The results from this study show how different precursors affect halonitromethane (HNM) formation as well as how different free chlorine doses can affect HNM speciation. This study shows that the low pressure ultraviolet (LPUV) and free chlorine concurrent exposure can enhance HNM formation. In addition, most previous studies in the literature showed trichloronitromethane (TCNM) forming in greater quantities followed by monochloronitromethane (MCNM) and dichloronitromethane (DCNM). However, the results of this study show that, in deionized (DI) water matrices, MCNM forms in greater quantities at chlorine to nitrogen (Cl:N) ratios less than 3, while TCNM forms in greater quantities at Cl:N ratios greater than 3. Even so, the increase in TCNM formation did not increase linearly as the Cl:N ratio increased; there was a decreased rate of return when Cl:N ratios were greater than 3. The type of nitrogenous precursors can affect the amount of HNMs formed, with glycine forming a higher amount of total HNMs compared to methylamine (MA) and dimethylamine (DMA). The source of water can also affect which HNM species is formed in greater concentrations. The limited number of real water samples showed that the river waters have higher than normal total organic carbon (TOC) and dissolved organic nitrogen (DON), which are associated with greater nitrogenous precursors and higher HNM formation. Each water source can have different nitrogenous precursors; river waters may have more algal organic matter while wastewater would have higher organic matter and synthetic chemicals. In addition, source waters can have different constituents, such as varying dissolved oxygen (DO) levels and inorganic ions, which might inhibit HNM formation or affect specification.

This research involved an investigation of the application and reaction mechanisms of UV/H₂O₂ for the simultaneous removal of regulated halogenated disinfection byproducts (DBPs) and odorous aldehydic algal byproducts in the presence of geosmin and 2-methylisoborneol, which are earthy-musty odorants that commonly occur in drinking water. UV/H₂O₂ is an expensive advanced oxidation process that is used to successfully control geosmin and 2-methylisoborneol. The aqueous oxidation of odorous aldehydes and halogenated DPBs were compared to that of the earthy-musty odorants and the changes to the sensory properties of the drinking water were examined. Geosmin, 2-methylisoborneol, heptadienal, decadienal, and nonadienal, hexanal, and the two most prevalent classes of DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were oxidized by UV photolysis alone and the UV/H₂O₂ process with 6 mg/L H₂O₂ and realistic ng/l to μg/L concentrations of the test compounds. The di-, and tri-brominated THMs and HAAs were substantially (80-99%) removed by direct UV photolysis mechanism at the same UV/H₂O₂ dose required for removing 95% of geosmin and 65% of 2-methylisoborneol with faster reaction rates for the more bromine substituted compounds. The C-Br bond cleavage is the first step of brominated HAAs degradation by UV photolysis, and followed by either of two second steps: reaction with oxygen producing peroxyl radical or interaction with water molecule causing O-H insertion/H-Br elimination. Trichloromethane and mono-, di-, and tri-chlorinated HAAs were not substantially removed under the same conditions used for the brominated compounds. The principal removal mechanism was by the reaction with hydroxyl radical for the UV/H₂O₂ process. The second order reaction rate constants were on the order of 10⁶ - 10⁸ M⁻¹ s⁻¹ with faster reaction rates for the less chlorine substituted compounds. Based on the reaction rates, hydrogen and halogen ion balance, and isotope effect, both hydrogen abstraction and electron transfer reaction were involved in the first steps of the chlorinated HAA degradation. Three odorous aldehydes - heptadienal, decadienal, and nonadienal - were removed faster than geosmin or 2-methylisoborneol, and direct UV photolysis was the principal reaction mechanism for the removal of these unsaturated aldehydes. Hexanal was poorly removed. In sensory tests, new odors such as sweet or chalky odors were produced while the concentration and initial odor intensity of these fishy/grassy-smelling aldehydes were reduced with increasing exposure time to UV/H₂O₂. Carbonyl compounds were detected as products of the UV photolysis of nonadienal. These carbonyls were not removed by further UV irradiation, which was thought to be partially related with production of new odors. The results indicate that the UV/H₂O₂ is effective to control both odorous compounds and brominated DBPs. This process can be seasonally applied to control both contaminants especially, in the warm summer when both odorants and DBPs have their higher concentrations. Removal of brominated DBPs can be a significant addition to water utilities that have difficulty in meeting regulatory levels for these highly toxic compounds. The result on the removal of odorous aldehydes indicate that new types of odors were produced from the oxidation of odorous aldehydes suggesting sensory test coupled with chemical analysis should be considered in designing oxidation process to control recalcitrant odorants. / Ph. D.

