UV-C disinfection of water

UV-C water disinfection technology consists of a physical treatment without disinfectant chemicals. Moreover, its effectiveness on micro-organisms makes it particularly interesting.

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UV Light – Definition

Ultraviolet or “UV” is a type of energy that is found in the electromagnetic spectrum. That is, between X-rays and visible light. This means that UV rays are not perceptible to the human eye. However, we are exposed to this every time we go out in the sun. In fact, UV light is responsible for sunburn.

Their wavelength is between 100 nm and 400 nm. These rays are divided into three categories, each of which is increasingly energetic: UV-A (315 – 400 nm), UV-B (280 – 315 nm), UV-C (100 – 280 nm)

For disinfection, we are only interested in UVC.

Principle of disinfection by UV radiation

UV-C water disinfection systems use special lamps that emit UVC light. These have a particular wavelength capable of disrupting the DNA of microorganisms.

These UV light waves are also called “spectrum” or “germicidal frequency”.

The frequency used in killing microorganisms is 254 nanometers (nm).

When water passes through a U-V water treatment system:

  • the rays produced by the lamps reach the pathogenic microorganisms that pass by. These UV lamps contained in a reactor are usually made of stainless steel.
  • They are then exposed to a lethal dose of UVC light that attacks the DNA, eliminating the microorganism’s ability to reproduce.
  • Thanks to this process, it cannot replicate itself or infect other organisms with which it comes into contact.

This process of exposing water to UV light is simple and effective, destroying 99.99% of harmful microorganisms without adding chemicals to the water. In addition, it is a safe method that creates no harmful chemical by-products.

 
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How to eliminate bacteria

To effectively eliminate bacteria in the water, ultraviolet type C (UV-C) disinfection is a proven and environmentally friendly method. This physical process, without the addition of chemicals, neutralizes microorganisms by altering their DNA, making them unable to reproduce and therefore harmless.

Working principle of UV-C disinfection

UV-C disinfection systems use special lamps that emit light at a wavelength of 254 nanometers, which is optimal for the germicidal effect. When water circulates near these lamps, the microorganisms in it are exposed to this light, which disrupts their DNA and prevents their reproduction. This process eliminates up to 99.99% of pathogens without changing the physicochemical properties of the water, such as taste or odor.

Components of a UV-C Disinfection System

A typical system includes :

  • Reactor : A chamber where water is exposed to UV light.

  • UV lamp : Source of UV-C radiation.

  • Quartz sleeve : Tube protecting the lamp while allowing UV light to pass through.

  • Ballast: Control unit that regulates the power supply to the lamp.

These components work together to ensure optimal water disinfection.

Applications of UV-C disinfection

UV-C disinfection is used in a variety of areas, including:

  • Domestic consumption : Drinking water treatment for homes and cottages.

  • Industries : Pharmaceutical, food processing, cosmetics, etc., requiring water free of microorganisms.

  • Pools and spas : Maintaining water quality without excessive use of chemicals.

  • Aquaculture : Protection of aquatic farms against pathogens.

This versatility makes UV-C disinfection a preferred solution to ensure safe and healthy water in many applications.

FAQ

Can you use a UV system with untreated rainwater or borehole?

Yes, but it is essential to pre-treat the water before UV disinfection. Rainwater or borehole water may contain particles, iron, manganese, or organic matter that reduce the effectiveness of UV rays by blocking the rays. Mechanical pre-filtering (cartridge, sand filter, etc.) and possibly activated carbon treatment or a softener are often necessary. A water test is strongly recommended prior to installation.

The lifespan of a UV lamp typically ranges from 8,000 to 12,000 hours, or about 1 year of continuous use. Some units have a replacement hour meter or alarm. Even though the lamp continues to emit visible light, its germicidal power decreases over time, making disinfection ineffective if it is not replaced.

The UV dose corresponds to the amount of UV energy received by the water as a function of the exposure time and the intensity of the radiation. It is measured in millijoules per square centimetre (mJ/cm²). For effective disinfection, a minimum dose of 30 to 40 mJ/cm² is often necessary. If the water flow is too high or the water is cloudy, the dose may be insufficient. Hence the importance of choosing a well-sized device.

Absolutely. UV disinfection is often integrated into multi-stage treatment chains: mechanical filtration, activated carbon, softening, or even reverse osmosis. This combined approach makes it possible to meet complex needs, for example for well water loaded with nitrates or pesticides, or to guarantee complete potability. The UV sterilizer usually comes as a last step, to ensure bacteriologically safe water.

UV systems do not use any chemicals, which prevents the formation of potentially harmful by-products such as chloramines or trihalomethanes. Unlike chlorine, UV rays leave no residue in the water and do not alter the taste or smell. This makes them more environmentally friendly and safer for sensitive users (allergies, asthma, etc.). In addition, some recent models are equipped with energy regulation technologies, reducing power consumption.

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