Comparative non-target screening of advanced oxidation process (AOP)-integrated industrial wastewater treatment using RP and mixed-mode chromatography.

Advanced oxidation is increasingly integrated into industrial wastewater treatment to address complex, variable contaminant loads. Here, LC-HRMS non-target screening (NTS) was used to characterize an industrial WWTP incorporating a one-stage advanced oxidation process (AOP) and to compare reversed-phase (RP) and mixed-mode (MM) chromatography for expanding the accessible polarity window. Both methods delivered consistently high data quality, enabling robust feature-level comparisons. Cliff's δ and polarity descriptors indicated differences in feature distributions, while tentative matching to the NORMAN Substance Database suggested substantial overlap between RP and MM and pointed to potential database bias toward less polar compounds. Multivariate analyses captured treatment-driven chemical patterns: PCA separated AOP-treated samples most clearly with MM, consistent with enhanced sensitivity to polar transformation products, whereas RP more strongly differentiated influent from effluent, reflecting predominantly hydrophobic signals. PLS-DA confirmed these trends and enabled robust classification of sample types. Volcano analyses highlighted statistically significant increases, decreases, and persistent signals, showing that while biological treatment removed most components, a subset of AOP-derived features persisted into the final effluent. Overall, broadening the chromatographic window improves NTS-based process assessment and supports targeted optimization of treatment steps for problematic compounds.