Ultraviolet
Ultraviolet light, at the germicidal wavelength of 253.7 nanometers, alters the genetic (DNA) material in cells so that bacteria, viruses, molds, algae and other microorganisms can no longer reproduce. The microorganisms are considered dead, and the risk of disease from them is eliminated. As the water flows past the UV lamps in UV disinfection systems, the microorganisms are exposed to a lethal dose of UV energy. UV dose is measured as the product of UV light intensity times the exposure time within the UV lamp array. Microbiologists have determined the effective dose of UV energy (expressed in microwatt- seconds/cm2) needed to destroy pathogens as well as indicator organisms found in wastewater.
Used properly, ultraviolet light effectively destroys bacteria, viruses and other microorganisms in water and wastewater, without using chemicals. By doing away with chemical treatment, many other problems are also eliminated. There is no longer any need to worry about operator safety or the requirement for buildings for storage and handling of dangerous solutions and gases. Costly liability insurance premiums are significantly reduced. Testing of effluent for chlorine residual is no longer necessary, and toxicity problems associated with chlorine use are eliminated.