Taking the UV Plunge
This year, my family took the plunge and became proud owners of a new swimming pool. Because I am in the ultraviolet (UV) water disinfection business as well as the owner of a spa tub, I thought that maintenance would be a no-brainer. I told my wife not to worry about a thing because I thought I had everything under control. Well, let’s just say that it was a painful and expensive learning experience.
Anyone who has had a pool knows that maintenance is both extremely important and time-consuming. Weekend swimmers take a lot for granted—whether we are going to the public swimming pool or over to a friend’s house, we assume that the water is safe.
In order to get a better handle on what I needed to know about pool maintenance, I contacted Jim Tanner, one of the UV experts in Siemens’ leisure aquatics business, for an education in Pool UV 101. The information he provided helped me get my home situation under control and better understand how larger pools handle these same, and even more complex, issues.
From what I have learned, there are two major areas where UV can be effectively used in a pool environment. One is for disinfection and the other is for the destruction of chloramines (smells and chemical odors).
The use of UV to treat swimming pool water is similar to using UV light to disinfect drinking water. The UV lamps used for germicidal disinfection produce a portion of light in the 254-nm wavelength and can be either low- or medium-pressure lamp technology.
The 254-nm wavelength is in the UVC range of light. At this wavelength, UV light destroys bacteria, protozoa, viruses, molds, algae and other microbes. This includes fecal coliform and waterborne diseases such as E. coli, hepatitis, cholera, dysentery, typhoid fever and many others.
Using UV for the swimming pool does not necessarily mean the complete elimination of chlorine. A residual is still required, but using UV for disinfection will lower chemical cost and usage, provide instantaneous disinfection (chemicals require a residence time), lower disinfection byproducts (that occur when chemicals interact with organics and have been associated with cancer) and provide for less intensive maintenance.
Once installed, UV will be effective at destroying waterborne disease-causing microorganisms. UV systems are sized with the idea that the water will be turned over at least four times a day. Depending on the pool, chlorine can be reduced by 50%. This treatment is effective for home pools, municipal pools and indoor aquatic centers.
Chloramines are a significant problem for indoor aquatic centers. Their formation is responsible for the chemical smells that we associate with indoor swimming pools. My assumption had always been: If it smells like chemicals, then the water has to be clean; however, it turns out that what we think is a chlorine smell is actually chloramines.
The formation of chloramines occurs when there is not enough free chlorine in the pool. Free chlorine will oxidize organics such as sweat, body oils, fecal contaminants and ammonia/nitrogen compounds. Without enough free chlorine, you cannot oxidize these compounds. What happens is that the chlorine actually bonds with these organic materials and forms the chloramines. This is why you get odor, which also cause eye, skin and respiratory irritation.
UV light has the ability to destroy chloramines in the same basic way that it does microorganisms. The main difference is that destruction of chloramines requires a different type of lamp. While 254 nm is the effective wavelength for germicidal disinfection, chloramines destruction requires 250 to 385 nm. These particular wavelengths come from medium-pressure lamp technology.
Medium-pressure systems can provide both germicidal as well as chloramines reduction in the same system, which makes them attractive for all swimming pools. When correctly applied, chloramines can be reduced by 75%.
When treating home pools, you can work with your water technology professional to design and install a system without too many issues. When dealing with public pools, you need to look at NSF standards.
NSF, the health and safety testing organization, has established a protocol for validating UV systems for swimming pool use. NSF/ANSI Standard 50—Circulation System Components and Related Materials for Swimming Pools, Spas/Hot Tubs—is the validating standard for UV usage for public pools.
With more than half of the states requiring NSF Standard 50 for public pools, it is critical for the public to look for the NSF Standard 50 mark on UV systems. The validation protocol tests for construction, efficacy (biological testing) and operational issues and will ensure swimming centers get an appropriately designed system.
After numerous trips to the pool store, lots of chemical concoctions, test kits and strips and a nicely tinted green pool, we took Tanner’s advice and installed a UV system. I took a 50-gpm commercial unit out of stock and plumbed it inline after my filtration unit. I piped it using 2-in. PVC piping and plugged it in.
The first test: a birthday pool party for my six-year-old son and 20 of his closest friends. The result: a great day for the kids, fewer chemicals and no more green water.