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Ultraviolet Water Treatment – The Case for Using UV

Ultraviolet (UV) water treatment is both an exciting and somewhat mysterious way to sanitize water. In recent years, it’s become widely used in managing swimming pool water because it’s been proven an effective way to control pathogens without adding any chemicals to the water whatsoever.

It also offers other benefits such as destroying chloramines and controlling ozone off gassing by turning it into hydroxyl radicals through the even more mysterious set of chemical reactions collectively known as “advanced oxidation process.” (We’ll talk about AOP in a future blog.)

For those reasons, UV has become a key component in our company’s approach to ensuring superior water quality for our clients. Like all the treatment methods we use, UV doesn’t offer all the answers, but it does play a role in meticulous water treatment.

I first learned about UV back in 2002 when my son and I visited the Mystic Sea Aquarium in Mystic, Connecticut. I’ve always loved aquariums and have long been interested in how they keep the waters clear while harboring all those fish and other sea creatures. (Talk about “bather load”—aquariums maintain clear water while serving as full-time homes for scores if not hundreds of animals. That’s impressive to say the least.)

UV and Ponds and Aquariums

At one of the tanks while my son was marveling at the fish, I noticed columns of bubbles that I immediately gathered were part of the treatment scheme, not unlike the way home aquariums are oxygenated with bubblers. But off to the side I noticed a box with all these tubes feeding into it. I didn’t know what it was, but I immediately recognized the company name emblazoned on the side, Pentair. Given that’s a brand I associate with swimming pool equipment, I couldn’t help but wonder what kind of Pentair product was being used on a large-scale aquarium.

Turns out, it was a UV system. That spurred my interest, and I soon delved into what UV was all about. There’s quite a lot to understanding UV but long story short, back in those days it was a treatment method largely associated with treating water in ponds as well as aquariums.

That all made sense because in those “naturalistic” systems, the idea is to treat water without using halogens, such as chlorine, because it will kill fish and plants. As it happened, back then UV was starting to also be used on swimming pools because of its effective way of stunting the growth of pathogens, which proponents of the technology point out is a great way to reduce chlorine consumption in pools.

And although UV does not provide any kind of sanitizing residual or oxidize anything, for many professionals, its work on harmful microorganisms justifies the expense of installing it on pools and even some spas.

I began experimenting with the technology and quickly recognized how when combined with other treatment methods, it could dramatically improve water quality. I understood from the start, however, that it is not a stand-alone treatment method.

A Natural Companion

It can be tricky to explain how UV works. I’ve seen many descriptions, and this one from explains it as well as any I’ve found:

Ultraviolet (UV) light is energy within the electromagnetic spectrum that has shorter wavelengths than that which are visible to the human eye. UV light is a range of electromagnetic waves from 100 to 400 nanometers (between x-ray and visible light). The division of UV light is classified as Vacuum UV (100-200 nm), UV-C (200-280 nm), UV-B (280-315 nm) and UV-A (315-400 nm). The energy waves provided in the UV-C spectrum demonstrate the germicidal efficiencies that provide highly effective disinfection.

To be perfectly honest, all these years later I’m still working to fully understand the nuances of UV treatment, but through extensive practical evaluation and lots of trial and error, we have learned to apply UV to our treatment systems in a way that serves as a perfect complement to our ozone and chlorine treatment systems.

I do know that UV kills pathogens not by lysing them the way chlorine or other oxidizers do, but instead by scrambling their DNA so they can’t reproduce. UV has long been proven effective in reducing pathogen numbers to harmless levels when used properly.

In another blog, I discussed why I am so devoted to using ozone as part of a treatment system. In the SRK HydroZone 3® system, we create a bypass loop that uses an ozone generator and a contact tank to treat 25 percent of the circulation. For that 25 percent, ozone does an amazing job of oxidizing organic compounds and killing microorganisms. The remaining 75 percent is sanitized using UV, which is installed downstream of the ozone bypass.

In our systems, ozone handles the lion’s share of oxidation, while UV handles the sanitizing.

UV also has the added benefit of destroying excess ozone before it re-enters the pool, which has major implications for indoor pools, especially where ozone off gassing can be dangerous and is prohibited.

In other words, the two technologies complement each other. Neither would be nearly as effective without the other. UV is a perfect role player—and that’s why SRK Pool Services uses UV!



A blog about all things water, written by SRK's founder Steve Kenny.