Dissolved organic matter (DOM)-mediated photosensitized activation of peracetic acid (PAA) for micropollutant abatement in wastewater effluent

Photochemically produced reactive intermediates (PPRIs, e.g., triplet state dissolved organic matter (3DOM*)) from sunlight excitation of DOM are known to activate oxidants (e.g., peroxymonosulfate and hydrogen peroxide) for micropollutant degradation. This study explored the degradation of naproxen, a model micropollutant, by the DOM-mediated photosensitized activation of peracetic acid (PAA) using a real wastewater effluent and a reference DOM isolate (SRNOM). Although DOM is known to reduce oxidant photolysis and scavenge reactive species, this study found that it enhanced the degradation of naproxen in sunlit PAA solutions by 7–13% (Figure 1(a)). In the sunlit solution containing SRNOM and PAA (solar/SRNOM/PAA solution process), direct photolysis, PPRIs, hydroxyl radicals, and organic reactive species (ORS) contributed 27.3%, 2.9%, 19.1%, and 50.8% to naproxen degradation, respectively (Figure 1(b)). Notably, the degradation rate constant attributed to ORS was 50% higher in the solar/SRNOM/PAA solution process (0.15 h–1) compared to the scenario without DOM (0.10 h–1, the solar/PAA solution process). This indicates that the presence of DOM enhances the generation and concentration of ORS in sunlit PAA solutions, which could be attributed to the activation of PAA by PPRIs. Using duroquinone as a model photosensitizer, we verified that 3DOM* contributes to the PAA activation. Overall, this study provided a green method for micropollutant abatement in wastewater by making use of sustainable sunlight and residual PAA in PAA-disinfected wastewater.