High-Resolution Mass Spectrometry Screening of Wastewater Effluent for Micropollutants and Their Transformation Products during Disinfection with Performic Acid

Abstract

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

“…PFA was highly reactive with other organic compounds containing reduced-sulfur or nitrogen moieties (e.g., amoxicillin, ranitidine, and lidocaine). The high consumption of PFA by lidocaine is in accordance with a previous study and can be attributed to the reactivity of the deprotonated tertiary amine group to form lidocaine N-oxide . In contrast, the very low reactivity of tramadol, which also has a tertiary amine group, can be attributed to the absence of its deprotonated form at pH 7.0 (p K a = 9.23) .…”

“…PFA was prepared using a method developed by Kemira (KemConnect DEX) and adapted by Nihemaiti et al, consisting of two steps (31.20 mL of 99% formic acid mixed with 0.15 mL of cold water and 2.65 mL of 98% sulfuric acid and 5.43 mL of this mixture reacted with 6.89 mL of 50% H 2 O 2 for 90 min in an ice bath). The resulting PFA stock solution contained approximately 19.5 ± 1.4 (233.9 ± 16.6 g/L) and 19.2 ± 1.2% (230.4 ± 13.8 mg/L) by weight of H 2 O 2 and PFA, respectively.…”

“…Treated WW effluent was collected from the Seine Amont WWTP located in Valenton, France, as previously described . Samples were collected directly before the discharge channel and were filtered upon arrival in the laboratory through a 0.7 μm glass fiber filter (Whatman).…”

“…The 7 pharmaceutical compounds spiked in WW effluent samples were analyzed by ultrahigh-performance liquid chromatography (UPLC) coupled with tandem mass spectrometry (MS/MS) with triple quadrupole detection (Acquity-TQD, Waters) after extraction using an automated solid-phase extraction (SPE) system (Dionex Autotrace 280, Thermo Scientific) with multilayer SPE cartridges as described previously. , Analytical details (stationary and mobile phases, internal standards, elution gradient, and ionization mode) and the MS/MS acquisition parameters are provided in SI (Text S3, Table S2).…”

“…The analysis was performed in both negative and positive ionization modes, and mass spectra were acquired in HDMS E (data independent analysis) mode to obtain low and high collision energy fragments. All information regarding the instrument parameters and the method was published previously …”