Swimming Pool and Spa Equipment – Ozone Generators

If you have been doing some research on Ozone, you have no doubt already read many articles describing its properties. Very simply, it is 3 oxygen atoms that were combined through one of several processes. It becomes a very unstable molecule in this state, and is just waiting for a chance to stabilize again by oxidizing something, almost anything actually.

What we want to do with the Ozone we produce will play a big part in which process we use to make it. Here, we are concerned with water, but Ozone also has many other uses. How we make the Ozone will determine how powerful it is. Then the biggest issue is how we will apply it. You can take the finest Ozone producing equipment available, and render it next to useless if it is not applied properly. A few issues to be concerned with are concentration, solubility and contact time. There are the UV style Ozone generators (the bulb/lamp style), which do not use air preparation systems, and Corona Discharge (so called lighting storm style) ones that do. Although sometimes used without air prep. Systems, CD style generators should always use prepared air or oxygen to produce ozone. Humidity in the air will cause the process to create nitric acid which will destroy the generator in a short time. Humid air also produces very little ozone.

Solubility is important, because if we can’t dissolve the Ozone in the water, it won’t work. Just bubbling some ozone into the water may dissolve some ozone, but much will be wasted and just off gas to atmosphere. Without a long explanation, this is where venturi injectors are so effective. They literally squeeze the Ozone into the water. We also want the bubbles to be as small as possible because there is more surface area in many small bubbles then in large. Again, the venturi injectors are very good at this. In dealing with concentration, what we want to accomplish is getting those bubbles to contain the most ozone they can. The more Ozone a bubble contains the more oxidizing power it has. Oxygen of course, has more oxygen in it to produce ozone than air, and no humidity, so we get a much higher concentration. Dried air has less humidity than room air, so we again get higher concentrations. Taking a Corona Discharge generator and using oxygen as a feed gas, we will get by far the highest concentration.

If we took 1 gram of ozone and put it in 1 big bubble, there would be a lot of ozone in the bubbles interior not able to contact anything. If we took that same gram and put it into 1000 tiny bubbles, the increased surface area allows more ozone molecules to react with something, and so very little ozone would be wasted as off gas.

As with chlorine, bromine or any other sanitizer or oxidant, Ozone has a time that it takes to kill or oxidize a given thing. This is known as contact time. The molecule will come in contact with something, and after a certain period, that something is eliminated. The most powerful, commonly used product used we are familiar with is chlorine. Ozone has 100 times the oxidizing power of chlorine. It also kills bacteria and cysts etc. up to 3,000 times faster. Residuals and kill rates are calculated at CT Values, which is the Concentration multiplied by the exposure time. If we look at the Giardia Cyst in water at 68o F with a pH or 7.5, we will find that free chlorine has a CT value of 83 to obtain a given inactivation of the cyst. Ozone has a CT value of .72. This means that a 1ppm, free chlorine will take 83 minutes to perform this feat, whereas 1ppm Ozone will take only about 40 seconds.

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