Pool Sanitizers: Ozone vs UV vs AOP vs Ionizers
Pool Sanitizers: Ozone vs UV vs AOP vs Ionizers

Cleaning your swimming pool is as important as keeping your house in order. Sanitizing your pool water regularly is essential not just for your health but also to ensure your comfort, to protect your equipment, and to save you money by avoiding pool repairs.

Chlorine is the most common chemical used to disinfect swimming pools. Chlorine chemistry keeps the pool water free from bacteria that can be hazardous to you and your family. However, chlorine and its byproducts can cause many harmful effects not only to the body but also to the health of the people who swim in pool water with such chemicals. Because of this, there has been awareness in the past few years about their usage.

Apparently, you can have sanitized pool water without using the typical chlorine sanitizing treatments. There are many pool sanitizers that can be used instead of chlorine but Ozone, UV, AOP and Ionizers stand out as the most effective and practical.


Chemicals in water

When a disinfectant combines with organic material or other chemicals present in pool water, it causes the formation of unwanted chemicals called Disinfection by-products (DBPs). Exposure to DBPs may cause risk to humans but it’s inevitable due to continuous disinfection of swimming pool water and constant organic loading from those who swim in the pool.

These DBPs exist as three different forms of chloramines – monochloramine (NH2Cl), dichloramine (NHCl2) and trichloramine (NCl3).

DBPs are also referred to as trihalomethanes (THMs). It is when an organic matter in the water combines with chlorine. Chlorine was widely used as a disinfectant but it causes foul odors, skin, eye and ear irritation, swimmers asthma, and can even damage indoor air-handling systems (HVAC). For this reason, we search for alternatives to chemicals and their resulting by-product in order to have pool water that is safe to swim in. 



Ozone (O3) is a powerful oxidizer that sanitizes and disinfects the water quickly and effectively to kill dangerous pathogens and microorganisms, destroy organics and inorganics and break down chloramine levels in the water to 0.2 ppm or less through oxidation which happens when an ozone molecule collides with an oxidizable substance, such as bacteria, mold, algae, urine, sweat, spores, and protozoa.

Ozone is an unstable molecule that has three oxygen atoms wherein the third atom is connected only to the other two atoms by a weak bond. The third atom combines with organic and inorganic molecules to break and destroy them in pool and spa water. This process reduces the consumption of chlorine by 50-75 percent.

Ozone is 200 times stronger than chlorine. It kills waterborne pathogens that chlorine can’t effectively eliminate like cryptosporidium parvum. It can also destroy human fluids, cosmetics and organics of all kinds. Ozone systems are simple, compact and energy efficient. It is a viable water quality solution that polishes water for a crystal clear pool water at an affordable cost.



Ultraviolet is one of the best technologies for pool water disinfection. It disinfects the water using 200 - 400 nanometers UV-C, which is also referred to as germicidal UV, to ruin 99.9% DNA or RNA of bacteria, viruses, algae, mold spores, protozoa, chloramines and other living microorganisms in the water. The UV rays kill or inactivate their ability to survive and reproduce, keeping the pool water clearer without adding additional chemicals, gases or oxidants to the water.

UV systems are also considered a great introduction to advanced sanitizer systems. The ultraviolet sanitizer unit is installed inline and operates with the filter pump cycle. The UV light sanitizes the pool water by penetrating the cells of the microorganisms as they pass through the UV chamber.

UV-C alone cannot disinfect a swimming pool entirely without the use of chlorine but it lowers chlorine usage by 25-50 percent. Although UV-C does not produce ozone and does not oxidize, it also has an ability to inactivate stubborn diseases like Cryptosporidium and Giardia.



Are you torn between Ozone and UV? Why not choose AOP? Advanced Oxidation Process or AOP is treating the water using the combination of the ozone and UV technology to maximize disinfection, water clarity, and chloramine removal. In an AOP system, the ozone gas is dissolved in the water and then the ozonated water goes through UV-C treatment. The combination of the two water treatments can create a chemical reaction resulting in hydroxyl radicals. The more ozone molecules in the system, the more it’ll form hydroxyl radicals.

