Ozone is an unstable gas produced as a result of the dissociation of trivalent oxygen molecules in the atomic oxygen and is characterized by a strong oxidizing power. It is mainly used in the disinfection, controlling agents which give to water flavor, odor and color, or for the advanced removal of organic refractory soluble compounds.
In the textile industry it is mainly used as decoloring agent and as an agent for reducing foam. In the foremost case, the ozone acts on the chromophoric group of the dye molecule, breaking the chemical double link and, thus, disabling the refraction of light that generates the perception of color. As result, you obtain a not colored water, although the dye molecule remains dissolved and present in the water.
The reduction on the COD, with the dosages normally used for decoloration, is about 10-15%. The foams are broken down almost totally.
This process generates a discharge free from color, from foams and with a concentration of COD partially reduced.
Ozonation systems generally consist of the following units:
- Energy generator, for converting oxygen into ozone O3;
- System for the air treatment, to dehumidify and to filter the air inlet (not necessary when you use pure oxygen;
- Area for ozone generation. Since ozone is a very unstable compound from the chemical point of view, it must be produced on site by high voltage electrical discharges and dosed in the liquid to be treated through micro bubbles diffusers, to increase as much as possible the surface of contact;
- Equipment for putting the ozone in contact with the liquid to be treated, thereby maximizing the transfer efficiency of the gas in the liquid;
- A system for the distruction of residual ozone, to avoid the emission into the atmosphere, since it is a toxic and highly irritating gas.
However this solution has a very effective bactericidal and virucidal power, higher than the system with chlorine dosing. It has the advantage of not producing waste sludge and is not influenced neither by the pH, nor by the concentration of ammonium ions.