Title page for ETD etd-12192004-122018


Type of Document Master's Thesis
Author Greyshock, Aimee E.
URN etd-12192004-122018
Title Evaluation of Triclosan Reactivity in Monochloraminated Waters
Degree Master of Science
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Vikesland, Peter J. Committee Chair
Edwards, Marc A. Committee Member
Love, Nancy G. Committee Member
Keywords
  • Disinfection By-Products
  • Drinking Water
  • Monochloramine
  • Triclosan
Date of Defense 2004-10-19
Availability unrestricted
Abstract
The antibacterial agent, triclosan, is widely used in many household personal care products, and it has recently been detected in wastewater treatment plant effluents and in source waters used for drinking water supply. Accordingly, the reactivity of triclosan with the disinfectants used in wastewater treatment and in the production of potable water is of interest. Monochloramine is used as an alternative disinfectant in drinking water treatment to minimize production of regulated disinfection by-products. This study examined the reactions between triclosan and monochloramine and involved analysis of monochloramine and triclosan decay and product formation under drinking water treatment conditions over a pH range of 6.5 to 10.5. Monochloramine decay in the presence of triclosan was measured relative to monochloramine auto-decomposition in the absence of triclosan using UV-VIS spectrophotometry. Experimental results showed that the monochloramine auto-decomposition intermediates, free chlorine and dichloramine, are responsible for a majority of the observed triclosan decay and product formation. A kinetic model for monochloramine auto-decomposition was modified to include terms and rate coefficients for the reactions of triclosan with monochloramine (k = 90.4 M-1h-1), free chlorine (k = 1.94×107 M-1h-1), and dichloramine (k = 2×105 M-1h-1), and was able to predict triclosan and monochloramine decay. It was determined that the reactions of dichloramine and free chlorine with triclosan were 103 and 105 times faster, respectively, than the reaction of monochloramine with triclosan. The products of these reactions, detected using GC-MS, included three chlorinated triclosan intermediates, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Low levels of chloroform were detected at pH values of 6.5 and 7.5.
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