Ozonation is increasingly integrated into wastewater treatment trains to eliminate organic micropollutants, known to induce adverse effects to aquatic organisms. Additionally, ozonation is sometimes applied in water reuse treatment trains for various treatment goals including disinfection and/or micropollutant abatement. While ozonation has been demonstrated to effectively abate micropollutants in wastewater and reduce toxicity for many endpoints, concerns remain regarding the unintended formation of mutagenic (genotoxic) byproducts. Except for some specific known toxic ozonation byproducts, little is known about the formed mutagenic ozonation byproducts. This knowledge is critical to ensure process optimization by meeting treatment goals while minimizing mutagenicity formation.
OzoToxID aimed at developing and implementing a novel bioanalytical strategy, based on effect-directed analysis (EDA) combining toxicological and advanced chemical analysis, to investigate the formation of toxic ozonation byproducts during wastewater treatment.
An integrative approach combining a mutagenicity assay and advanced chemical analysis as well as mechanistic and kinetic assessments were conducted. Additionally, a non-target screening method for carbonyl compounds, a toxicologically relevant chemical class, has been developed.
Overall, the findings from OzoToxID confirmed the systematic formation of mutagenicity during wastewater ozonation. Subsequent sand filtration allowed to either partially or entirely eliminate the mutagenic byproducts. Nitrite concentration, the applied ozone dose, and the Dissolved Organic Matter (DOM) type played a critical role in the formation of mutagenicity during ozonation. The presence of nitrite in wastewater resulted in a higher formation of mutagenic byproducts during ozonation. This was also accompanied by the formation of nitrocompounds from organic precursors, in a pathway which presumably involves nitrogen dioxide (NO2) as nitrating agent. A unique fingerprint was attributed to effluent DOM in the formation of mutagenicity, in contrast to other DOM types (e.g. lake water, gray water), for which only negligible or very low mutagenicity was formed during ozonation. Furthermore, a novel non-target screening method for the analysis of carbonyl compounds has been validated and applied for the assessment of carbonyl compound formation during ozonation of different water matrices.
