Water Disinfection Methods

Learn about the different methods of water disinfection and which one is the most efficient.

Water disinfection is needed in many domestic hot and cold water systems to prevent hazardous Legionella bacteria from causing infection in end users.

There are a number of methods available today for water disinfection.

To find out which one is the most efficient, you can score each method on a series of different parameters, of which we will now look at these eight:

The ability to remove the biofilm.
The ability to kill bacteria in the biofilm.
The ability to kill free bacteria.  
The ability to disinfect water without leaving taste or smell in the water.
The life Cycle Cost of the method.  
The scalding risk of the method.
The method’s effectiveness towards bacteria in dead ends
And the method’s long term effect on bacteria and biofilm.

Notice how one of the most popular methods for water disinfection – thermal treatment – lacks two very important features:

The ability to remove biofilm and a long term effect.
In fact, the only method that scores on every parameter is the method where chlorine dioxide is used as a water disinfectant. We will now take a closer look at this method and show how it works in greater detail.

Chlorine dioxide consists of a mixture of sodium chlorite and hydrochloric acid. When the two components are mixed, an oxidizing disinfectant is formed along with the harmless by-products salt and water.

Chlorine dioxide has the ability to destroy the transport proteins in the legionella bacteria, and thereby kill the bacteria.

It also destroys all other living organisms in the water, such as viruses, fungi and algae.

Chlorine dioxide efficiently destroys biofilm in tanks and pipes as well.

In fact, scientists did a study of biofilm in silicone tubes and found that after six days of treatment with chlorine dioxide, the biofilm had been reduced to almost nothing. Chlorine dioxide is as gentle as it is efficient, because it requires much fewer chemicals than other biocides.

Chlorine dioxide is injected into the water system where the municipal water main enters the building. If you only want to treat the hot water, the injection point is here.

Now, let’s quickly recap the advantages of using chlorine dioxide for water disinfection:
- Chlorine dioxide removes biofilm, free bacteria and bacteria living in the biofilm.
- It has no effect on smell and taste.
- It is effective in dead ends.
- It has low cycle cost.
- It is not pH sensitive.
- It has long residual effect.
- and there is no scalding risk.

Course overview

Modules: 3
Completion time
Completion time: 9 minutes
Difficulty level
Difficulty level: Intermediate