controlling legionella in cooling towers
Poorly managed cooling towers, including neglect and insufficient maintenance, are among the major causes of legionnaires outbreaks.
Here is our 6-step system for the prevention, control and monitoring of legionella in cooling tower systems.
- Assess the hazards and prioritise the risks. Some of the significant threats include:
- Poor source water quality and water treatment failures
- Areas of stagnant water such as dead-legs
- Presence of biofilms on wet surfaces throughout the system which serve as a nutrient source for microorganisms
- Water temperature of 25 – 50 degrees Celsius
- Aerosol production
- Ease of cleaning and easy access for maintenance
- Identify ways to control the risks, for example
- Antimicrobial treatment for source water before it enters the cooling system
- Shorten or remove dead-legs wherever possible
- Filtration to reduce the potential of the system to form biofilms
- Implement control measures such as regular sampling and testing as per your state’s regulations and in conjunction with a water treatment specialist. Specialist chemicals are available, and can be formulated, for your specific cooling tower needs
- Develop procedures that include corrective actions for normal and incident conditions as well as the recording of any maintenance carried out
- Audit the systems and procedures every two years or as per your states Regulations.
- Support your staff with training and education
Most cooling towers likely to become contaminated
Most cooling towers are likely to become contaminated with Legionella at some point in their serviceable life. Therefore, it is vital to address the inherent risks if you want to avoid a meeting with the health department.
The overall benefit of quality water treatment chemicals for cooling towers is that they provide the means that allows the equipment to function optimally whilst using water efficiently. Their presence minimises microbial growth, scale and corrosion and is focussed on the prevention of Legionella outbreaks.
Chemology is an Australian owned manufacturer of water treatment chemicals with over 10 years of specialist knowledge and experience in the topic.
View our range of high quality Cooling Tower Treatments HERE