Innovative Technologies for Waste Water Disinfection and Pathogen Detection

New and improved methods are needed to disinfect pathogens in treated wastewater, especially highly resistant ones like Cryptosporidium parvum oocysts. In addition, new and improved methods are needed to detect pathogens and indicators for them in wastewater in order to monitor the efficacy of disinfection and other waste water treatment processes. Spores of the anaerobic bacterium Clostridium perfringens and male-specific coliphages were evaluated as indicators of waste water treatment and chlorine disinfection. These indicators were easy to measure and were found to be more resistant to primary and secondary wastewater treatment and chlorine disinfection than were indicator bacteria such as fecal coliforms and enterococci. New cell culture methods were used to assay the infectivity of C. parvum oocysts in treated wastewater and water subjected to disinfection by electrochemically generated mixed oxidants. C. perfringens spores, coliphage MS2 and E. coli also were evaluated for their responses to mixed oxidants. Mixed oxidants effectively inactivated C. parvum oocysts in water and tertiary treated waste water, with infectivity reductions of >99.9%. C. perfringens spores were good indicators of C. parvum oocyst inactivation in water at mixed oxidant dose of 4 mg/l. In tertiary treated waste water, C. parvum oocysts were efficiently inactivated (>99.9%) by mixed oxidant doses of about 10-15 mg/l. Under the same conditions, C. perfringens spores, coliphage MS2 and E. coli were more sensitive to mixed oxidants than were C. parvum oocysts. Electrochemically generated mixed oxidants effectively inactivate C. parvum oocysts in water and treated waste water at practical doses and contact times. C. perfringens spores and male-specific coliphages are useful indicators of disinfection efficacy by mixed oxidants and chlorine, but they are not as resistant as C. parvum oocyts under some disinfection conditions.