Ozone and chlorine reactions with dissolved organic matter - Assessment of oxidant-reactive moieties by optical measurements and the electron donating capacities

WATER RESEARCH

卷:144

Article

Onnby, Linda¹  Salhi, Elisabeth¹  Mckay, Garrett²  Rosario-Ortiz, Fernando L.²  von Gunten, Urs^1,3,4 

[1] Eawag, Swiss Fed Inst Aquat Sci & Technol, CH-8600 Dubendorf, Switzerland

[2] Univ Colorado, Dept Civil Environm & Architectural Engn, Environm Engn Program, Boulder, CO 80309 USA

[3] Swiss Fed Inst Technol, Inst Biogeochem & Pollutant Dynam, CH-8092 Zurich, Switzerland

[4] Ecole Polytech Fed Lausanne, Sch Architecture Civil & Environm Engn ENAC, CH-1015 Lausanne, Switzerland

关键词: Dissolved organic matter;    Electron donating capacity;    Oxidant reactivity;    Ozone;    Chlorine;    Disinfection by-products;    Fluorescence;   

DOI  :  10.1016/j.watres.2018.06.059

来源: Elsevier

【 摘 要 】

Oxidation processes are impacted by the type, concentration and reactivity of the dissolved organic matter (DOM). In this study, the reactions between various types of DOM (Suwannee River fulvic acid (SRFA), Nordic Reservoir NOM (NNOM) and Pony Lake fulvic acid (PLFA)) and two oxidants (ozone and chlorine) were studied in the pH range 2-9 by using a combination of optical measurements and electron donating capacities. The relationships between residual electron donating capacity (EDC) and residual absorbance showed a strong pH dependence for the ozone-DOM reactions with phenolic functional groups being the main reacting moieties. Relative EDC and absorbance abatements (UV254 or UV280) were similar at pH 2. At pH 7 or 9, the relative abatement of EDC was more pronounced than for absorbance, which could be explained by the formation of UV-absorbing products such as benzoquinone from the transformation of phenolic moieties. An increase in fluorescence abatement with increasing pH was also observed during ozonation. The increase in fluorescence quantum yields could not be attributed to formation of benzoquinone, but related to a faster abatement of phenolic moieties relative to fluorophores with low ozone reactivity. The overall (OH)-O-center dot yields as a result of DOM-induced ozone consumption increased significantly with increasing pH, which could be related to the higher reactivity of phenolic moieties at higher pH. The (OH)-O-center dot yields for SRFA and PLFA were proportional to the phenolic contents, whereas for NNOM, the (OH)-O-center dot yield was about 30% higher. During chlorination of DOM at pH 7 an efficient relative EDC abatement was observed whereas the relative absorbance abatement was much less pronounced. This is due to the formation of chlorophenolic moieties, which exert a significant absorbance, and partly lose their electron donating capacity. Pre-ozonation of SRFA leads to a decrease of chloroform and haloacetic acid formation, however, only after a threshold of > similar to 50% abatement of the EDC and under conditions which are not precursor limited. The decrease in chloroform and haloacetic acid formation after the threshold EDC abatement was proportional to the relative residual EDC. (C) 2018 Elsevier Ltd. All rights reserved.

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