| The application of ozone as a disinfectant has been gaining popularity because of its potential to treat pathogens such as Cryptosporidium parvum (C. parvum), a protozoan parasite that has shown strong resistance to common water disinfectants such as free chlorine and monochloramine. However, process design and operating conditions for high levels of C. parvum inactivation often result in the generation of other types of DBPs of public health concern. One of such DBPs is bromate, a known human carcinogen which is likely to form during ozonation of bromide-containing waters.; Therefore, process optimization with the goal of adequate inactivation of pathogens, such as C. parvum, with minimum production of undesirable DBPs, such as bromate, has been a primary challenge for the application of ozone in drinking water disinfection. There have been numerous studies published that have focused on improving the understanding of both the inactivation kinetics of C. parvum oocysts with ozone and the mechanisms responsible for bromate formation. Computer modeling has often been employed to predict the ozone-induced formation of bromate, in particular, because of its mathematical complexity. However, past studies have been confined to lab-scale ozone contactors with close to ideal hydrodynamic conditions. Moreover, an integrated approach with a goal of simultaneous control of microorganism inactivation and DBP formation has seldom been attempted.; The primary objective of this research was to develop process operation and design recommendations for the simultaneous control of C. parvum oocysts and bromate during ozone disinfection. Elucidation of factors affecting the level of C. parvum inactivation and bromate formation, such as source water characteristics and ozone contactor operating conditions, was pursued by computer simulation along with a wide range of experiments with lab- and pilot-scale ozone contactors. The effect of the presence of natural organic matter (NOM) was incorporated into the model using grouped empirical reactions between NOM and oxidants. Finally, a user-friendly software was developed to serve as a tool for engineers involved in the design and operation of ozone disinfection systems, plant operators responsible for optimizing system operation and demonstrating regulatory compliance, and government officials in charge of developing drinking water regulations. |
