Ultraviolet water purification lamps produce UV-C or "germicidal UV", radiation of much greater intensity than sunlight. Almost all of a UV lamp's output is concentrated in the 254 nanometers (nm) region in order to take full advantage of the germicidal properties of this wavelength. Most ultraviolet purification systems are combined with various forms of filtration, as UV light is only capable of killing microorganisms such as bacteria, viruses, molds, algae, yeast, and oocysts like cryptosporidium and giardia. UV light generally has no impact on chlorine, VOCs, heavy metals, and other chemical contaminants. Nevertheless, it is probably the most cost effective and efficient technology available to homeowners to eliminate a wide range of biological contaminants from their water supply. Recent testing has also shown that UV can be effective at destroying certain VOC's, although we would not specifically recommend the technology for VOC reduction.
UV water treatment offers many advantages over other forms of water treatment for microbiological contaminants. Most importantly, it does not introduce any chemicals to the water, it produces no bi-products, and it does not alter the taste, pH, or other properties of the water. Accordingly, in addition to producing safe drinking water, it is not harmful to your plumbing and septic system. Furthermore, it is easy and cost-effective to install and maintain without any special training.
Trojan Technologies, manufacturer of the Viqua (Trojan) UVMax line of household ultraviolet sterilizers, and R-can, which makes the popular Sterilight brand of UV sterilizers, are pioneers and world leaders in the field of UV water treatment. These companies even manufacturer large UV sterilization systems that can be used by municipalities and regional water districts for large-scale water disinfection.
How UV WorksUltraviolet purification uses a UV light source (lamp) which is enclosed in a protective transparent sleeve (usually quartz). The lamp is mounted such that water passing through a flow chamber is exposed to the UV-C light rays. When harmful microbes are exposed to the UV rays, their nucleic acid absorbs the UV energy, which then scrambles the DNA structure of the organism. The cell is rendered sterile and can no longer reproduce. The cell is now considered dead and is no longer a threat.
ApplicationsUV treatment is an excellent choice to eliminate biological contamination from most home drinking water, whether your home is on a municipal water system or untreated private system (well, lake water, etc.). Its sole purpose is to kill harmful biological contaminants, and therefore should always be combined with other forms of filtration (GAC / carbon block, KDF, or reverse osmosis) for reduction of heavy metals, chlorine, VOC's, and other chemical contaminants.
What Contaminants Does UV Remove?There are no micro-organisms known to be resistant to UV, unlike chlorination. UV is known to be highly effective against bacteria, viruses, algae, molds and yeasts, and disease causing oocysts like cryptosporidium and giardia. In practice, bacteria and viruses are the cause of most major waterborne pathogenic diseases. Of these enteric viruses, hepatitis virus and Legionella pneumophila have been shown to survive for considerable periods in the presence of chlorine, but are readily eliminated by UV treatment. For most microorganisms, the removal efficiency of UV for microbiological contaminants such as bacteria and viruses generally exceeds 99.99%. Specifically, the following are moved to an efficiency of greater than 99.99%: E-coli, Salmonella typhi (Typhoid fever), Salmonella enteritidis (Gastroenteritis), Vibrio cholerae (Cholera), Mycobacterium tuberculosis (Tuberculosis), Legionella pneumophila (Legionnaires' Disease), Influenza Virus, Polio Virus, and Hepatitis A Virus (better than 90%). Countertop UV systems are generally not recommended for removing oocysts such as giardia and cryptosporidium unless equipped with a 0.5 micron carbon block pre-filter since the exposure time the contaminant has to the UV ray is not always long enough to provide an adequate UV dose for disinfection of these more complex organisms. Whole house UV systems like the Trojan UV Max on the other hand, are capable or killing waterborne oocysts at household flow rates when a properly sized model is selected for the application.
