Ultraviolet UV Water Purification And How It Works

May 9, 2016, by Ken Jorgustin


Apparently the most endorsed method of disinfection for home use in the United States currently is an ultraviolet light (UV) system.

It’s technically not a ‘filter’ (it doesn’t filter out anything by ‘capturing’ particulate contamination in a filter media) however a UV (Ultraviolet) system effectively accomplishes the end result by ‘zapping’ organic pathogens from the water supply with a ‘UV’ light source.

The method (science) even works by natural sunlight (albeit much slower) while newer technological advancements have enabled ‘near instant’ UV water disinfection systems that vary in size from handheld water bottles to whole-house systems.

Here’s more about how it works:

UV (ultraviolet) light ‘inactivates’ pathogenic micro-organisms by disrupting their DNA (the DNA of the microorganisms is deactivated which makes them unable to reproduce). In fact, the method has been around for many years and is being used around the world in ‘developing countries’ for water purification – called ‘SODIS’ (Solar Water Disinfection).

The SODIS method is recommended by the WHO, UNICEF, and the Red Cross, and all it requires is sunlight and PET bottles (glass doesn’t work as well). How does it work? Clear PET bottles are filled with the water and set out in the sun for 6 hours. The UV-A rays in sunlight kill germs (e.g. viruses, bacteria, parasites, giardia, cryptosporidia).

SODIS taken to the next level…
The same principle is now being applied via ‘high-tech’ whereby ultraviolet (UV) lamps are utilized to nearly instantly achieve the same results of water disinfection. UV lamps are designed to emit UV-C or “germicidal UV” radiation of much greater intensity than sunlight.

Geek alert: Almost all of a UV lamp’s output is concentrated in the 254 nanometers (nm) region in order to take full advantage of the germicidal properties of this wavelength.

These UV lamps are made in varying sizes to fit with small water bottles such as the following…
Camelbak UV Water Purifier

…or even whole-house UV water systems such as this one from the world’s largest supplier of residential and light commercial UV water disinfection systems:
VIQUA Home UltraViolet Water Disinfection System

Other types of water purification systems use chemicals or very fine screens to clean water. While these methods are effective, bacteria can become immune to chemicals and viruses can slip through all but the finest screens. Apparently no known bacteria or viruses are immune to ultraviolet light.

Note: If your water is turbid (cloudy), then UV disinfection is inhibited (cloudiness from solids in the water may protect the bacteria and viruses from the ultraviolet light).

Note: Consider installing a sediment filter (5 microns or less) ‘upstream’ from the UV system.

Note: If your water hardness over 7 grains, you should install a water softening device in front of your unit. Hard water will eventually leave a calcium/magnesium film which may reduce or block the UV rays.

I posted this out of interest – having recently researched the technology since I’m looking to install a whole-house UV water purification system simply as a precaution for my shallow well (a natural spring) given the potential for surface contamination issues during heavy-rain runoff, etc.. (and I’m a bit of a stickler for clean water 😉 ).

I’m curious if any of you have experience in UV water ‘filter’ products or whole-house systems…