AWWA JAW54208

Bench-scale experiments determined the germicidal effects of varying dosages of polychromatic ultraviolet (UV) radiation on oocysts of Cryptosporidium parvum. C. parvum oocysts suspended in treated surface water were irradiated with polychromatic light emitted by either a medium-pressure, continuous-wave UV lamp or a pulsed-UV lamp then assayed with human cell culture techniques. Experiments conducted using pulsed-UV doses of greater than or equal to 16 mJ/cm2 provided >2-log inactivation of suspended oocysts of C. parvum. Experiments at lower UV dosages established a dose-response relationship with both the medium-pressure and pulsed-UV lamps. When disinfection results from both light sources were compared on an equivalent dosage basis, no statistical difference in disinfection power was found between the medium-pressure and pulsed-UV lamps. Results from both lamps showed that UV doses as low as 7.5 and 11 mJ/cm2 provided inactivation of infectious oocysts of C. parvum at rates of 1 log (90%) and 2 log (99%), respectively. The authors also examined UV disinfection of heterotrophic bacteria and Escherichia coli. They found the response of heterotrophic bacteria to be statistically different from that of C. parvum, whereas E. coli's response to UV light did not statistically differ from that of C. parvum. This suggests that E. coli may be a surrogate organism for C. parvum disinfection provided by UV technologies. Includes 39 references, tables, figures.