Abstract <p>The overwhelming majority of commercial nonionic surfactants (NIS) represent a mixture of many chemically related compounds, a number of which and some metabolites are resistant to biochemical assimilation and pose a serious threat to living organisms. The degree and efficiency of their removal from water can be increased by combining destructive adsorption methods in water treatment systems, in which the preliminary partial chemical oxidation of resistant compounds leads to the formation of products capable of efficient adsorption and microbial assimilation in an activated carbon (AC) bed at subsequent purification stages. For resistant organic impurities, the degree of their transformation at the previous stage of chemical oxidation is an important technological parameter, which essentially influences the combined water treatment efficiency. Using the “conditional component” method, the effect of the degree of primary NIS (Triton X-100, OP-10) destruction by ozone itself or ozone in combination with UV radiation on the adsorption energy of newly formed mixtures of their decomposition products on activated carbon was studied under isothermal adsorption conditions. The decrease in the equilibrium adsorption values ​​of the reaction mixtures and the change in the molar Gibbs free energy of the adsorption system were estimated with the decomposition of the aromatic ring of NIS in the range of 30–88%. A rational regime without long-term treatment and high specific ozone consumption was proposed for the preliminary oxidation of the studied NIS to increase the bioassimilated organic carbon fraction without absorption system capacity losses.</p>