Into the Light: Europeans have known about the sanitizing power of ultraviolet light for years. Now America is starting to pay attention
Pool & Spa News, May 22, 2006 by Bob Dumas
Page 1 Last summer, one of the nation's largest waterborne parasitic outbreaks in more than 10 years wreaked havoc in upstate New York. More than 3,800 people fell ill between June and August 2005 as a result of cryptosporidium contamination in the holding tanks at Seneca Lake State Park's spraypark near Geneva.
In response, the New York Department of Health created new guidelines and requirements for sprayparks that use recycled water. Part of those mandates is a requirement for ultraviolet light sanitization.
Science has recognized the bactericidal effects of UV for nearly a century. The world's industrial nations have been using it as a drinking water sanitizer for decades, and pool operators in Europe discovered its benefits years ago.
Finally, it would appear that the notoriously skeptical American pool industry may be ready to embrace it as well.
Tom Lachocki, Ph.D., CEO of the National Swimming Pool Foundation in Colorado Springs, Colo., says his organization and the Centers for Disease Control are big advocates of UV sanitization.
"There is a lot of data, precedent and science behind UV," he says. "But the most exciting thing is its ability to inactivate cryptosporidium."
UV can stop crypto almost immediately. If it had been in place at the Seneca Lake facility, chances are the outbreak would have been thwarted. In fact, UV has the same effect on giardia, a protozoan parasite responsible for another notorious recreational water illness called giardiasis.
Service companies are beginning to realize the advantages of working with UV. They say they're getting cleaner, safer pools and happier customers.
"This could change the face of the industry," says John Garvin, president of Tri-City Pool Service in Fort Myers, Fla. "We need to realize its value and begin to promote it more."
So what exactly is ultraviolet sanitization and how does it work? More importantly, what does it mean for you as a service technician? In this article, we'll bring UV sanitization out into the light and attempt to demystify it. It just may prove to be one of the best weapons yet in a service tech's arsenal.
It's scientific
Ultraviolet light is a part of the electromagnetic spectrum that is invisible to the human eye because its wavelengths are too short. Depending upon its specific wavelength measurement, UV light falls into three categories: UV-A, UV-B and UV-C.
UV-A is the type of ultraviolet light that comes from sunlight. As any service tech knows, this kind of light is not good for sanitizer residuals and will increase the rate of chlorine degradation. However, this is not a problem with the light that comes from UV sanitization devices because they use the UV-C wavelength. While this light may create some chlorine loss, it's minimal (2 percent to 5 percent, say experts) compared with natural UV from the sun.
The way UV light goes about its sanitizing business is to break down the DNA of bacteria and the RNA of viruses. Sufficient dosages will prevent the organism from repairing itself, and it cannot replicate. Consequently, adequate exposure of the pool water to UV light is the key to successful sanitization.
It's all about intensity and duration, according to Delta Ultraviolet Corp., a manufacturer of UV pool sanitizers in Gardena, Calif. The water passes through a tube in the device, where it's exposed to the light. The key is how much water is in the chamber and how quickly it passes through
You start with a common intensity, but then you change the diameter and length of the [holding] chamber, which will hold more water for a longer period of time. This has resulted in an array of unit sizes designed to fit various pools with different flow rates.
It's vital that the intensity and exposure be correct because UV light doesn't enter the pool water and stay there. The only opportunity to kill organisms is when they pass by the light.
"UV does not create a residual of light in the water that acts over time," Lachocki says. "Any sanitization or oxidation that occurs happens as it passes [the light]. Once it passes through, that's it."
Thus, it is important to pick a UV sanitizer that fits the pool's circulation system properly--particularly the flow rate and pipe size. Otherwise, the device will not operate efficiently.
The setup
Thanks to most makers of UV-sanitizing units, selecting the right size for a customer's pool is a snap. Most provide a chart or a technical phone support line to assist. All you need to know is the flow rate of the pool's circulation system and its pipe size.
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