title: Determination of oxidant exposure during ozonation of secondary effluent to predict contaminant removal.
abstract: The use of kinetic models to predict oxidation performance in wastewater is limited due to fast ozone depletion during the first milliseconds of the reaction. This paper introduces the Quench Flow Module (QFM), a bench-scale experimental technique developed to measure the first 5-500 milliseconds of ozone depletion for accurate determination of ozone exposure in wastewater-ozonation processes. Calculated ozone exposure in QFM experiments was up to 24% lower than in standard batch experiments, strongly depending on the initial sampling point for measurement in batch experiments. However, oxidation rates of slowly- and moderately-reacting trace organic compounds (TrOCs) were accurately predicted from batch experiments based on integration of ozone depletion and removal of an ozone-resistant probe compound to calculate oxidant exposures. An alternative concept, where ozone and hydroxyl radical exposures are back-calculated from the removal of two probe compounds, was tested as well. Although the QFM was suggested to be an efficient mixing reactor, ozone exposure ranged over three orders of magnitude when different probe compounds reacting moderately with ozone were used for the calculation. These effects were beyond uncertainty ranges for apparent second order rate constants and consistently observed with different ozone-injection techniques, i.e. QFM, batch experiments, bubble columns and venturi injection. This indicates that previously suggested mixing effects are not responsible for the difference and other still unknown factors might be relevant. Results furthermore suggest that ozone exposure calculations from the relative residual concentration of a probe compound are not a promising option for evaluation of ozonation of secondary effluents.
authors.affiliation: School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel; The Hydro-Chemistry Laboratory, Geography and the Environment, Tel Aviv University, Tel Aviv 69978, Israel; The Water Research Center at Tel-Aviv University, Israel. Electronic address: ineschay@post.tau.ac.il.
authors.forename: Ines
authors.initials: I
authors.lastname: Zucker
authors.affiliation: The Hydro-Chemistry Laboratory, Geography and the Environment, Tel Aviv University, Tel Aviv 69978, Israel; The Water Research Center at Tel-Aviv University, Israel.
authors.forename: Dror
authors.initials: D
authors.lastname: Avisar
authors.affiliation: School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel; The Water Research Center at Tel-Aviv University, Israel.
authors.forename: Hadas
authors.initials: H
authors.lastname: Mamane
authors.affiliation: Technical University of Berlin, Department of Water Quality Control, Str. des 17 Juni 135, 10623, Berlin Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Jekel
authors.affiliation: Technical University of Berlin, Department of Water Quality Control, Str. des 17 Juni 135, 10623, Berlin Germany; Technical University of Munich, Chair of Urban Water Systems Engineering, Am Coulombwall 3, 85748, Garching Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Hübner
mesh_terms: D009930:Organic Chemicals; D016877:Oxidants; D010084:Oxidation-Reduction; D010126:Ozone; D014865:Waste Disposal, Fluid; D062065:Wastewater; D014874:Water Pollutants, Chemical
chemical_list: D009930:Organic Chemicals; D016877:Oxidants; D010126:Ozone; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Depletion; Oxidant exposure; Probe compound; Quench flow; Trace organic compound