What is Ultraviolet Disinfection and how does it work?
Ultraviolet Disinfection is a means of killing or rendering harmless microorganisms in a dedicated environment. These microorganisms can range from bacteria and viruses to algae and protozoa. UV disinfection is used in air and water purification, sewage treatment, protection of food and beverages and other disinfection and sterilization applications. A major advantage of UV treatment is, UV disinfection is capable of disinfecting water faster than chlorine without cumbersome retention tanks and harmful chemical disinfectants.
Ideally homeowners with wells will have water that is free from organisms. However, having a water treatment system for microorganisms adds an extra level of security.
UV radiation works as a drinking water disinfectant by altering the cellular material (DNA) in most microorganisms (viruses, bacteria, and protozoa) so that they cannot reproduce and cause infection.
UV treatment systems produce light radiation over a narrow range of wavelengths known to "zap" most types of microorganisms.
UV systems may use "low-pressure" or "medium=pressure" mercury vapor lamps. In order to kill microorganisms the water must be exposed long enough for the UV light to do its work. For this reason UV treatment is an appropriate technology for residences because most home water needs are only for flow rates of a few gallons per minute.
An advantage of UV systems over chlorination is that no chemicals are added to the water and UV treatment does not cause the formation of any known toxic byproducts.
However, UV treatment provides no residual germicidal protection. it is important the UV system function within the manufacturer's design specifications to maintain the proper UV irradiation dose will ensure that microorganisms are fully irradiated (inactivated).
A UV water treatment system is relatively simple in design. Source water flows into a closed chamber with a UV lamp in the center of the chamber. The flow rate through the chamber must allow all the water to be exposed to the UV light. High turbidity in water can block light or hide microbes. Dissolved substances such as iron, manganese, organic carbon, and nitrates will increase the absorbance of the UV radiation by the source water, thus reducing the delivered UV dose. Pretreatment to reduce the concentration of these compounds may be necessary to optimize the performance of the UV system.
It is essential that any water treatment system designed to protect against microorganisms is properly installed and maintained. UV systems are generally trouble free and low maintenance, but they need to be checked and serviced. To be confident, a "fail-safe" system can be installed so that if the UV system stops operating the water system shuts off.