| Current research has shown that ultraviolet (UV) light may be effective against the waterborne pathogens, Cryptosporidium parvum and Giardia spp., but issues surrounding the effects of turbidity are largely undefined. The impact of turbidity on ultraviolet inactivation of Cryptosporidium parvum oocysts and Giardia muris cysts was studied in samples of unfiltered lake water. Using a modified collimated beam exposure method, parasite suspensions with turbidities ranging from 0.25 to 20.0 NTU were exposed to controlled UV doses of 5 and 40 mJ/cm 2 from a medium pressure lamp at bench-scale. Inactivation of parasites was measured using established mouse infectivity models. Mean inactivation of C. parvum and G. muris decreased by 0.8 log-unit and 0.4 log-unit, respectively, when turbidity was increased from 0.25 to 20.0 NTU at the UV doses investigated. This turbidity effect was statistically significant at the 95% confidence level for C. parvum oocysts but was marginally insignificant for G. muris cysts. |
