Article | Chemical treatment for legionella

Legionella bacteria often grow in lakes, ponds, and rivers and can cause Legionnaires’ disease. Outbreaks of Legionnaire’s disease originate from human exposure to water droplets from purpose-built HVAC systems (heating, ventilation and air conditioning). These units provide the optimum environmental conditions for the bacteria to thrive.


Chemical water treatments are highly recommended for any facility. In some cases, the law dictates that they are used to prevent cases of legionnaires’ disease – which can at times be fatal.

There are a number of factors to consider to help determine if your establishment would benefit from a chemical water treatment. You should be using chemical treatments if:

You have the responsibility of a high-risk establishment; these include:

    • Hotels
    • Restaurants
    • Schools
    • Public pools
    • Hospitals
    • Nursing homes
    • Your system stores or re-circulates water at temperatures above 20°C or below 60° The optimum temperature for legionella bacteria to thrive is between 20°C-45°C.
  • There are signs of scaling, sludge, grime or other fouling that provide a source of nutrients for bacteria to breed – even a small amount can be harmful to your health.
  • Your water systems have not been used recently – stagnant water offers the ideal breeding ground for bacteria to thrive in.

How do chemical treatments prevent Legionnaires’ disease?

Treatments often contain a combination of chemicals. Each chemical plays a part in preventing Legionella in water systems and the possible outbreak of legionnaires disease.

The following table describes the different types of water chemical treatments and how they work:

Legionella TreatmentEffects
Corrosion inhibitorsOrganic, inorganic and non-phosphate corrosion inhibitors are added to the water to prevent corrosion and limescale deposits which provide an excellent environment for the growth of the bacteria.
BiocideThis treatment kills the harmful microorganisms before they can grow and become a health threat.
DispersantThis treatment breaks down sludge and other dirt particles to penetrate and clean deposits.
OxidationOxidation treatments disinfect and deoxidise water systems to keep them clean and sanitary.

In any water supplement program, it is important that the treatment process is tailored to its particular use. Contact NCH Asia to find out more about our bespoke microbiological and chemical analytical services.

Most popular articles

Contact Us Today

NCH has been servicing various industries with maintenance. Find your industry for more information and products.

    nch contact
    Contact Us