The inactivation kinetics of Cryptosporidium parvum in sequential disinfection treatment strategies using ozone, hypochlorous acid and monochloramine

The objective of this research was to investigate the kinetics of Cryptosporidium parvum oocyst inactivation with ozone, hypochlorous acid, and monochloramine in order to determine the effectiveness of the disinfectants in treatment strategies employed by drinking water utilities. Additional experiments were performed in order to provide insight into the mechanism of C. parvum inactivation.; A modified in vitro excystation viability assay, shown to be consistent with infectivity for chemical disinfection, was utilized to investigate the kinetics of C. parvum inactivation with ozone followed by hypochlorous acid or monochloramine. The data obtained revealed significant enhancements in the rate of inactivation with free or combined chlorine after ozone pretreatment.; Experiments investigating the causes of the enhancements were performed using various combinations of disinfectants in series. The results of these experiments provided evidence that ozone, hypochlorous acid and monochloramine react with similar constituents in the oocyst wall. However, only ozone pretreatment resulted in rates of secondary inactivation enhancement that appear to be limited by a mass transfer process.