September 20, 2019
What is Ultraviolet Water Purification?
Ultraviolet water purification (UV) is a highly effective process of purifying water by applying a light of specific intensity and wavelength that kills or inactivates pathogens such as bacteria, protozoa, viruses and other minuscule life forms. It does not necessarily kill them, but damages them enough to not allow reproduction.
If a flow of water is purified using a UV light, any pathogen that was once inside will no longer be able to spread. Today, it is one of the most efficient ways of removing harmful bacteria and protozoa such as e.coli and giardia from a high flow of water.
What are the benefits of Ultraviolet Water Purification?
- A high flow of water (several thousands of litres per hour) can be processed (unlike most Reverse Osmosis or Ultrafiltration systems)
- Very cost-effective
- No cleaning required & easy to maintain - the light bulb only needs to be changed once a year
- Inactivates all pathogens such as bacteria, protozoa & other living organisms
- Every drop of water is purified, no water wastage
How do you install an Ultraviolet Water Purification System?
Ultraviolet light can cause severe damage to humans eyes and skin, so UV lights are generally enclosed in a stainless steel casing to block any light from escaping, while the water inside the casing flows around the light bulb. It is typically installed as a last stage of a water purification system: the water needs to be completely cleared of any sediments or particles for UV light purification to be effective. If you process turbid water through a UV light, the turbidity creates shadows that might protect some pathogens from exposure to the UV light.
The typical set up would be a 2 or 3 stage Big Blue water filtration system with sediment filters of 5, 10 or 20 micron; a carbon filter to absorb any chlorine; and thereafter a UV cartridge to process the water and inactivate any remaining pathogen.
Pro tip: A UV light bulb needs some time to warm up. The light bulb needs to reach a certain temperature to emit the exact wavelengths at the right intensity that will be harmful to the bacteria and protozoa. The UV system should not be switched on and off. It must be left permanently on, 24/7.
What are the costs of Ultraviolet Water Purification Systems?
For an entire house, we usually recommend a 55/65W UV water purification system, which typically costs between R2500 and R4000 at retail price in South Africa. The higher end units with alarm systems may cost between R4000 and R5000.
A 3 stage Big Blue water filter system with a 55 UV light retails between R7000 and R8000. If a lower flow of water is required, there are more cost-effective systems with a lower wattage.
Prices are from 2019, in South Africa.
How do you maintain an Ultraviolet Water Purification System?
The UV light bulb only needs to be changed once a year and no cleaning is required as it is not a filter. The ballast needs minimal maintenance. Most of them have an LED light bulb - if it is ON or green it is fine, if it red or OFF then there is a problem.
Make sure that the water going into the UV stage has very low turbidity and is free from all sediments. A sediment filter can be used beforehand to remove dirt and debris from the water.
Are Ultraviolet Water Purification Systems recommended when purifying water?
For any drinking purposes, a UV system is highly recommended as it is very efficient in eliminating any water-born pathogens such as giardia and e.coli: those pathogens are unfortunately very common in areas of South Africa where sewage water processing is insufficient. For the price, a UV purifier can also handle a high flow of water.
One limitation is that it cannot handle metals or chemical pollutants (pesticides etc). A KDF filter or a Reverse Osmosis system would be required for this..
Recommended Ultraviolet Water Purification Systems
Big Blue Water Filtration System With Advanced 65W Germicidal UV Sterilizer