Abstract <p>The development of new light sources (excimer, xenon, etc.) has enabled the use of vacuum radiation for the disinfection of natural and waste household and industrial water. Many papers are devoted to the modeling of photocatalytic oxidation systems, but they insufficiently highlight the effect of ultraviolet radiation on the processes occurring in the reactor when water structures in the surface water microlayer are activated. For this reason, the development of a model of calculating the effective radiation and energy effect parameters as a function from the absorbance of a treated liquid and the size of a reflector for surface irradiating water treatment systems is relevant. Just the vacuum ultraviolet quantity is a crucial factor in the synthesis of hydroxyl and peroxyl radicals immediately in water. In this paper, theoretical models and algorithms are proposed for the calculation of photocatalytic water treatment reactors with non-immersed radiation sources in the optimal UV radiation utilization regime. The applied oxidizers are known reagents, such as hydrogen peroxide, ozone, etc. Among all the reagents, ozone has the highest oxidation potential in water treatment. The possibilities of water treatment under the cumulative effect of photocatalytic ozone and UV radiation with the use of corresponding excimer lamps have been determined. For the system of irradiation with non-immersed light sources, it seems most promising to use photocatalytic ozone formed from oxygen under the influence of UV light radiation with wavelengths of 100–200 nm.</p>