Ozone vs UV
The two key technologies that form the mainstay of the discussion around secondary disinfection are UV and ozone. While UV has been relatively well understood by aquatics designers and operators, ozone, a rapidly-advancing technology, has been given less attention despite the many compelling reasons to choose ozone over UV.
What is Ozone?
Ozone is a gas that is dissolved in water to kill microorganisms, destroy organics, and break down chloramines by oxidation. This occurs immediately at the ozone gas injection point, and continues as the side-stream remixes with the main return. A small residual (~0.1 PPM) of dissolved ozone will enter the pool, providing further oxidation of contaminants.
What is UV?
UV light inactivates microorganisms and breaks down chloramines with light energy. This happens while the water is in the UV chamber only, and as long as the water has no turbidity. No further primary sanitation process occurs once the flow leaves the chamber. UV provides no oxidation except as trace amounts as a result of the formation of a limited number of hydroxyl free radicals in or near the UV chamber.
Comparing Ozone and UV:
There is sometimes confusion as to the difference between ozone and UV systems. Actually, they are completely different technologies, however the confusion may stem from UV-generated ozone that was popular in residential pools and spas until the late 1990s when breakthrough compact CD ozone generators took over that market. UV generated ozone is never used on a public pool because the systems cannot make enough ozone to benefit the pool water. CD generated ozone, on the other hand, is extremely safe and effective for pool water sanitation.
Ozone is a gas that is dissolved in water to kill microorganisms, destroy organics, and break down chloramines by oxidation. In comparison, UV light inactivates microorganisms and breaks down chloramines with light energy. With UV, this chloramine breakdown only happens while the water is in the UV chamber, and as long as the water has no turbidity. With Ozone, oxidation occurs immediately at the ozone gas injection point and continues as the side-stream remixes with the main return.
While both Ozone and UV provide very effective Crypto reduction as documented by third-party testing and validation, there are distinct differences between the two technologies when it comes to other areas of concern for commercial aquatics designers and operators, with clear advantages to Ozone over UV.
Ozone is a powerful oxidizer.
Ozone gas dissolves in water to kill microorganisms, destroy organics that create chloramines, and breaks down existing chloramines by oxidation. This oxidation happens immediately at the ozone gas injection point and continues as the side-stream remixes with the main return. A small residual (~0.1 PPM) of dissolved ozone then enters the pool, providing further oxidation of contaminants. There are no consumables in an ozone system.
Meanwhile, UV light inactivates microorganisms and breaks down chloramines with light energy. This happens only while the water is in the UV chamber, and as long as the water has no turbidity. Once the flow leaves the chamber no further process occurs. UV provides no oxidation except as trace amounts as a result of the formation of a limited number of hydroxyl free radicals.
Ozone and UV are comparable in cost.
Ozone and UV technologies are comparably priced. Operational costs of each system vary with the local price of electricity. However, the minimal maintenance and reduced chemical requirements of an ozone system create significant benefits. Meanwhile, UV lamps must be replaced every 3 to 12 months and must be figured into the maintenance costs for these systems.
| Ozone | UV |
|---|---|
 Ozone kills cryptosporidium parvum |
 UV inactivates cryptosporidium parvum |
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Ozone kills microorganisms |
UV inactivates microorganisms |
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Ozone is a powerful oxidizer |
UV is not an oxidizer |
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Ozone passes into the pool at low levels to provide additional oxidation |
UV affects the water only as it passes through the UV chamber |
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Ozone functions well in cloudy water and is a micro-flocculent, which aids water clarity |
Only clear water can be effectively dosed with UV; cloudiness in the water can absorb the UV light |
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Ozone oxidizes the organics and inorganics that create chloramines, eliminating their production |
UV breaks down chloramines that have been previously created |
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Ozone utilizes ORP (REDOX) to measure the cleanliness of the water |
UV systems utilize a UV intensity meter which measures the UV dose regardless of water quality |
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Ozone’s reaction with free available chlorine (FAC) is very slow and in a pool will not affect the FAC levels; only chloramine destruction |
UV can break down free available chlorine in the water while it breaks down chloramines |
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Ozone cells require no replacement; require annual periodic cleaning; no hazardous components |
Mercury vapor lamps are replaced @ 3-12 mos.; disposal procedures must be considered as lamp gases are considered hazardous waste |
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Ozone destroys biofilm |
UV does not affect biofilm |
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Ozone destroys Humic and Fulvic Acid |
UV does not affect Humic and Fulvic Acid |
Learn More About Ozone:
The DEL Ozone Aquatics Program is Easy as 1-2-3:
1. Request a quote. We’ll size your system according to MAHC guidelines and send a quote right away.
2. We’ll deliver and commission your pre-installed system within one to two months.
3. Begin to enjoy the improvements to your water quality and your facility right away.
