In general, oxidation is a chemical reaction in which the oxidized element or compound gives off electrons and passes into a higher valence stage. Oxidizing agents are thus substances that absorb electrons and are themselves reduced in the process.
Frequently used oxidizing agents in practice are chlorine (Cl2), ozone (O3), chlorine dioxide (ClO2), potassium permanganate (KMnO4) and hydrogen peroxide (H2O2). The oxidizing agents are added to the water, for example by means of metering pumps, and mixed in. After an oxidation, water constituents are generally easier to separate off, followed by a corresponding further processing stage for separating off the substances. Depending on the nature of the water, it should be noted that undesirable by-products can also form during the oxidation processes.
Oxidation by UV light can also be used for disinfection purposes. The UV radiation causes a photochemical reaction in the DNA (deoxyribonucleic acid) of microorganisms within seconds. As a result, the microorganisms are either killed immediately (direct cell death) or lose their ability to multiply (indirect cell death). In the UV systems, no chemicals are added to the water, so that no unwanted by-products can arise.