Suspect screening of micropollutants and their transformation products in advanced wastewater treatment.

Transformation products (TPs) of organic micropollutants are still rarely considered in monitoring of wastewater and aquatic environments. For example, occurrence data of ozonated TPs in full-scale wastewater systems is largely lacking. In this study, the efficiency of a suspect screening strategy including 245 previously reported compounds and their TPs was evaluated for assessing the occurrence of different compound classes and their ozonated TPs in wastewater samples collected at different steps of an advanced treatment process including ozonation. After applying blank subtraction and filtering by mass accuracy (5ppm tolerance), peak height (minimum 1000 counts) and isotopic pattern score (≥80%) 189 of the 245 compounds were detected. A decrease in relative concentration levels was observed for parent compounds in wastewater after ozonation and after a subsequent biological treatment process, while formation of tentative TPs after ozonation accompanied by subsequent degradation in a following biological treatment step was found. Plausibility of structural assignments for tentatively identified TPs could be successfully tested by using relative retention time information as comparison criteria. Overall, the screening approach was fast and successful and can be expanded to other compound classes and TPs where reference standards are not readily available.