Arsenic BacteriaWhole-House UV Systems
Point-of-Use UV Systems
Commercial UV Systems
Typical Maintenance RequirementsUV lamps (bulbs) require annual replacement to ensure optimal performance. UV lamp performance, just like any other light source, will slowly diminish over time. Beyond one year, there is no assurance that the UV light emitted from the bulb will provide sufficient disinfection. Remember, UV light cannot be seen. The bulb may still produce light, but not necessarily UV rays. The quartz sleeve does not need replacement unless it gets broken, however, it should be cleaned several times per year (outside only).
Frequently Asked Questions About Ultraviolet (UV) PurificationUltraviolet (UV) light is at the invisible, violet end of the light spectrum. Even though we can't see UV light, we are exposed to UV rays from all light sources, including the sun.
UV-C rays penetrate the cells of harmful bacteria and viruses in our drinking water, destroying their ability to reproduce. Without this ability, these organisms die and no longer pose a health threat. It is a simple but very effective process, with the system destroying 99.99% of harmful microorganisms.
Chlorine changes the taste and odor of water. Chlorinating also produces harmful by-products called Trihalomethanes (THMs) which are linked to incidence of cancer.
No, the UV unit will use about the same amount of energy as a 60 watt light bulb. It is a cost effective, natural way to increase water quality.
UV systems require pre-filtration to maintain effectiveness as sediment and other contaminants in the water can create a "shadow" which prevents the UV rays from reaching and disinfecting the harmful microorganisms.
It is essential that you change your UV lamp annually. The ability of the lamp to emit UV light decreases over one year in operation. Remember - UV light is invisible! Even though the lamp is still glowing after one year, there might not be enough UV light reaching your water to be effective.
The sleeve doesn't need to be replaced unless it is broken, but it will need to be cleaned several times a year in order to keep the bulb effective in delivering high water quality.
A UV water purifier treats micro-biologically unsafe water with germicidal ultraviolet light. The UV wavelength scrambles the DNA of living organisms in the water so that they can no longer reproduce and make you sick. If you drink bacteria-infested water, the organisms can embed in your digestive tract and replicate. Ultraviolet radiation renders bacteria, viruses, parasites, and fungi unable to replicate by damaging the nucleic acids of their DNA.
Ultraviolet Water Treatment Explained
How a UV water purifier works
An ultraviolet (UV) water purifier exposes living organisms, such as bacteria, viruses, or cysts (like Cryptosporidium and Giardia) to a germicidal ultraviolet wavelength. With enough energy, UV radiation at the 254-nm wavelength disrupts the DNA in pathogenic microorganisms so they cannot reproduce. The ultraviolet light prevents bacteria from spreading disease through drinking water.
UV dosage is the measurement of energy (in mJ/cm²) delivered by a UV water purifier. The more dosage provided, the more energy delivered to treat contaminated water. This energy becomes sufficient at a certain threshold to inactivate most of the microorganisms in water.
What does a UV disinfection remove?
UV disinfection deactivates living organisms, such as bacteria, viruses, spores, and cysts, but it does not remove particles from water, add chemicals, or remove bad tastes and odors.
UV disinfection treats water for:
Several years ago, the city of Milwaukee flooded, and cryptosporidium infected the water supply. Cryptosporidium, also known as Crypto, is a parasite that enters the intestinal tract and causes illnesses such as Montezuma's revenge. Crypto is resistant to chlorine used to disinfect city water, and the water in Milwaukee resulted in hundreds of deaths. UV water purification protects you from pathogenic organisms that chlorine cannot kill, like cryptosporidium.
Learn more: How to remove bacteria from your water
What's inside a UV water purifier?
A UV water purifier includes a chamber that encases the quartz sleeve and UV lamp. The glass quartz sleeve holds the UV lamp that emits a germicidal wavelength of radiation (UV-C) to deactivate living organisms. The quartz glass sleeve is transparent to the UV wavelength, which allows UV light to penetrate the glass and disinfect the water. A quartz sleeve protects the UV lamp from the water because water and electricity do not mix well. One or two O-rings seal the whole system together.
UV lamps run on mercury vapor. The mercury vapor is loaded into a UV lamp in the form of little beads. The mercury vapor created from these beads power the lamp. Occasionally, you may see beads rolling around in the lamp.
Are UV water purifiers safe?
