Quick Answer: Ozone water purification works by generating ozone (O3) on site from ambient oxygen, dissolving it into water through an injector, and letting it oxidize pathogens and contaminants inside a contact chamber before decomposing back into oxygen. The process runs in five stages: air supply, ozone generation, dissolution, contact time, and off-gas destruction. Ozone destroys bacteria, viruses, and protozoa in under 30 seconds and breaks down chemical contaminants through hydroxyl radical oxidation. Within 1 to 2 hours, residual ozone reverts to oxygen, leaving purified water with zero chemical residues.
Ozone is the strongest commercially available oxidant used in water treatment, but most people do not realize it is manufactured fresh on site, dissolved into water within seconds, and then allowed to revert back to oxygen. Unlike chlorine, it is never stored, shipped, or added as a chemical. The entire process runs on electricity and ambient air inside a closed-loop system. Here is exactly how ozone water purification works, stage by stage, what it destroys, and why industries from water bottling to aquaculture rely on it.
What Is Ozone Water Purification?
Ozone water purification is the process of using ozone gas (O3) dissolved in water to destroy microorganisms, oxidize dissolved metals, and break down organic pollutants. Ozone is a triatomic form of oxygen. A normal oxygen molecule has two atoms, but ozone has three, and that third atom is loosely bonded, making the molecule highly reactive.
When ozone contacts a contaminant, it either transfers an oxygen atom directly (direct oxidation) or decomposes into hydroxyl radicals (OH) that attack contaminants indirectly. Because ozone is highly unstable, it cannot be stored or shipped and must be generated on demand, which is why ozone systems are always paired with an on-site generator. For the full science, see the chemistry of ozone overview.
The 5-Stage Ozone Water Purification Process
Every commercial ozone water purification system runs the same core sequence, from small food-grade installations to large municipal wastewater skids.
Stage 1: Air supply. Ambient air is compressed, filtered, and dried, or pure oxygen is supplied from a cylinder or concentrator. Cleaner, drier oxygen produces higher ozone yields.
Stage 2: Ozone generation. The oxygen passes through a corona discharge cell, where a high-voltage electrical field splits O2 molecules and recombines them into O3.
Stage 3: Injection. The ozone gas is dissolved into the water stream through a venturi injector or fine-bubble diffuser.
Stage 4: Contact tank. Ozonated water sits in a contact chamber where dissolved ozone reacts with pathogens and contaminants, typically for 4 to 10 minutes, depending on the target.
Stage 5: Off-gas destruct. Any undissolved ozone is passed through a catalytic or thermal destruct unit that converts it back to oxygen before venting.
How Does Ozone Destroy Pathogens and Contaminants?
Ozone works through two simultaneous mechanisms. In direct oxidation, the ozone molecule gives up its third oxygen atom to the target, rupturing bacterial cell walls, destroying viral protein coats, and degrading DNA. This is how ozone kills E. coli, Legionella, norovirus, Cryptosporidium, and Giardia in under 30 seconds, compared to the 15 to 30 minutes free chlorine typically requires.
In indirect oxidation, ozone decomposes in water to form hydroxyl radicals (OH), which have an even higher oxidation potential than ozone itself. Hydroxyl radicals break apart dissolved chemical contaminants that chlorine cannot touch, including pharmaceuticals, pesticides, endocrine disruptors, and taste-and-odor compounds like geosmin and MIB. This dual pathway is why ozone is classified as an advanced oxidation process (AOP) and used for both disinfection and chemical contaminant removal in one step, something no other single disinfectant can do.
What Can Ozone Water Purification Remove?
Ozone also destroys bacterial spores and protozoan cysts that survive standard chlorination, and it does so at CT values roughly two orders of magnitude lower than chlorine. In drinking water applications, ozone is often used for primary disinfection and iron or manganese oxidation. In wastewater, it is used for tertiary polishing, micropollutant destruction, color and odor removal, and pathogen inactivation before discharge or reuse.
Is Ozone Water Purification Right for Your Facility?
Ozone water purification makes sense anywhere chemical-free, residue-free treatment is required, or where chlorine-resistant pathogens and dissolved organics are a concern. Typical use cases include water bottling, beverage production, food processing, aquaculture, greenhouse and nursery irrigation, municipal drinking water, industrial wastewater, and car wash water recycling. The upfront equipment cost is higher than a simple chlorine setup, but operating costs are lower because ozone is generated on-site from air and electricity, with no chemical purchasing, storage, or handling.
Purifico ozone systems are built for each of these use cases, with remote monitoring through the ZONE management system for real-time visibility into ozone output and system health. To scope a system for your water volume and contaminants, contact our team for a consultation.
Frequently Asked Questions
How long does ozone stay in water?
Dissolved ozone has a half-life of 20 to 30 minutes at room temperature and neutral pH. Within 1 to 2 hours, it decomposes fully back to oxygen, leaving oxygen-rich water with no residual.
Does ozone water purification require chemicals?
No. Ozone is generated on-site from ambient air or oxygen using only electricity. There are no chemicals to purchase, store, ship, or handle, which also eliminates the regulatory and safety compliance costs associated with chlorine or chlorine dioxide systems.
Is ozone water purification safe?
Yes. Commercial systems include off-gas destruct units that convert any undissolved ozone back to oxygen before venting, keeping ambient air within occupational safety limits. Once in water, ozone decomposes to oxygen, leaving nothing behind.
How big does an ozone water purification system need to be?
System size scales with water flow rate and target contaminants. Purifico offers systems from small SC Series cabinets to HV Series skids producing 32 to 95 pounds of ozone per day for municipal and industrial use, with containerized C Series units available for reservoirs and remote sites.
Does ozone remove chlorine from water?
Yes. Ozone oxidizes free chlorine on contact, which is useful for dechlorinating water before bottling, hydroponic feed, or sensitive industrial processes.
References
- U.S. Environmental Protection Agency, Alternative Disinfectants and Oxidants Guidance Manual
- International Ozone Association, Ozone in Water Treatment
- World Health Organization, Guidelines for Drinking-water Quality
- U.S. Food and Drug Administration, 21 CFR 173.368 Ozone Use in Food