Impact of UV Treatment on Disinfection Byproduct Precursors and Subsequent Byproduct Formation from Chlorine and Chloramine Public Deposited

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Last Modified
  • March 21, 2019
Creator
  • Lyon, Bonnie Anne
    • Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
Abstract
  • As natural source water quality becomes increasingly impacted by anthropogenic activity, utilities are looking towards alternative disinfection techniques to meet regulations related to the delivery of quality drinking water to consumers. Ultraviolet (UV) irradiation is one process that is being used to address this issue, but there have been few comprehensive studies that have looked at the effect of UV treatment on the formation of disinfection byproducts (DBPs) and in particular, emerging DBP classes that are thought to be more geno- and cytotoxic than the regulated trihalomethanes and haloacetic acids. The objective of this research was to evaluate the impact of UV irradiation on organic and inorganic DBP precursors and the formation of a range of DBPs from subsequent addition of chlorine or chloramine. Disinfection doses of UV (40-186 mJ/cm2) followed by chlorination/chloramination had little effect on the formation of regulated trihalomethanes and haloacetic acids, but the formation of several emerging DBPs were increased by UV and chlorination/chloramination in waters containing 1-10 mg N/L nitrate (halonitromethanes and cyanogen chloride) or regardless of nitrate content (chloral hydrate). Their formation was affected to a greater extent with medium pressure (MP) compared to low pressure (LP) UV. The higher potential toxicity of these byproducts compared to the regulated DBPs warrants consideration of practices that could reduce their formation. If MP UV is being implemented on source waters containing elevated nitrate, utilities should consider options for nitrate reduction upstream from UV processes. The use of fluorescence spectroscopy allowed for the observation of changes to organic precursor components following combinations of UV, chlorine, and chloramine treatment that were not detectable by UV/visible absorbance spectroscopy or dissolved organic carbon analysis. Results of an in vitro cytotoxicity assay employing human colon cells showed that concentrated waters treated with MP UV followed by chloramination had a higher cytotoxicity than those treated with only chloramine, suggesting that further research is needed to evaluate the effect of byproduct mixtures produced during UV-chloramine treatment. The findings of this research have implications for the design and optimization of combined UV-chlorine/chloramine processes for drinking water treatment.
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  • In Copyright
Advisor
  • Weinberg, Howard
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill
Graduation year
  • 2012
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