During an oxidation treatment, depending of the degradation pathway of the organic compound in study, more toxic compounds can be formed. To assess the effluent risk to environment, biodegradability and toxicity of samples were monitored along the experimental time. Biodegradability and toxicity tests were performed for slag/H2O2/UV and slag/H2O2. To better analyze the influence of both methods on the biodegradability of the samples, results are expressed as BOD5/TOC. Toxicity results are also expressed as 1/EC50 in order to make the values directly proportional to toxicity. Fig. 6 shows the biodegradability and toxicity of the samples along the reaction time for the slag/H2O2/UV.