Ozone-based Advanced Oxidation Processes (AOPs) are cutting-edge solutions for treating recalcitrant pollutants—organic compounds resistant to conventional methods, such as pharmaceuticals, pesticides, and industrial solvents. Ozone (O₃), a powerful oxidant, is generated on-site by passing air or oxygen through high-voltage electrodes, then injected into wastewater to initiate radical-driven reactions that break down complex molecules into harmless byproducts like CO₂ and H₂O.
The system typically includes an ozone generator, contactor reactor (e.g., bubble column or packed tower), and residual ozone destructor. In AOPs, ozone may be combined with hydrogen peroxide (O₃/H₂O₂) or UV light (UV/O₃) to produce hydroxyl radicals (•OH), which have a higher oxidation potential (2.8 V) than ozone alone, enabling non-selective degradation of even highly stable contaminants.
Advantages & Applications:
- Rapid Degradation: Ozone reacts instantly with many pollutants, reducing treatment time to minutes compared to hours in biological systems. It is widely used in municipal wastewater reuse plants, semiconductor manufacturing (removing micro-pollutants), and landfill leachate treatment.
- No Secondary Pollution: Ozone decomposes into oxygen, leaving no harmful residues. Unlike chemical coagulants, it does not generate sludge.
- Flexible Integration: AOPs can be applied as a standalone process or combined with biological/physical treatments for multi-stage purification.
Challenges:
- High Energy and Cost: Ozone generation requires significant electricity (0.6-1.2 kWh/kg O₃), and the system demands corrosion-resistant materials (stainless steel, titanium) due to ozone’s reactivity.
- pH and Temperature Dependence: Optimal performance occurs at pH 7-9, and efficiency decreases in cold water (below 10°C).
- Safety Considerations: Ozone is toxic at high concentrations, necessitating strict safety protocols for storage and handling.
