The UV treatment is a physical process used in water and wastewater treatment for disinfection, oxidation and removal of organic compounds. In contrast to chemical processes such as chlorination or ozonation, UV treatment is purely physical and leaves no chemical residues. It is therefore particularly environmentally friendly and is used in drinking water treatment, process water treatment, wastewater treatment and for the reduction of TOC (Total Organic Carbon).

By using high-energy UV radiation, microorganisms can be inactivated, organic compounds oxidized and stubborn pollutants such as pharmaceuticals, pesticides and residual chemicals broken down. Advanced processes such as UV oxidation play a central role, especially in the reduction of difficult-to-degrade contaminants in water.

Basics of UV radiation

The effect of UV treatment is based on ultraviolet radiation, an energy-rich part of the electromagnetic spectrum with wavelengths between 100 and 400 nanometers (nm). UV radiation is divided into three categories:

1. UV-A (315-400 nm): Acts mainly on organic molecules, but with low energy density.
2. UV-B (280-315 nm): Medium energy density, harmful to living cells.
3. UV-C (100-280 nm): Highest energy density, used for water treatment as it effectively inactivates microorganisms and breaks chemical bonds.

UV-C radiation is primarily used in water and wastewater technology, particularly at a wavelength of 254 nm, as this is optimal for the DNA inactivation of microorganisms and the oxidation of organic substances.

Technical applications of UV treatment

1. UV disinfection

UV disinfection is one of the most common applications of UV treatment and is used to inactivate microorganisms such as bacteria, viruses, protozoa and fungi.

• Mechanism of action:

  • UV-C radiation destroys the DNA/RNA structures of microorganisms by forming thymine dimers. This prevents the microorganisms from dividing and multiplying.
  • Unlike chemical disinfectants, UV treatment does not leave behind any by-products such as chloramines or organic halogen compounds.

• Areas of application:

  • Drinking water treatment: Ensuring hygienic water quality.
  • Process water treatment: germ reduction in the pharmaceutical and food industries.
  • Cooling water systems: Prevention of microbial contamination and biofouling.

2. UV oxidation (Advanced Oxidation Processes, AOPs)

UV oxidation combines UV radiation with chemical oxidants such as hydrogen peroxide (H₂O₂) or ozone (O₃) to generate hydroxyl radicals (-OH), which are highly reactive and capable of oxidizing difficult-to-degrade pollutants.

• Principle of action:

  • UV radiation splits H₂O₂ or O₃ into hydroxyl radicals.

  • These radicals attack organic molecules and break them down into smaller, less toxic compounds such as carbon dioxide (CO₂) and water (H₂O).

• Application:

  • Removal of micropollutants such as pesticides, pharmaceuticals and endocrine disruptors.
  • Elimination of micropollutants and poorly degradable substances.
  • Odor removal and color removal from water streams.