A comprehensive analysis of storage impact on toxicity assessment of ozonated effluents

Neglecting the time intervals between sampling and biological testing can lead to misinterpretation of the hazards associated with advanced oxidation processes when assessed through bioassays. This study investigates changes in the non-specific toxicity of ozonated aromatic compounds and analyzes the factors such as temperature and light exposure influencing these changes during sample storage. The findings reveal a significant decrease in biotoxicity of ozonated effluents, ranging from 41 % to 83 %, within the first four days of storage at 22 °C under natural light exposure. A lumped acute toxicity attenuation model was developed to describe the reduction process, showing that temperature markedly affects both the attenuation rate constant and amplitude, while natural light exposure does not. Using fluorescence spectroscopy and mass spectrometry, primary toxic byproducts, particularly p-benzoquinones, were identified and found to be substantially eliminated during storage, accompanied by a notable linear increase in fluorescence intensity. The transformation of p-benzoquinones occurred via hydroxylation and reduction reactions, with theoretical calculations demonstrating a decrease in the toxicity of the resultant products. Overall, these insights highlight the importance of standardized sample storage in accurately assessing the biotoxicity of effluents from advanced oxidation treatments, providing critical guidance for bioassay evaluations.