Typical UV disinfection systems involve the flow of water through a vessel containing a UV lamp as shown in Figure 1. As the water passes through this vessel, microorganisms are exposed to intense ultraviolet light energy which causes damage to genetic molecules (i.e. nucleic acids: DNA or RNA) needed for reproductive functions. This damage prevents the microorganism from multiplying or replicating in a human or animal host. Because the microorganism cannot multiply, no infection can occur. Disinfection of water is achieved when UV light causes microbial inactivation.
Figure 1 - Basic schematic of UV unit with bulb.
Ultraviolet (UV) light is electromagnetic radiation traveling in wavelengths in all directions from its emitting source (bulb). It is found in the spectral range of light between x-rays and visible light; UV light occurs with a wavelength ranging from 200 to 390 nanometers (nm). The most effective wavelength frequency, from the point-of-view of microbiological disinfection, is 254 nm as this is where the optimum energy intensity is found. This relationship between microbiological disinfection effectiveness and the wavelength frequency as emitted from the UV bulb is shown in Figure 2.
Figure 2 - % Effectiveness vs. Wavelength emitted from UV unit.