| Enteric diseases caused by waterborne pathogens are the third leading cause of death worldwide and outbreaks of waterborne diseases continue to occur in the United States and other developed countries. While disinfection of public water supplies with chemical oxidants has been conducted for more than 100 years, little is actually understood about the impacts that different water quality parameters can have on the inactivation behavior of microorganisms, or specific mechanisms governing microbial inactivation.; Using the CT concept first developed by Chick and Watson, with an integrated oxidant exposure, the influence that selected water quality parameters---pH, temperature, natural organic matter, and turbidity---can have on the inactivation response of Bacillus subtilis (B. subtilis) spores was investigated using monochloramine and ozone. B. subtilis spore inactivation response to ozone was compared to that of Bacillus megaterium (B. megaterium), to observe how differences in inactivation behavior could provide a better mechanistic understanding of disinfection processes. This research also investigated the ozone inactivation potential of Mycobacterium avium ( M. avium), using conventional culturing techniques and novel microscopic techniques.; Ozone and monochloramine inactivation of B. subtilis spores was significantly impacted by water quality conditions, in particular pH. The inactivation of B. subtilis spores was also impacted by initial ozone dose, which induced an extending lag phase as ozone concentrations increased. B. subtilis and B. megaterium spores have significantly different inactivation responses to ozone, regardless of their phylogenetic and physiological similarities. When compared to demand free phosphate buffered water, inactivation behavior of both of these Bacillus species was affected by dissolved and colloidal constituents in Lake Zurich water, but in different ways. The differences in inactivation behavior as a result of pH, and the effects of Lake Zurich water, indicate that inactivation responses observed in phosphate buffered waters cannot be conservatively extrapolated to natural waters. In addition, this work suggests that the disinfection response of some model microorganisms may not be suitable to describe the response of pathogenic microorganisms and their surrogates. Standard plate culturing techniques commonly used to assess microbial inactivation could not be applied to M. avium cells since ozononation immediately induced their aggregation. |
