Catalytic Oxidation of THM Precursors Using Ozone and Ultraviolet Radiation


The purpose of this study was to identify the effects of ultraviolet (UV) catalyzed ozone oxidation of trihalomethane (THM) precursors for a groundwater source. The scope of this research was to define an empirical model to predict THM precursor destruction rates and to establish the product water quality attainable by UV/Ozone processes. The experimental design consisted of a full factorial experiment for 3 applied ozone dose rates (2, 3, and 4 grams/hour (gms/hr)), 3 UV dose rates (3.11, 1.33, and 0.728 watts/liter (W/L)), and 3 pH adjustments (ambient pH, ambient pH+0.5 standard units (SU), and ambient pH-0.5 SU), resulting in a total of 27 UV/Ozone experiments. Also included were 5 half factorial experiments for ozone alone and 5 experiments for UV alone. Also included were 2 aeration control experiments. The effects of pH and temperature on THM precursor destruction rates were not shown to be significant within the levels tested (6.2-8.7 SU and 7-40°c respectively). The effects of pH may not have been significant due to the narrow pH range tested and the rapid equalization (15 minutes) of pH to approximately 8 SU for all pH adjustments. Temperature effects may have been confounded by the uv dose rate used since the temperature increased as the UV dose rate increased. UV dose rate was shown to be a significant factor for the UV/Ozone experiments. The effect of UV dose rate was, however, small when compared to applied ozone dose rate, and THM formation potential concentration (THMFP) effects. The influence of UV dose rate was, however, large when compared to ozone (no UV) experiments. Thus the influence of UV was shown to be mostly catalytic. UV/Ozone oxidation reduced THMFP concentration to levels ranging from 15 ppb too ppb for all experiments tested after a 3 hr reaction time (initial 7 day THMFP ranged from 252 ppb to 118 ppb). These reductions are sufficient to meet anticipated maximum contaminant levels (MCLs) that may drop as low as 20 ppb (1990 MCL for total THMs is 100 ppb). Ozone (no UV), UV (no ozone), and aeration were not effective processes for reducing THMFP to anticipated MCLs.


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Graduation Date





Dietz, John D.


Master of Science (M.S.)


College of Engineering


Civil and Environmental Engineering

Degree Program

Environmental Engineering




120 p.



Length of Campus-only Access


Access Status

Masters Thesis (Open Access)




Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic

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