What is the effective wavelength of UV lights in nanometers?

The effective wavelength of UV lights commonly used in disinfection processes, specifically in water treatment systems such as those found in Fresenius Water Systems, is 254 nanometers. This wavelength is particularly effective for inactivating microorganisms, including bacteria and viruses, because it corresponds to the peak absorption of UV light by the DNA and RNA of these pathogens. When UV light at this wavelength is absorbed, it causes damage to the genetic material, preventing the microorganisms from replicating and effectively rendering them harmless.

While other wavelengths, such as those listed in the options, exist, they are not as effective for microbial inactivation as the 254 nanometers. UV light at this wavelength is typically generated by low-pressure mercury vapor lamps, which are standard in water treatment applications.