Ozonation in water treatment: ozone production, fundamental properties, and practical applications
Introduction
Ensuring access to safe and high-quality water is a major public health and environmental challenge worldwide. Among the various water treatment technologies, ozonation has proven to be particularly effective due to the strong oxidizing properties of ozone. Ozone (O₃) has been used for decades in drinking water and wastewater treatment because of its ability to disinfect water and remove a wide range of chemical and biological contaminants. This article presents the main methods of ozone production, its fundamental properties, and its practical applications in water treatment.
1. Ozone production
1.1. General principles
Ozone is a highly reactive and unstable molecule composed of three oxygen atoms. Because it rapidly decomposes back into oxygen, ozone cannot be stored and must be produced directly at the site of use. Its formation is based on the dissociation of oxygen molecules (O₂) followed by the recombination of atomic oxygen with molecular oxygen to form ozone.
1.2. Ozone generation methods
The most widely used method for ozone generation in water treatment is corona discharge. This process involves passing a high-voltage electrical current through dry air or pure oxygen. The electrical energy breaks oxygen molecules into individual atoms, which then react to form ozone.
The simplified reactions are as follows:
- O₂ → 2 O•
- O• + O₂ → O₃
Other methods, such as ultraviolet radiation or electrochemical generation, are also known. However, they are generally limited to small-scale applications due to lower efficiency and higher operational costs.
2. Fundamental properties of ozone
2.1. Physical and chemical characteristics
Ozone is a pale blue gas with a sharp, characteristic odor. It is highly unstable and decomposes rapidly in water, especially at higher temperatures and alkaline pH values. Although its solubility in water is limited, it is sufficient to ensure an effective reaction with contaminants during treatment.
2.2. Oxidizing power
Ozone is one of the strongest oxidizing agents used in water treatment, with an oxidation potential significantly higher than that of chlorine. This high reactivity allows ozone to oxidize a wide range of substances, including:
- pathogenic microorganisms,
- organic compounds responsible for color, taste, and odor,
- various chemical pollutants such as pesticides, pharmaceuticals, and other micropollutants.
2.3. Disinfection efficiency
Ozone acts rapidly on microorganisms by damaging cell membranes and disrupting vital enzymatic processes. It is particularly effective against chlorine-resistant pathogens such as Giardia and Cryptosporidium. As a result, ozonation provides a high level of microbial safety in water treatment systems.
3. Practical applications of ozonation in water treatment
3.1. Drinking water treatment
In drinking water treatment plants, ozone is commonly used for:
- primary disinfection,
- removal of unpleasant tastes, odors, and color,
- oxidation of iron, manganese, and certain organic compounds.
Ozonation is often combined with other treatment steps such as coagulation, filtration, and final disinfection (e.g., chlorination) to ensure both immediate and long-term protection of the water distribution network.
3.2. Wastewater treatment
Ozone is also applied in advanced wastewater treatment, particularly as a tertiary treatment process. It helps reduce pathogenic microorganisms and degrade persistent organic contaminants. This application is especially relevant for water reuse in agriculture and industry.
3.3. Advantages of O3
Advantages:
- high disinfection efficiency,
- effective removal of taste- and odor-causing compounds,
- no long-lasting chemical residues in treated water.
Conclusion
Ozonation is a highly effective and well-established technology in water treatment. Thanks to its strong oxidizing and disinfecting properties, ozone significantly improves both the sanitary and aesthetic quality of water. However, its application requires careful technical control and proper integration into treatment systems. In the future, ozonation is expected to play an increasingly important role, particularly in addressing emerging contaminants and supporting sustainable water reuse strategies.