Abatement of micropollutants and formation of transformation products in municipal wastewater effluent during ozonation: Complementarity of targeted and non-targeted analyses

A comprehensive approach combining target analysis, non-target screening, and suspect screening was employed to assess the effectiveness of ozonation in removing micropollutants at their native concentrations from wastewater effluent, using HPLC-HRMS. Eight pharmaceutical micropollutants were monitored during the wastewater ozonation to evaluate their removal efficiency at different ozone doses. A specific transferred ozone dose of 1.10 g_O3.g_C^-1 was sufficient to eliminate over 90 % of seven of the compounds. Non-target screening revealed that the greatest number of ozonation transformation products formed at a low ozone dose of approximately 0.52 g_O3.g_C^-1. Increasing the ozone dose led to further degradation of these transformation products. Suspect screening identified 15 OTPs with confidence levels of 3 or higher. The formation kinetics of these compounds were assessed based on their chromatographic peak areas. Primary transformation products from highly ozone-reactive compounds were most abundant at lower ozone doses, whereas those derived from less reactive compounds formed at higher ozone doses. The integration of multiple analytical approaches highlighted both the effectiveness of ozonation for micropollutant removal at economically sustainable doses and the importance of better understanding and monitoring ozonation transformation products during ozonation and in subsequent treatment processes.