The synthesis of new compounds used in various fields of human activity requires completely new purification technologies. The paper presents new technologies of detoxification and disinfection of pollutants under the influence of UV irradiation developed by us and tested in industrial and natural objects. The efficiency of purification was controlled by biotesting methods that allow quantifying the total toxic effect of the initial DCS and products of their transformation. It was shown that the effect of UV light with λ = 254 nm or in the near UV region (λ> 340 nm) on benz (a) pyrene (BP) in the sorbed state leads to its direct photolysis. Under the influence of visible light (λ> 430 nm), BP is effectively oxidized only in the presence of a sensitizer. The results of the study indicate that the toxic effect of PAHs may be associated with their participation in the initiation of OH radicals directly in the nonpolar phase of biological macromolecules. In the absence of sensitizers, the source of singlet oxygen can be hydrogen peroxide, for example, during its catalase intracellular decomposition. A method of combined purification of mixed municipal and industrial wastewater with UV treatment and subsequent biological purification in an aerotank has been developed. Production tests of this method were carried out at the wastewater treatment plant of Belgorod. The result is an improvement in the functional state of activated sludge microorganisms, an increase in the throughput of aerotanks by 30-50% while improving the cleaning parameters according to generally accepted indicators. Conclusion: before supplying wastewater to the aeration tanks of treatment plants, it is necessary to treat them with hydrogen peroxide in combination with UV radiation (λ≥220 nm) with intensive aeration. The technology of disinfection of natural drinking waters from surface water sources with the use of UV radiation from low-pressure mercury lamps – instead of primary chlorination has been developed. The technology has passed successful production tests at the Pervomaisk drinking water treatment plant in Nizhny Novgorod. The figure shows: a cassette of UV-radiation lamps in a quartz casing and a drinking water flow at the Pervomaiskaya treatment plant in Nizhny Novgorod, passing through a system of cassettes. This technology is also applicable for disinfection of wastewater after its biological treatment using the original design of water-submersible UV installations of tray-type. Under the influence of UV radiation, nitrate and nitrite ions serve as initiators of free radical processes in the aquatic environment. A method for the denitrification of wastewater containing nitrate and nitrite ions, simultaneously with destructive purification and detoxification of multicomponent effluents due to the photoinitiation of OH-radicals, leading to a symbatic decrease in the concentration of the toxicant, toxicity and denitrification has been developed. Photoozoning technology in combination with subsequent microbiological treatment with immobilized adapted bacterial strains for destructive purification and detoxification of wastewater containing difficult-to-decompose surfactants has been developed. With microbiological degradation of photoozonation products, the toxicity of anionic surfactant solutions decreases by 2-3 times, and in the case of nonionic surfactants – until complete detoxification.