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Medium pressure UV combined with chlorine advanced oxidation for trichloroethylene destruction in a model water.

Department of Civil Engineering, University of Toronto, 35 St. George St., Toronto, Ontario M5S 1A4, Canada.
Water Research (Impact Factor: 4.66). 06/2012; 46(15):4677-86. DOI: 10.1016/j.watres.2012.06.007
Source: PubMed

ABSTRACT The effectiveness of ultraviolet (UV) combined with chlorine as a novel advanced oxidation process (AOP) for drinking water treatment was evaluated in a bench scale study by comparing the rate of trichloroethylene (TCE) decay when using UV/chlorine to the rates of decay by UV alone and UV/hydrogen peroxide (H₂O₂) at various pH values. A medium pressure mercury UV lamp was used. The UV/chlorine process was more efficient than the UV/H₂O₂ process at pH 5, but in the neutral and alkaline pH range, the UV/H₂O₂ process became more efficient. The pH effect was probably controlled by the increasing concentration of OCl⁻ at higher pH values. A mechanistic kinetic model of the UV/chlorine treatment of TCE showed good agreement with the experimental data.

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    ABSTRACT: The objective of this study was to investigate the effects of combined low-pressure ultraviolet (LPUV) irradiation and free chlorination on the formation of trichloronitromethane (TCNM) by-product from amine precursors, including a commonly used polyamine coagulant aid (poly(epichlorohydrin dimethylamine)) and simple alkylamines dimethylamine (DMA) and methylamine (MA). Results showed that TCNM formation can increase by up to 15 folds by combined UV/chlorine under disinfection to advanced oxidation conditions. The enhancement effect is influenced by UV irradiance, chlorine dose and water pH. Extended reaction time leads to the decay of TCNM by direct photolysis. The combined UV/chlorine conditions significantly promoted degradation of polyamine to generate intermediates, including DMA and MA, which are better TCNM precursors than polyamine, and also facilitated transformation of these amine precursors to TCNM. Under combined UV/chlorine, polyamine degradation was likely promoted by radical oxidation, photodecay of chlorinated polyamine and chlorine oxidation/substitution. Promoted TCNM formation from primary amine MA was primarily due to radicals' involvement. Promoted TCNM formation from secondary amine DMA likely involved a combination of radical oxidation, photo-enhanced chlorination reactions and other unknown mechanisms. Insights obtained in this study are useful for reducing TCNM formation during water treatment when both UV and chlorine will be encountered.
    Environmental Science & Technology 01/2014; · 5.48 Impact Factor

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