Why are two different wavelengths used in water treatment?
Two different UV wavelengths are employed in water treatment 254 and 185 nm. 254 nm UV light is called the germicidal light because of its ability to destroy microorganisms. It is used to disinfect and to destroy ozone. It penetrates the outer cell wall of the microorganism, passes through the cell body, reaches the DNA and alters the genetic material, destroying the organism. The 185 nm light carries more energy than the 254 nm light. It generates hydroxyl (OH·) free radicals by cleavage of the water molecules, and is used in TOC reduction to decompose organic molecules into carbon dioxide and water.
