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

Reactivity of Performic Acid with Organic and Inorganic Compounds: From Oxidation Kinetics to Reaction Pathways

Performic acid (PFA) has gained interest as an alternative chemical disinfectant for wastewater (WW) treatment, but its reactivity with WW constituents remains poorly understood. This study evaluated PFA’s ability to oxidize 45 inorganic and organic compounds commonly found in WW (amino acids, simple organic compounds with specific functional groups, e.g., amines and phenolic compounds, and pharmaceutical micropollutants). PFA does not react with most major ions, except for iodide ions, and reacts with iron­(II) in the absence of phosphate buffer. While many organic molecules do not react with PFA, compounds containing reduced-sulfur moieties (e.g., thioether or thiol) are the most reactive (i.e., ranitidine, benzenethiol, and 3-mercaptophenol), followed by compounds with tertiary amine groups (e.g., lidocaine). The reactions follow second-order kinetics with respect to both organic compounds and PFA concentrations. Similar trends were observed in real WW effluents, although removals of pharmaceuticals were lower than expected due to the probable consumption of PFA by WW constituents (dissolved organic carbon, other micropollutants, or transition metals). The results highlight PFA’s selective reactivity with specific functional groups and a low transformation of compounds mostly through oxygen addition (e.g., S-oxide or sulfonyl compounds formed from thiol and thioether moieties and N-oxides from amine groups) with similar mechanisms to peracetic acid