Ozone systems for beginners

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Courtesy of Zentox Corporation

This paper is intended for people who know a cooling tower when they see one but have little or no knowledge of their care or what part ozone plays. I have tried to make this as simple as possible and there is even a block diagram on the last page to help you out. Ready? Okay, here is what you need to know first: The sole function of ozone use in evaporative cooling towers is to disinfect water. That’s all. Period. There are many strange ideas about ozone. It is not magic. It will not destroy the ozone layer. It does not prevent corrosion or scale, not directly, anyway. Ozone just disinfects water and makes it clean. Very clean. The magic is in what you can do with very clean water.

Ozone is a unique chemical in that it is made from the oxygen in the air, and turns back into oxygen after about twenty minutes in the average cooling tower. So ozone can’t be stored; it must be generated on-site. Ozone is an oxidizing biocide, which means it kills all microbes, such as bacteria, viruses, spores and algae. An important difference between ozone and traditional chemicals is that ozone kills by oxidation (burning) rather than poisoning, which is how chemicals work, so no organism can become immune to ozone, as often happens with conventional chemicals. Incidentally, pound for pound, ozone is about 5 times more effective than chlorine.

An ozone treatment system is composed of components to compress room air, dry it, concentrate it to 90-95% oxygen, and from that oxygen generate ozone and mix it with the water in the cooling tower. A side stream is established between the cooling tower sump and the ozone system with PVC pipe. (please refer to the block diagram) A circulating pump in the ozone system runs continuously to circulate water through the side stream. The pump moves water from the tower sump to the ozone system, past a conductivity probe and an ORP probe, through the ozone injector, then back to the tower basin. There are two controllers: a conductivity controller and an ORP controller, and a probe is connected to each.

Okay so far? Then let’s see what all these components do and how they work together. The ORP probe measures the amount of ozone in the water and reports it to the ORP controller, which is a small, cube-shaped, industrial computer. ORP means Oxygen Reduction Potential. It is basically a measure of the ability of ozonated water to oxidize organic matter, and serves as a reliable indicator of how much ozone is in the water at any given instant. When the ORP reaches “setpoint,” (the low or high preset limit) the controller responds by adjusting the output of the ozone generator to bring the ORP back within limits. This throttling of the ozone generator occurs constantly to insure that exactly the right amount of ozone is always present in the water. (cruise control for your cooling tower!)

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