Ultraviolet (UV) light is invisible radiation within a range of the solar spectrum. UV is similar to the wavelengths that are produced by visible light, but much shorter. UV radiation is measured in millionths of a millimeter, i.e., Angstrom units (one Angstrom unit wave-length equals one hundred-millionth of a centimeter), and like visible light, it primarily has a surface effect.
Ultraviolet lamp radiation of 2537-Angstrom units (or 254 nanometers) wavelength must hit the microorganism to inactivate it, and each microorganism must absorb a specific amount of energy to be destroyed.
Proteins and nucleic acid, which all microorganisms contain as their main constituents, absorb UV radiation energy. After absorption, the UV energy destroys or inactivates the DNA (deoxyribonucleic acid), thus preventing the microorganisms from reproducing.
Sterilization of water implies that all life, i.e., bacteria, mold, virus, algae, and protozoa, are destroyed. Table I gives the absolute amount of UV necessary to kill many of the common types. Our systems can also supply an 1849A (185NM) ultraviolet lamp that produces ozone (03) disinfection residuals, and in most cases this lamp interchanges with our standard 2537A ultraviolet lamp.
Complete sterilization is not necessary for the production of potable water. However, the water must conform to the drinking water standards of the EPA or those of the agency governing your supply. Normally, the water must contain less than 2.2 coliforms per 100 ml to be considered safe to drink. The coliform groups of microorganisms are generally associated with fecal matter and indicate that pathogenic (disease-causing) organisms, such as typhoid, may be present.
Tags:microorganisms , radiation , ultraviolet , water