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Studies show that one in four wells in the U.S. will test positive for coliform bacteria. This alarming statistic underscores the importance of proper disinfection and accurate, periodic water testing. Ultraviolet (UV) light has been used since the early 20th century to disinfect water, but increased consumer awareness about waterborne pathogens — such as E. coli and Cryptosporidium — has led to a rising demand for UV systems in private homes.
Unlike other disinfection methods, such as chlorination, UV does not require the use of potentially harmful chemicals. So while chemical disinfection opens consumers up to possible adverse effects from overtreatment, the potential for overtreatment with UV is virtually nonexistent.
“The nice thing about UV is that you’re not adding anything to the water, so you can’t really over-treat with ultraviolet,” says Bruce Eccleston, president of UV Superstore. “If you’re pumping a certain amount of chemical based upon a 100 gpm flow rate and you’re actually having 5 gpm going through there, that water [is] going to have an excessive amount of chemicals in there for what it needs.”
While UV is much more effective at reducing coliform bacteria and cysts, it is not the right treatment for every application. For example, UV light is not as effective on water that has high levels of tannins, such as that found in Florida.
Furthermore, explains Eccleston, areas with extremely hard water are not ideal for UV systems. A UV lamp is enclosed in a protective quartz sleeve, but if scale builds up on the sleeve it can have a negative effect on the lamp’s ability to disinfect. “If your quartz sleeve gets any buildup or biofouling on there — maybe you have really hard water and you get a scale that starts building up on the quartz sleeve — the UV light can’t penetrate through it to disinfect the water properly,” he says. However, he adds, scaling can be minimized if the proper pretreatment is employed.
While ultraviolet (UV) disinfection systems are quite common in Canada, well owners in the U.S. need to be better educated on the necessity for disinfection.
“In Canada, when they drill a well, it’s almost always a given that the consumer understands that they’re going to need some form of protection on their well. And, typically, that protection is UV,” explains Steve Stone, North American sales manager for VIQUA. “In the U.S., the consumer is not educated to the point to where they understand the need for disinfection.”
Stone emphasizes that water treatment dealers, plumbers and drillers need to help customers understand the importance of well testing and make them aware that quick fix, “band-aid” solutions are not in their best interest.
Nick Phillips is a previous editor of Water Technology.