title: Production of photo-oxidants by dissolved organic matter during UV water treatment.
abstract: Dissolved organic matter (DOM) irradiated by sunlight generates photo-oxidants that can accelerate organic contaminant degradation in surface waters. However, the significance of this process to contaminant removal during engineered UV water treatment has not been demonstrated, partly due to a lack of suitable methods in the deep UV range. This work expands methods previously established to detect (1)O2, HO•, H2O2, and DOM triplet states ((3)DOM*) at solar wavelengths to irradiation at 254 nm, typical of UV water treatment. For transient intermediates, the methods include a photostable probe combined with selective scavengers. Quantum yields for (1)O2, (3)DOM* and H2O2 were in the same range as for solar-driven reactions but were an order of magnitude higher for HO•, which other experiments indicate is due to H2O2 reduction. With the quantum yields, the degradation of metoxuron was successfully predicted in a DOM solution irradiated at 254 nm. Further modeling showed that the contribution of DOM sensitization to organic contaminant removal during UV treatment should be significant only at high UV fluence, characteristic of advanced oxidation processes. Of the reactive species studied, (3)DOM* is predicted to have the greatest general influence on UV degradation of contaminants.
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado , UCB 428, Boulder, Colorado 80309, United States.
authors.forename: Yaal
authors.initials: Y
authors.lastname: Lester
authors.forename: Charles M
authors.initials: CM
authors.lastname: Sharpless
authors.forename: Hadas
authors.initials: H
authors.lastname: Mamane
authors.forename: Karl G
authors.initials: KG
authors.lastname: Linden
mesh_terms: D000042:Absorption; D006812:Humic Substances / Q000032:analysis; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D009930:Organic Chemicals / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry*; D010782:Photolysis / Q000528:radiation effects; D011789:Quantum Theory; D026082:Singlet Oxygen / Q000737:chemistry; D012995:Solubility; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D018508:Water Purification
chemical_list: D006812:Humic Substances; D009930:Organic Chemicals; D016877:Oxidants; D014874:Water Pollutants, Chemical; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide