title: Impact of hydrodynamics on pollutant degradation and energy efficiency of VUV/UV and H2O2/UV oxidation processes.
abstract: The Vacuum-UV/UV process, an incipient catalyst/chemical-free advanced oxidation process (AOP), is potentially a cost-effective solution for the removal of harmful micropollutants from water. Utilizing a novel mechanistic numerical model, this work aimed to establish a thorough understanding of the degradation mechanisms in the VUV/UV process operating under continuous flow conditions, when compared with the widely applied H2O2/UV AOP. Of particular interest was the examination of the impact of flow characteristics (hydrodynamics) on the degradation efficacy of a target micropollutant during the VUV/UV and H2O2/UV AOPs. While hydroxyl radical (OH) oxidation was the dominant degradation pathway in both processes, the degradation efficacy of the VUV/UV process showed much stronger correlation with the extent of mixing in the photoreactor. Under a uniform flow regime, the degradation efficiency of the target pollutant achieved by the H2O2/UV process with 2- and 5 ppm H2O2 was greater than that provided by the VUV/UV process. Nonetheless, introduction of mixing and circulation zones to the VUV/UV reactor resulted in superior performance compared with the H2O2/UV AOP. Based on the electrical energy-per-order (EEO) analysis, incorporation of circulation zones resulted in a reduction of up to 50% in the overall energy cost of the VUV/UV AOP, while the corresponding reduction for the 5-ppm H2O2/UV system was less than 5%. Furthermore, the extent of OH scavenging of natural organic matter (NOM) on energy efficiency of the VUV/UV and H2O2/UV AOPs under continuous flow conditions was assessed using the EEO analysis.
authors.affiliation: Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Bagheri
authors.affiliation: Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada. Electronic address: madjid.mohseni@ubc.ca.
authors.forename: Madjid
authors.initials: M
authors.lastname: Mohseni
mesh_terms: D002723:Chlorobenzoates / Q000737:chemistry; D057446:Hydrodynamics; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D012996:Solutions; D014466:Ultraviolet Rays; D014618:Vacuum; D014865:Waste Disposal, Fluid / Q000191:economics / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002723:Chlorobenzoates; D012996:Solutions; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; C040768:4-chlorobenzoic acid
keywords: Advanced oxidation; Flow characteristics; H(2)O(2)/UV; Micropollutants; Numerical modeling; Vacuum-UV/UV