Ultraviolet Radiation

Ultraviolet (UV) light is found in sunlight and is within the electromagnetic spectrum. The range between 200 to 300 ηm is known to be germicidal (lethal to microorganism).

By disrupting the reproductive mechanism (DNA) of bacteria, viruses, yeasts or mold, the organisms are inactivated and thereby eliminated as agents of disease and biological growth.

An UV system typically consists of a lamp that is encapsulated by a quartz sleeve. This lamp is situated concentrically in a tubular chamber with the liquid to be treated forming an annular cylindrical flow pattern around the lamp, which emits the UV radiation on a 360° pattern. The efficiency of the treatment is a function of the lamps power related to the mass of water flowing by it. The efficiency also is a function of the clarity of the liquid which determines the effective penetration depth of the UV rays.

The advantage of UV radiation is that it is an effective method to destroy microorganisms in a continuous and safe manner at acceptable capital cost and low energy usage. However, the life of a UV lamp is limited and the use of it is restricted to very clear water, even if the lamp sleeve should be equipped with a wiper mechanism that removes fouling, which may block UV light emitted from the UV lamp. Also, UV light will eliminate microorganisms only.

For these reasons, UV radiation will seldom be found as a standalone water purification device, but it is widely used as a post treatment step for filtration based or evaporative purification methods that produce very clear water.