Though it’s been used for decades, ozone is gaining traction as a solution in pool sanitation, offering an effective and eco-friendly addition to traditional chlorine-based methods. As more pool professionals and homeowners seek sustainable and efficient ways to maintain pristine water quality, understanding the basics of ozone production, its advantages and the challenges it presents is crucial.
What is ozone?
Ozone (O3) is a powerful oxidizing agent formed when oxygen (O2) molecules are split by high-energy electrical discharges, such as lightning strikes, resulting in individual oxygen atoms. These atoms combine with O2 in weak bonds to form O3, or ozone.
“It is very chemically unstable,” says Steve Barnes, director of science and compliance at AquaStar Pool Products in Ventura, California. “It’s not a happy relationship. So that single oxygen molecule is looking to find something more appealing, and it will attack anything and everything, which makes ozone an extremely powerful oxidizer.”
“Anything and everything” includes bacteria, viruses, fungi and algae, making ozone’s oxidizing properties useful for pool sanitation. Its utility is not confined to pools but also extends to industries like wastewater treatment or food processing and bottling as recognized and approved by organizations including the Environmental Protection Agency, Centers for Disease Control and Prevention and the Food and Drug Administration.
What is Ozone? Ozone is formed when oxygen (O2) molecules are split by high-energy electrical discharges resulting in individual oxygen atoms. These atoms combine with O2 in weak bonds to form O3, or ozone.
How is ozone produced?
Ozone is generated using two primary methods: ultraviolet light and corona discharge.
The ultraviolet method involves a UV bulb that splits oxygen molecules when they pass through its light, initiating ozone production. One drawback is the difficulty in determining the bulb’s effectiveness because it continues to emit light even when not producing ozone, as UV bulbs degrade over time. Pros and homeowners should follow the manufacturers’ guidelines for replacing the bulbs and not simply rely on whether the bulb is still burning.
Corona discharge compactly mimics lightning, splitting oxygen molecules and using a venturi injector — a device that mixes liquids or gasses into a stream of water using differential pressure — to introduce ozone into the pool water. While UV ozone generators are generally less expensive and easier to maintain, corona discharge generators can produce a higher concentration and quality of ozone.
Advantages of ozone
Ozone offers several advantages over traditional chlorine sanitization. First, it is 60-120 times faster in killing bacteria, significantly reducing chlorine demand.
“It does the job faster — it neutralizes the variety of things in the water, from nitrates to germs and [microorganisms], bacteria and algae — therefore, there is less work for the chlorine to do,” Barnes says.
However, chlorine remains necessary as the primary sanitizer, since ozone performs most of its work in the pipes.
“Ozone will never replace the primary sanitizer because it’s not going to be out in the pool,” Barnes says.
Anthony Levacque, an engineer at Fluidra, also emphasizes ozone as a secondary sanitization option.
“Ozone effectively destroys 99.9% of harmful contaminants as the water passes through the filtration system and before it enters the pool — allowing there to be more free chlorine in the pool,” he says.
Ozone’s breakdown into oxygen and CO2 means there are no harmful byproducts, and it does not raise total dissolved solids levels. It also effectively addresses both organic and inorganic compounds.
By reducing chlorine demand and avoiding byproducts, ozone proves superior to simple UV sanitization. Barnes explains this with an illustration envisioning bacteria as a grape.
“Basically, ozone comes in and it smashes the grape,” he says. “It destroys the outer shell and then kills it, whereas UV sanitization sterilizes the cell, so it can’t reproduce, but it doesn’t kill it. It’s still in the water.”
As a microflocculant, ozone also enhances water clarity and reduces odors.
“Once that grape has been popped, the mass that’s left starts to collect together and gets caught in the filter,” Barnes says.
This process creates a better swimming experience.
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When pool water is treated with ozone, the look, the feel and the quality of the water are spectacular.”
Beth Hamil, Beth Hamil o3 Consulting
“When pool water is treated with ozone, the look, the feel and the quality of the water are spectacular — people notice,” says Beth Hamil, a veteran of DEL Industries and current owner of Beth Hamil O3 Consulting.
Challenges of using ozone
Despite its benefits, ozone systems present challenges, notably their high upfront costs. Since ozone decomposes quickly, it must be generated on-site with sophisticated equipment. Regular maintenance is essential, particularly cleaning the venturi injector, which can become clogged with oxidized minerals and calcium.
“The problem is, when the venturi injector is plugged up, it no longer draws ozone through the corona discharge or the UV bulb, so the system quits making and injecting ozone through no fault of ozone and no fault of the original equipment,” Barnes says.
To keep an ozone generator running smoothly, the venturi injector should be cleaned quarterly, and for ozone to be effective, the pool’s pump must run consistently.
“The key to success with ozone is to run your pump very slow most of the day and bump it a couple of times a day,” Barnes says.
Innovations in ozone systems
While there are many ozone systems on the market, AquaStar’s PureStar ozone system was built to address these challenges. It is a corona discharge system with a self-cleaning venturi injector, simplifying maintenance and ensuring efficiency. It’s designed to be a plug-and-play system compatible with variable-speed pumps and retails for between $1,000-$1,200.
Fluidra offers two ozone-related product families — DEL ozonators and advanced oxidation process systems, which combine ozone and UV to produce hydroxyl radicals, the most potent oxidation agents available.
Levacque says these devices use corona discharge technology to produce significantly more ozone than other UV methods. “It’s a big plus for the pool owner to use this technology,” he says. “It’ll help them save money on chlorine and the chemicals they use.”
With unstable chlorine prices, ozone systems are becoming more attractive for their cost-efficiency and improved water quality. The systems are also appealing to those interested in sustainable options.
“Ozone is safe, sustainable, organic and the most environmentally friendly antimicrobial oxidizer available,” Hamil says.
