**Abstract**

Considering the nature of organic contaminants in water, methods of their oxidative decomposition seem to be most appropriate for their removal from contaminated water. There are a lot of methods of chemical oxidation, however, Advanced Oxidation Processes (AOPs) seem to be the most suitable technologies for organic contaminants removal. AOPs belong to a group of processes that efficiently oxidize organic compounds towards harmless inorganic products such as water or carbon dioxide. The processes have shown great potential in treatment of pollutants of low or high concentrations and have found applications for various types of contamination. The hydroxyl radical (•OH) is oxidizing agent used at AOPs to drive contaminant decomposition. It is a powerful, non-selective chemical oxidant, which reacts very rapidly with most organic compounds. Another strong oxidizing agent, singlet oxygen, can be generated by photosensitization of phthalocyanines. Phthalocyanines are molecules based on pyrrol structures connected mainly with methionine groups (–CH=) having a metallic central atom. Illumination upon specific wavelengths initiates formation of singlet oxygen that attack organic contaminants.

**Keywords:** hydroxyl radicals, singlet oxygen, advanced oxidation processes, photosensitization, oxidation
