Ultraviolet (UV) is an electromagnetic radiation.
Disinfection using UV radiation is commonly used in wastewater treatment applications and is finding an increased usage in municipal drinking water treatment. Many bottlers of spring water use UV disinfection equipment to sterilize their water. Solar water disinfection has been researched for cheaply treating contaminated water using natural sunlight. The UV-A irradiation and increased water temperature kill organisms in the water
In an ultraviolet light system, water flows past ultraviolet lamps to expose microbes to energy at a germicidal wavelength of 253.7 nanometers. This exposure modifies the DNA in the cells of contaminants (bacteria, viruses, molds, algae, etc.) so that they can no longer reproduce, and thus present no threat to human health.
Ultraviolet (UV) Light; advantages
The principal advantages of ultraviolet light disinfection are that it does not use chemical feeds and does not produce toxic by-products. As a result, ultraviolet light systems do not need a dechlorination process and required safety measures are greatly reduced compared to alternative systems discusses.
An additional advantage is that it is more effective than chlorine in inactivating most viruses and requires a relatively short contact times to inactivate bacteria.
Ultraviolet (UV) Light; disadvantages
The primary disadvantage of UV light for potable water disinfection is that it does not provide a disinfecting residual.It is therefore not suitable for significantly sized drinking water distribution systems without the addition of a secondary disinfectant.
UV light is also ineffective against cysts and is not a great technology for disinfecting surface water sources.
Suspended and dissolved materials can impede the performance of ultraviolet light, and in these circumstances additional treatments are required to clear the water as it passes by the lights. As it provides no residual disinfectant and lacks an immediate measure of disinfection success (unlike chlorination systems), particular attention must also be paid to ensure that a lethal dose of ultraviolet light is being applied to organisms or re-infection of water can occur.
Source: Disinfection Technologies for Potable Water and Wastewater Treatment:
Prepared by: Leslie Snowden-Swan, John Piatt, Ann Lesperance - Pacific Northwest National Laboratory