As UV water treatment is a chemical-free process there is no need to handle potentially dangerous chemicals, such as chlorine, and no chemical disinfection by-products. Also, as UV disinfection is almost immediate, there's no need for contact tanks which are needed in chlorine disinfection.

Further benefits with UV disinfection include:

Lower equipment costs. No moving parts to wear out.
Low power consumption No change to the taste or odour of the water.
Simple maintenance with the appropriate pre-treatment.  

Disinfection is defined as “the act of disinfecting, using specialized cleansing techniques that destroy or prevent growth of organisms capable of infection.” Disinfection is considered a "4-log" reduction or equivalent to a 99.99% reduction. Log reduction is a measure of how thoroughly a decontamination process reduces the concentration of a contaminant.

In regards to water, there are typically two methods of water disinfection:
• Chemical disinfection: chlorine, ozone, iodine, bromine.
• Physical disinfection: UV light, boiling, fine filtration.

In chemical water disinfection a chemical must be added in order to destroy the microorganisms present. One of the most popular methods of chemical disinfection is chlorination, a common disinfection method for drinking water.

Using a chemical such as chlorine will not only target bacteria but it will also change the taste and smell of the water, the pH, and possibly form disinfection by-products (i.e. trihalomethanes).

Physical disinfection, including boiling, filtration and ultraviolet disinfection, does not require anything to be added to the water. One of the simplest and most effective ways to disinfect drinking water is by using UV disinfection.

  • When the contaminated water is boiled only the microorganisms are targeted killing them as the temperature increases.
  • When the contaminated water is fine filtered specific microorganisms are removed depending on their size and the rating of the filter.
  • When UV light sterilization is applied, only the microorganisms are targeted through DNA inactivation.

 

Using any of the above physical methods will not change the taste, odour or chemical makeup of the water.

UV disinfection is a relatively simple process.



Step 1: Pre-treated water enters the stainless steel chamber flowing around the UV lamp.

Step 2: The microbes in the water are exposed to the ultraviolet light (254nm wavelength) which alters their DNA, making them unable to replicate. The microbes are now harmless.

Step 3: The disinfected water leaves the chamber and enters your homes water supply. The water is now safe for drinking, bathing and safe for use in food production.

There are several barriers that can affect UV performance.

  • Suspended solids, both visible and non-visible, particulate matter, commonly referred to as turbidity.
  • Scaling caused by physical scale deposits on the quartz sleeve from iron, manganese or calcium carbonate.
  • UV absorbing compounds, most often caused by dissolved substances. Certain organic substances such as humic or fumic acids (tannins), and certain in-organic substances such as iron and manganese absorb UV light, reducing the chambers effectiveness. These contaminants must be addressed before entering the chamber for UV treatment to be effective. UV is not a stand-alone water treatment process and is always accompanied by other treatment processes.

Cutaway model of a UV disinfection reactor

Cutaway model of a UV disinfection reactor
(Credit: Z22 - Own work, CC BY-SA 4.0)

Example of a single-celled protozoa organism

Example of a single-celled protozoa microorganism

Once a UV water treatment system is chosen for the home, the question arises as to where to install the system.

If you only consume the water from one tap, the installation of a point-of-use (POU) UV system may be the best choice if only one tap exists in the dwelling.

A typical point-of-use installation

For homes that have more than one tap, including a bathroom faucet, the installation of a point-of-entry (POE) UV system will be the best choice for a whole-home water purification system.

With a POE install you have peace of mind that the water in your entire home has been treated. You may never drink from some taps in your home, but what if a guest happened to take a drink from a bathroom faucet, or perhaps you brush your teeth and use the water for that purpose? Safety and peace of mind is the main reason to install a whole home UV purification system.

A typical point-of-use installation