Legionella Risk Factor: Disinfectants

The level of disinfectant in your water is a risk factor for Legionella. Chemicals, such as chlorine and monochloramine, are common methods of controlling Legionella and low levels can raise the risk of Legionella growth.

Most experts agree that disinfectants are needed to control pathogens. To get an idea of recommended disinfectant levels, see our Chemical Demand Calculator for Legionella.

You will also find it helpful to learn about Legionella secondary disinfection and the difference between supplemental disinfection and secondary disinfection for waterborne pathogens including Legionella.

Below are common oxidizing chemical secondary disinfection systems:

• Chlorination
• Monochloramines
• Chlorine Dioxide
• Mixed Oxidant Solution (MOS)
• Ozonation
• Advanced Oxidation Process (AOP)

In addition, here is the a common non-oxidizing chemical secondary disinfection system:

• Copper-Silver Ionization

Disinfectant levels are directly affected by the other risk factors such as:

• Water age
• Stagnant water (has older disinfectant that will cause its effectiveness to diminish)
• Old plumbing designs (can introduce many challenges including oversized pipes and stagnant water)

All factors need to be considered to determine the correct levels, as well as monitoring levels over time. All of these factors can be taken into account with a Legionella control and defensible water management program.

Disinfectants and Biofilm

If your building has an elevated risk of biofilm, it’s important that the correct type of disinfectant is used. Even if you’re using the correct levels of disinfectant and you have biofilm, you will not be effectively preventing Legionella since biofilm is where 90% of Legionella and other pathogens grow. Chlorine, for example, doesn’t affect or decrease the level of biofilm. Mixed oxidants solution (MOS) and chlorine dioxide systems for Legionella control are much more effective at removing biofilm and preventing it from forming. Also see how different disinfectants compare and the effects of filtration on disinfectant efficacy.

Legionella Control Systems and Water Management Plans

Do you want to keep your customers, patients, and employees safe? Contact Legionella Control Systems at info@legionellacontrolsystems.com or 888-416-8626. Our experienced engineering team is ready to help.

See all of the Legionella risk factors: Water Age (stagnant water), Temperature, Disinfectant Levels, and Scale/Sediment.

Contact Legionella Control Systems for CDC Legionella risk assessment and Legionella testing.