Date of Award
Master of Science (MS)
Civil and Environmental Engineering
Two novel, sustainable UV-LED advanced oxidation processes (AOPs) were evaluated for their ability to improve inactivation efficacy of P22 bacteriophage and E. coli bacteria. The first objective of this research was to determine the treatment efficacy of P22 bacteriophage and E. coli bacteria using UV-LED at wavelengths of 255, 265, and 285 nm. The UV-LED system demonstrated high inactivation potential for both contaminants at all wavelengths, suggesting it could be a potential alternative to typical low-pressure and medium-pressure mercury-based UV systems. Increased inactivation of both microorganisms was observed with decreasing wavelength (255>265>285 nm). As the peak UV absorbance for DNA occurs at approximately 254 nm, inactivation at other wavelengths was likely the result of amino acid damage in protein structures. The second objective of this research was to determine the treatment efficacy of P22 bacteriophage and E. coli bacteria using a system combining ultraviolet irradiation with hydrogen peroxide and waste slag (UV/waste slag/H2O2). The slag was a waste product of steel manufacturing with a heavy iron component, targeting Fenton-type reactions. It was hypothesized that this novel AOP would improve inactivation of both contaminants through the production of highly reactive hydroxyl radicals. The data supported this hypothesis, with significant improvements in P22 and E. coli inactivation using the UV/waste slag/H2O2 system in comparison to UV-LED alone. Scavenger experiments suggest that hydroxyl radicals were responsible for increased rates of inactivation. The final objective of this research was to determine the treatment efficacy of P22 bacteriophage and E. coli bacteria using riboflavin and UV-LEDs. Riboflavin is a photosensitizer that was used to target generation of highly reactive singlet oxygen, which was hypothesized to improve inactivation. However, the UV/riboflavin system did not demonstrate a significant improvement over the baseline UV-LED system, and even demonstrated a significant inhibition in some cases, likely due to the range of wavelengths being in the UVC region, as opposed to the higher UVA region which has shown effectiveness in producing these radicals, as well as a severe tinting of the water likely affecting UV absorbance.
Available for download on Friday, November 13, 2020