UV water filtration, or more precisely water disinfection using UV rays, is based on subjecting it to electromagnetic waves. UV rays are rays with a length ranging from 100 to 400 nm, meaning they are a type of light located between visible light and X-rays.
UV light, or simply ultraviolet, has specific properties, which we'll explain in a moment. To produce it, highly technologically specialized sterilizers with emitters containing mercury vapors are needed.
Due to their operation, the entire setup must be tightly enclosed in a steel reaction chamber into which the water we want to disinfect is introduced.
The technology of water desinfection using UV or UV-C rays is not new - it's developped since XIX century. To get more info about the history of the UV Light and this technology - check our another article.
The entire mechanism of water disinfection using UV is based on the fact that UV rays eliminate strains of bacteria, as well as viruses, mites, fungi, and parasites living in water. However, the process of bacterial elimination occurs only when the water is directly exposed to UV radiation - that is, it does not last longer than the water disinfection process itself (we mean exposure to UV rays emitted by lamps). This is a very important piece of information, indicating that by drinking water subjected to previous treatment, we can be certain that the UV radiation process is completed.
In the case of a UV water sterilizer, this process occurs only in the so-called reaction chamber, inside the device.
✅ Water cannot absorb UV rays, and after flowing out of the sterilizer, it is not only free from bacteria, algae, fungi, viruses - but it also does not retain the UV rays to which it was previously exposed. Therefore, it can be safely used without concern for the direct impact of UV radiation on human or animal health. Water purification using ultraviolet rays is therefore not harmful to humans, provided they are not directly exposed to UV radiation (specifically, irradiation). For this reason, the UV lamp mechanism can only be activated when it is located in the reaction chamber, inside the sterilizer. Filtration of water using UV is not dangerous - but exposure of the skin and eyes to UV rays is highly discouraged, or at least strongly advised against.
UV rays do not affect the physicochemical characteristics of the filtered water, such as pH or composition. Like any light, they may slightly affect the water temperature, but only if subjected to prolonged filtration (UV rays are not capable of boiling water even if the irradiation process lasts very long).
✅ The only change is the removal of unwanted microorganisms from the water, which in our conditions often boils down to bacteria such as E. coli or coliform bacteria. Water treatment involves their biological elimination, which often leads to the disappearance of unpleasant odors or discoloration - but apart from that, the composition of the filtered water remains unchanged.
It's important to remember that effective water disinfection requires selecting the appropriate dose of UV radiation. Too small a dose will only improve the situation partially. Fortunately, as repeatedly proven, UV radiation for water disinfection cannot be overdosed, so selecting an excessively large UV sterilizer cannot cause health damage.
The image shows a view of E. coli bacteria, commonly known as colon bacillus - a prevalent problem in Europe, mainly affecting water from private sources, such as private wells. It occurs less frequently in water supply networks, which are subject to certain preventive requirements. E. coli is the main reason for water treatment noted by sellers of UV systems.
If used for water filtration, UV rays cannot be harmful. However, it's important to avoid exposing the skin and eyes to their direct effects, which can only occur if the lamp is activated outside of the sterilizer (i.e., outside the reaction chamber). Direct UV exposure eliminates live microorganisms and similarly affects skin tissue negatively. Prolonged UV exposure to the skin can be carcinogenic. Long-term exposure of the eyes to UV radiation has been associated with a higher frequency of cataracts.
Therefore, it's important to use sterilizers in accordance with their intended purpose and the manufacturer's recommendations. When used properly, they are safe and positively impact health. Under no circumstances should children operate electrical water treatment devices.
Before we delve into the drawbacks of home water purification, let's clarify the terminology. Technically, we should refer to it as water disinfection with UV or UV-C radiation. It's not water filtration in the traditional sense. It's not a filter that removes mechanical particles, but rather it eliminates what's most dangerous, which are microorganisms. That's why it's recommended to install solid particle filters before sterilizers (which is actually done before most devices installed directly in the hydraulic system). Only then can we talk about a properly functioning filtration system.
✅ In essence, water purification with UV-C radiation has few drawbacks, although it doesn't solve all problems, and a proper solid particle filter is still needed for complete water treatment. UV lamps also have their requirements regarding the water they treat - namely, they don't like water with high iron content, which tends to gel. Although it's hard to consider this a flaw in home water purification systems - excessively high iron content in water can damage any device or hydraulic system.
Certainly, some people may consider the price of a UV water filter a drawback - the cost of a decent stainless steel sterilizer capable of serving a single-family home starts from 160 to 250 €. However, this is a one-time cost, and the ongoing cost of using such a lamp is only 10-20 € per month (the cost of electricity consumption) plus the cost of replacing the bulb approximately once a year (around 16-30 €).
The cost of a UV water filter for some specific application with much lower flowrate of water is not so expensive - it can costs from 50 to 150 €.
The most expensive are bigger industrial UV water purifiers for large buildings, big hotels or commercial swimming pools. Some examples you can find below.
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