High-Resolution Mass Spectrometry Screening of Wastewater Effluent for Micropollutants and Their Transformation Products during Disinfection with Performic Acid
Performic acid (PFA) is an emerging disinfectant applied for full-scale disinfection of wastewater effluent. While many studies have focused on assessing the microbial water quality during PFA disinfection, studies on the ability of PFA to oxidize organic micropollutants are still scarce. In this study, nontarget screening of wastewater secondary effluent during PFA treatment was performed using liquid chromatography–high-resolution mass spectrometry. A low dose (2 mg/L) of PFA was able to affect the organic matter composition within a short exposure time (10 min). Multivariate analysis as well as suspect screening indicated that PFA oxidation largely reduced the intensities of micropollutants with a tertiary amine moiety and led to the formation of their mono-oxygenated derivatives, N-oxides, a class of transformation products that are known as biologically stable but whose impact on aquatic organisms still needs to be assessed. Mechanistic studies were conducted on selected micropollutants (i.e., lidocaine, amisulpride, tramadol, and clarithromycin). The minimum apparent second-order rate constant of PFA with lidocaine was determined as 7.54 M–1 s–1 at pH 8.0. Lidocaine was mainly converted (∼95%) into its N-oxide via direct oxygen transfer from PFA. Overall results revealed a strong electrophilic reactivity of PFA toward electron-rich moieties (e.g., amines) of micropollutants.