Dissolved Organic Matter-Mediated Photosensitized Activation of Monochloramine for Micropollutant Abatement in Wastewater Effluent.

Utilizing solar light and water matrix components in situ to reduce the chemical and energy demands would make treatment technologies more sustainable for micropollutant abatement in wastewater effluents. We herein propose a new strategy for micropollutant abatement through dissolved organic matter (DOM)-mediated photosensitized activation of monochloramine (NHCl). Exposing the chlorinated wastewater effluent with residual NHCl to solar irradiation (solar/DOM/NHCl process) degrades six structurally diverse micropollutants at rate constants 1.26-34.2 times of those by the solar photolysis of the dechlorinated effluent (solar/DOM process). Notably, among the six micropollutants, the degradation rate constants of estradiol, acetaminophen, bisphenol A, and atenolol by the solar/DOM/NHCl process are 1.13-4.32 times the summation of those by the solar/DOM and solar/NHCl processes. The synergism in micropollutant degradation is attributed to the generation of reactive nitrogen species (RNS) and hydroxyl radicals (HO) from the photosensitized activation of NHCl. Triplet state-excited DOM (DOM*) dominates the activation of NHCl, leading to the generation of RNS, while HO is produced from the interactions between RNS and other photochemically produced reactive intermediates (e.g., O and DOM). The findings advance the knowledge of DOM-mediated photosensitization and offer a sustainable method for micropollutant abatement in wastewater effluents containing residual NHCl.