No description available.

La désinfection de l’eau de piscine est essentielle pour prévenir la propagation de maladies infectieuses. Cependant, les désinfectants réagissent avec les composés organiques présents dans l’eau y compris ceux introduits par les baigneurs, tels que les fluides corporels et les crèmes solaires, conduisant à la formation de sous-produits de désinfection (SPD) associés à des effets néfastes sur la santé. Le devenir des filtres UV organiques, présents dans les crèmes solaires et les produits de soins personnels, dans les piscines d'eau de mer chlorées est peu connu. Les objectifs de la présente étude étaient d'étudier la réactivité des filtres UV organiques dans l'eau de mer chlorée, d’identifier les SPD générées par les filtres UV, d'analyser l’occurrence des SPD dans les piscines d'eau de mer, et d'examiner leur génotoxicité. Des expériences de chloration ont été menées dans l'eau de mer reconstituée sur cinq filtres UV couramment utilisés : l’oxybenzone (OXY), le dioxybenzone (DIOXY), l’avobenzone (AVO), l’octyl méthoxycinnamate (OMC), et l’octocrylène (OC). Tous les composés étudiés sauf l’OC ont été dégradés conduisant à la formation de SPD bromés pour lesquels des schémas réactionnels ont été proposés. L'occurrence de ces SPD a été étudiée dans les piscines d'eau de mer où des SPD bromés ont été quantifiés. La génotoxicité de l’hydrate de bromal (BH), l’un des SPD généré par OXY et DIOXY et détecté dans les piscines d'eau de mer, a été évaluée. BH a induit une activité génotoxique dans le test d'Ames et l'essai de comète. Cette étude montre que les filtres UV peuvent agir comme précurseurs pour la formation de SPD génotoxiques dans l’eau de mer chlorée. / Disinfection of swimming pool water is critical to prevent outbreaks of infectious diseases. However, disinfectants react with organic compounds present in water, including anthropogenic inputs (e.g. body fluids, sunscreens), leading to the formation of disinfection byproducts (DBPs) that have been linked to adverse health effects. Little is known about the fate of organic UV filters, present in sunscreens and personal care products, when introduced into chlorinated seawater swimming pools. The aims of the present study were to investigate the reactivity of five commonly used organic UV filters in chlorinated seawater, identify DBPs generated from the UV filters, analyze the occurrence of these DBPs in seawater swimming pools, and examine their genotoxicity. Chlorination experiments were conducted to analyze the reactivity of the UV filters oxybenzone (OXY), dioxybenzone (DIOXY), avobenzone (AVO), octyl methoxycinnamate (OMC), and octocrylene (OC) in reconstituted seawater. All the studied UV filters except OC were degraded in chlorinated seawater resulting in the formation of brominated DBPs. Based on the identified byproducts, transformation pathways were proposed. The occurrence of the identified DBPs was investigated in seawater pools. Several brominated DBPs were identified in seawater pool samples. The genotoxicity of bromal hydrate (BH), which was generated by the benzophenone UV filters OXY and DIOXY and detected in the investigated seawater pools, was assessed. BH induced genotoxic activity in the Ames test and in the comet assay. Overall, this study shows that UV filters can act as precursors for the formation of genotoxic DBPs in chlorinated seawater pools.