In the title process, com. CaO2 (purity 75%) was used as a source of H2O2 for removal of org. impurities (COD) from wastewater. The COD in the wastewater under optimum conditions of the UV/H2O2 process (CaO2 addn. 2.0 g/L, pH 1.5, reaction time 60 min) and of the Fenton process (CaO2 addn. 4.0 g/L Fe2+/CaO2 ratio 0.2, pH 2.5, reaction time 75 min) was reduced by 71.4% and 92.4% resp. In both cases, the BOD5/COD ratio increased from 0.015 to 0.11 and 0.37 resp., and wastewater became more susceptible for biodegrdn.