How does a UV disinfection system work? 

A UV disinfection system uses ultraviolet (UV) radiation to kill bacteria, viruses, and other microorganisms that may be in your water supply. A UV system can be used in combination with other water treatment technologies such as filtration, chlorination, or reverse osmosis to achieve disinfection goals. 

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The effectiveness of a UV system depends on several factors, including the wavelength and intensity of the UV radiation, the ability of the microorganisms to resist the UV, the duration of exposure, and the presence of particles that can shield the microorganisms from the UV. The effectiveness of a UV system can also be affected by other conditions, such as water quality, the presence of airborne particles, and turbidity. 

Viruses and other pathogens often are exposed to UV radiation via surface-encapsulated forms, such as extracellular “viral biofilms.” These structures protect microorganisms from the irradiance of the UV source and enable the organisms to remain viable even after being irradiated. This phenomenon, known as reactivation, is an important factor in the efficacy of UV systems for disinfecting contaminated surfaces. 

UV light is a type of electromagnetic energy that is produced by low-pressure mercury lamps and other devices. The germicidal properties of UV radiation are primarily due to its ability to destroy DNA and nucleic acid. In addition, it breaks chemical bonds in some materials and can damage insulating materials and gaskets. 

Some UV systems use UV LEDs, which emit a narrow band of radiation in the 260-nm range. They are becoming increasingly popular because they produce minimal amounts of harmful emissions and are more efficient than low-pressure mercury lamps in many applications. 

Most UV systems use a quartz sleeve that encases the UV lamp and is designed to keep it at an ideal temperature of about 104 deg F. The sleeve is typically surrounded by an electrically powered flow control device that prevents the water from flowing past the bulb too quickly, assuring appropriate contact time between the irradiating UV lamp and the water. 

Other types of UV systems have a bulb positioned in the water, with the lamp’s light source directly in the water flow. These systems have been found to be more effective than those that encase the lamp in a quartz sleeve because they allow the bulb to be placed more closely to the water flow, assuring direct and complete irradiation of the microorganisms. 

Because of the high cost of germicidal bulbs, some systems rely on a combination of UV lights, such as LEDs and lamps that produce a wider wavelength range. These combinations are more expensive than single-source systems that use a single bulb, but they can provide more consistent disinfection rates and lower maintenance costs. 

Regardless of the type of disinfection system, water that contains high levels of minerals such as calcium or magnesium can coat the sleeve and reduce treatment efficiency. This is why pretreatment with a water softener or phosphate injection system may be necessary to minimize mineral build-up on the sleeve and improve UV disinfection performance.