UV water treatment is safe. It does not use harmful chemicals or alter the composition of water. A UV sterilizer uses UV-C light to disinfect. UV-C light is harmful to humans just as it is for microscopic living organisms. However, you are not at risk of exposure unless you touch or look at the UV bulb while it is on.
Chlorine treatment is an alternative to UV, but ultraviolet treatment is much safer. Ultraviolet light treats water for protozoa that chlorine disinfection is unable to remove. A UV system is much easier to maintain and safer to use than chemical disinfectants. Treating water with chlorine requires a retention tank and precise injections and solutions. Many wastewater treatment plants now use UV water purification to eliminate harmful chemical by-products in water from chlorine or chloramine treatment.
Are UV water purifiers effective?
UV systems are effective at deactivating 99.99% of living organisms in water. They are designed to run constantly to guarantee the water you use is always safe. Because a UV purifier is not a filter, there is no wastewater or debris left behind to clean out. Every drop of water that enters the UV system is purified.
UV water purifiers vs. water filters
Unlike water filters, a UV water purifier does not remove particles from water. Reverse osmosis systems, ultrafiltration systems, carbon filters, and ceramic filters all separate contaminants from water through tiny pores of a filter or a membrane. UV treatment purifies water by exposing living organisms to ultraviolet light, but it does not filter them out. Water filters do not remove bacteria and viruses with the same effectiveness as UV systems. UV disinfection works alongside water filtration systems to provide clean water.
Learn more about: Reverse osmosis systems | ultrafiltration systems | Activated carbon filters | Ceramic filters
Is UV necessary for a water filter?
UV purification is not necessary for a water filter, but a water filter is necessary prior to a UV system. UV systems are most effective when water is clear, so they must have at least a five-micron pre-filter to prevent living organisms from hiding behind loose particles. You could use a sediment filter to remove dirt and debris from a well water supply or a water softener to reduce iron as prefiltration. A UV purifier is the last thing water passes through on the way to the house.
Test your water quality before you use a UV system to make sure the water does not exceed these levels:
Advantages of a UV water purifier
UV water purifiers provide many benefits over chemical sterilization.
Disadvantages of a UV water purifier
Despite their many advantages, there are a few disadvantages to UV water purifiers compared to other disinfection methods.
When to use a UV purifier
UV purification is the best option any time your water contains bacteria or if you want additional protection in the case of a natural disaster. By the time your city water plant issues a Boil Water Advisory, the water has already been contaminated. Having a UV system keeps your water free of harmful viruses and pathogens when the water supply is compromised.
If you own a private well or your water is stored in a storage tank, you will need a UV water purifier unless you disinfect your water with chemicals. The well owner is responsible for removing bacteria from water, and ultraviolet treatment is the most effective way to do it. A Rusco spin-down filter is an excellent prefilter for well water before UV disinfection.
UV water purifiers for your home
UV systems are POE (point-of-entry), which means you install them before water enters your home to purify the water throughout your house. Most of the time, typical household pressure is enough for a UV system to operate. However, a flow restrictor should be used to ensure water does not flow too quickly through the system. Water must be subjected to UV light for a specified time before it is disinfected. If the flow rate is too high, water flows through the UV system too quickly to be considered safe.
UV water purifiers come in a wide variety. The size UV system you need depends on the flow rate of your water. Sizing according to flow rate allows water to contact the germicidal wavelength long enough to be effective. Like the size, the price of UV systems varies. Typically, a residential UV system costs around $400 or $500.
UV water purifiers for travel
Handheld UV water purifiers are perfect for backpacking, camping, or traveling around the world. The Steripen by Viqua sterilizes water in seconds without exposing you to UV rays. Handheld UV purifiers come as a single system or as a package with a sediment prefilter for water containing a lot of dirt and debris.
How to maintain your UV water treatment system
UV water purifiers last many years, but they require maintenance like any other water treatment system. However, UV systems are easy to maintain and designed to run continually.
Learn more: How to maintain your UV system
If you have any additional questions, please do not hesitate to contact us.