UV radiation is invisble to the human eye but its affects can be observed through the fading of coloured clothes and plastics when left out in the sun, as well as causing damage to our skin. The UV radiation present in sunlight can break down the chemical bonds causing the colour to fade or skin to become burnt. 


Similarly the light emitted by UV sterilisation units with a wavelength of 254 nm irradiates bacteria, viruses, algae and protozoa cell DNA structures. The UV light penetrates through the cell wall and cytoplasmic membranes which re-arranges the DNA and destroys the nucleic acids, rendering them unable to perform vital cellular functions. UV sterilisation does not remove cells from the water stream but it kills them and prevents further growth or multiplication. 


Most UV systems consist of UV lamps submerged in storage tanks or held inside polished housings with the water flow passing around the UV lamps.