Hydroxyl radicals are very powerful oxidants that can effectively kill many harmful pollutants including some pathogens that traditional chlorine treatments cannot remove. Hydroxyl-based AOP system is a safe water treatment because it works fast and has gone fast since it has a short lifespan. It quickly converts back into oxygen after they oxidize pollutants in the water. AOP also has the lowest chlorine requirement but it provides three times the oxidation potential as chlorine which makes the water not only looking clear but also feeling fresh and smelling clean.

AOP treatment can be a bit confusing due to the fact that there are two different systems involved but its methods utilize a unique, clear comfort patented process instead of treating the water directly with ozone and UV. It allows pool and spa owners and operators to enjoy a clear and soft pool water with lesser hassle since the system can be easily mounted outside of the pool or spa plumbing configuration.



If you’re looking for a pool sanitizer that will allow you to sanitize your swimming pool with less harsh chemicals, pool ionizer is what you need. It is a device that uses electricity to produce mineral ions—specifically, copper and silver which are effective in eliminating bacteria and preventing algae in the water. This pool mineral sanitizer is more effective at keeping pools sanitized than higher levels of chlorine alone.

Compared to chlorine, ionizers make the water softer and gentler on skin, hair, and eyes. However, pool ionizer cannot fully sanitize a pool on its own. You must supplement with another sanitizer such as chlorine or bromine to break down organics from bathers and the environment. Without a supplemental sanitizer, ionizers work very slowly so the larger the pool, the longer it takes. Ionizers also cannot oxidize contaminants as they are not powerful enough to kill a wide spectrum of microbial organisms.

According to NSF, EPA and other governing bodies, using an ionizer also allows you to reduce your chlorine usage down to 0.5ppm.


The Differences

The main difference between the four water sanitizers is their way of killing microorganisms. UV uses light energy to do so while Ozone kills them by oxidation. AOP is the combination of the two systems. Meanwhile, Ionizers use mineral ions.

In terms of maintaining these sanitizers, the UV system is easy to install and very easy to maintain. Its quartz tube just needs to be cleaned annually and the UV lamps should be replaced once their effectiveness has diminished. The Ozone system allows less spending on chemical treatment and ozone cells typically are replaced 10 years or more. Pool Ionizer cells need to be replaced every few months to every few years. Its expenses are often lower than UV systems and ozone generators. Meanwhile, the aluminum cartridge of AOP only requires one yearly replacement.


When it comes to history, Ozone is the one that has been around the longest. For the past 100 years, it has been used to sanitize municipal water which is used in commercial aquariums and zoos. Ozone is also the primary supplemental sanitation technology for the hot-tub industry. However, ozone has less acceptance in the commercial pool world compared to UV due to the misconceptions about what ozone is, how it works, and how it compares to UV. On the other hand, AOP has been used for more than 30 years in wastewater but has only recently become an affordable option for residential pools. It is kind of similar to the copper and silver water sanitization which was first discovered during the time of ancient Greeks and Egyptians. Then, it was developed by NASA during the 1960s for water treatment on space missions. Since the 1970s, Metal Ionization technology has been used for pool water treatment.



Ozone, UV, AOP and Ionizer sanitizer technologies improve and enhance pool water through different ways but all these ways are better than a residual sanitizer alone. In order to keep your pool safe for swimming, you have to use at least one of these pool sanitizers. They are safe, effective and reliable methods of water sanitation so no matter which treatment system you choose for your pool water, all of them can surely eliminate chlorine byproducts and help make pools healthier and easier to manage. However, it’s essential to understand the difference between these sanitizers for you to choose which sanitation method is best for your own pool. Keep in mind that each method has its pros and cons. You have to be mindful about how these methods work to achieve your goal of making the water safer for swimming.