This monograph is focused on the study of the possible utilization of the biological degradation of wastes from the machining industry with the prior application of selected advanced oxidation processes. In the theoretical part it brings an overview to the state of the art of the current biodegradability tests available for the testing of poorly soluble or adsorbing substances such as metalworking fluids are. In experimental part a preliminary study of the ozone application sole or in the combination with ultraviolent irradiation or Fenton like processes are conducted to investigate how these can affected the level of the biological degradation. For the measurement of the biodegradability, carbon dioxide produced by the microbial consortium in a closed apparatus was choosing as the main parameter. For this purpose a special closed apparatus was build up and its suitability was evaluate. In the case of sole ozone application unfortunately in 8 of 11 tested samples were observed reversed trend, the degradability after ozone application decreased. In the case of combined application of ozone and UV irradiation only in one sample of total 6 was the biodegradability increased. Finally combined application of ozone and Fenton’s like processes was the biodegradability level increased by 23 % in compare to non-treated sample.