Here’s another inquiry from a Subscriber: “I have a hot tub. The hot tub has an “ozone generator” which creates a steady stream of small bubbles through the pool. The recommended treatment system is bromine, which I am maintaining according to instructions — and they say that the ozone will make it possible to use fewer chemicals. How is ozone as a water treatment method, how is it generated, what are the risks, if any, and can it be used in drinking water systems?”
Well, starting with the last question, ozone is used a lot in drinking water systems. In fact, it is one of only four chemicals (with chlorine, chloramines, and chlorine dioxide) that is explicitly approved as a drinking water disinfectant.
The bromine that you are using is another effective disinfectant, but it is not approved for drinking water. It has a significant advantage of its disinfectant “cousin,” chlorine, in that it is odorless. In fact, it is used for disinfection at Universal Studios in some of their water attractions — like Jurassic Park — because they didn’t want the obvious smell that chlorine disinfection would produce. And that makes sense for a hot tub too.
All chemical disinfectants are “oxidants,” and will engage in similar chemical reactions in the water. So adding ozone will reduce the need for bromine. In theory, you could use either by itself. But ozone provides a couple of noteworthy advantages, especially for a hot tub: it is the most effective chemical of the four approved disinfectants; it is also the fastest-acting. In a small system like a hot tub, fast action is very helpful. What bromine might disinfect adequately in 20 – 30 minutes, ozone could handle in about 20 – 30 seconds. So I would say ozone is great for an operating hot tub with people in it.
For small systems like this, ozone is usually made by irradiating compressed air with ultraviolet light. The bubbles that you note are from the compressed air. About one-half of one percent of that air is ozone. Prolonged exposure to gaseous ozone can cause headaches and irritation of the mucous membranes. I would not expect this to be much of a risk in a hot tub setting for two reasons: first, “prolonged” exposure is more than a few hours — longer than most folks will stay in or around the tub; and second, the amount of ozone that actually makes it into the air above your hot tub should be pretty low. In fact, it may be less than in the Los Angeles smog you breath in on a regular basis!
Enjoy your ozone/bromine hot tub. Sounds like you have an excellent disinfection system in place. Now all you need is some free time and a cold one!