Decomposition of micropollutants and changes in the toxicity of water matrices subjected to various oxidation processes

The generation of toxic by-products is an adverse effect that accompanies the processes of chemical oxidation, which is increasingly being used to eliminate organic micropollutants from wastewater. This paper concentrates on assessing the elimination of selected organic micropollutants (bisphenol A, 17α-ethinylestradiol and 17β-estradiol) and evaluating the changes in the toxicity of wastewater after various oxidation processes (UV, UV/O₃, UV/TiO₂) that were conducted for 30 min for comparative purposes. The toxicity of wastewater was assessed with the help of selected indicator organisms (bacteria, crustacea, a water plant) from different taxonomic groups. Regardless of the type of researched oxidation process, the effectiveness of micropollutant elimination increased with time, and oestrogens (17α-ethinylestradiol, 17β-estradiol) were more susceptible to degradation than bisphenol A. Nevertheless, after every oxidation process, the wastewater was toxic to one or more groups of indicator organisms. Among the researched oxidation processes, the most efficient process for degrading micropollutants was the UV/O₃ process. The wastewater treated by this process was toxic only to bacteria, which was the most sensitive group among the indicator organisms. This paper also presents an interesting phenomenon regarding the influence of an environmental matrix on observed toxicity.