How to prepare your cooling tower to avoid legionellosis with the arrival of spring?


What is Legionellosis or Legionnaires’ disease?

It is a severe form of pneumonia – lung inflammation usually caused by infection. The bacteria that cause this disease is known as legionella, typically found in water sources.

Several cases of Legionnaires’ disease strike Québec every year. All buildings with cooling towers must implement strict procedures to limit legionella contamination.

This article highlights a few tips for reducing the risk of legionella contamination and how to implement sustainable solutions.

A few facts about legionellosis:

Without proper treatment, the water in cooling towers can cause serious issues. Today, cooling towers are closely regulated and monitored by the Québec government. This is to avoid another outbreak of Legionnaires’ disease, like the one in 2012 and more recently those that occurred in the Montréal area during the summer of 2021 and 2022.

Legionnaires’ disease spreads when there is water stagnation in cooling tower piping and in water tower basins that do not generate a constant flow. Other factors likely to trigger it are poor temperature control, organic and mineral deposits such as scale, abundant biofilm, metal residues and protozoa, as well as lack of equipment maintenance leading to corrosion and scaling. Please note that, according to Building Law B-1.1, a Legionella concentration of over 1 million results in an automatic shutdown of your water tower.

The management and control of Legionella proliferation is therefore essential to control the risk of exposure and minimize the dispersion of contaminated droplets and aerosols.

How to maintain your water tower?

A proper maintenance program for your cooling towers should include the following:

  • Procedure for winterizing and restarting, if applicable, and the related treatment to limit the risk of bacteria
  • Shutdown and restart procedure during operation
  • Cleaning procedure

Additionally, you will need a procedure for maintaining water quality. This should include an assessment for characterizing the water in your tower. This assessment will enable you to establish a treatment plan specific to your system, considering that the source of your water can have a significant influence on your water quality maintenance program.

The treatment plan will consider, among other things, the water recirculation rate and fresh water supply, the level of suspended matter, aerosol dispersion limitation, seasonality and the level of performance you need to maintain your water tower systems. These parameters will have an impact on the nature and frequency of treatments required to maintain your water, maintain the integrity of your system, and reduce corrosion and scaling.

A water analysis plan needs to be set up to control water quality and monitor the performance of your treatment plan. The latter should make it possible to limit bacterial growth and to keep Legionella pneumophila levels below 10,000 CFU/L at all times, in order to comply with regulatory requirements.

In addition, maintenance of mechanical components, in accordance with the manufacturer’s recommendations, will be necessary to ensure that your equipment operates safely. 

Need a helping hand? 

Worried about Legionnaires’ disease? Want to talk to a cooling tower solutions expert? If you have any questions, please contact us at 514 422-0444.