Ozonation is a chemical water treatment technique based on the infusion of ozone into water. Ozone is a gas composed of three oxygen atoms (O3), which is one of the most powerful oxidants. Ozonation is a type of advanced oxidation process, involving the production of very reactive oxygen species able to attack a wide range of organic compounds and all microorganisms. The treatment of water with ozone has a wide range of applications, as it is efficient for disinfection as well as for the degradation of organic and inorganic pollutants. Ozone is produced with the use of energy by subjecting oxygen (O2) to high electric voltage or to UV radiation.
The formation of oxygen into ozone occurs with the usage of energy. By an electric discharge field as in the CD-type ozone generators, this process is carried out, or by ultraviolet radiation as in UV-type ozone generators. Adding to these commercial methods, ozone may also be made through chemical reactions and electrolytic. Typically an ozonation system includes passing dry, clean air through a high voltage electric discharge, i.e., corona discharge, that creates and ozone concentration of approximately 1% or 10,000 mg/L. UV ozonation is the most common in treating small quantities while large-scale systems use either corona discharge or other bulk ozone-producing methods. The raw water is then passed through a venturi throat that creates a vacuum and pulls the ozone gas into the water or the air is then bubbled up through the water being treated.
Because of its excellent disinfection and oxidation qualities, ozone is widely used for drinking water treatment. Ozone can be added at several points throughout the treatment system, such as during pre-oxidation, intermediate oxidation, or final disinfection. Usually, it is recommended to use ozone for pre-oxidation, before a sand filter or an active carbon filter (GAC). After ozonation, these filters can remove the remaining organic matter (important for final disinfection).
This combination has several benefits:
- Removal of organic and inorganic matter
- Removal of micro-pollutants, such as pesticides
- Enhancement of the flocculation/coagulation-decantation process
- Enhanced disinfection and reduction of disinfection by-products
- Odor and taste elimination