UV Test

UV-Light

UV-light or better known as ultra violet light is electromagnetic radiation with a wavelength shorter than that of visible light but longer than soft X-rays.  The name comes from the Latin word ultra, which means beyond and violet being the color of the shortest wavelengths of visible light.  The first and second types of UV-light are alpha and beta and the third type, which is of interest to us for the purpose of cleaning water, is gamma rays or UV-C light.  Gamma rays are unique in their wavelength (<280 nm), which gives it germicidal capabilities. 

Ultraviolet lamps are used to sterilize tools, workspaces, medical and biological facilities.  The optimal wavelength of light is 254 nanometers, which is readily absorbed by DNA of living organisms.  These gamma rays are very harmful to the eyes and skin of humans and can cause cancer.  UV light at these germicidal wavelengths alters the DNA of microorganisms so that they cannot replicate.  These DNA altering wavelengths are produced by the sun but are mostly filtered out by the ozone layer of the atmosphere.  Without the ability to replicate the organisms will quickly die off because of the mutation in the DNA. 

Although UV-light is an effective way to treat water it is not recommended that this one process be used because some organisms can hide in cracks or simply get through unharmed.  The water could become recontaminated by not having proper water storage containers that are sterile or by the addition of dirty water to the clean water.  The water also must be at least 5 NTU or less in order for UV-light to work otherwise the water is to dirty to let all the light pass through.  This process requires power to run and a certain degree of training is required to ensure water safety.  Building an effective sterilizer is costly and needs constant monitoring as well as replacement at least once a year.