Cryptosporidium Occurrence in Wastewaters and Control Using UV Disinfection

This paper summarizes the conclusions of two recently completed projects that examined the occurrence of the protozoan pathogen Cryptosporidium in wastewater streams, and the efficacy of ultraviolet (UV) light for treatment of wastewaters to control Cryptosporidium. A 15-month survey of Cryptosporidium oocyst occurrence was conducted at ten US wastewater treatment plants. Cryptosporidium oocysts were found in all wastewater matrices from raw sewage to tertiary effluents. However, low doses of UV radiation (3 mJ/cm2) from either low or medium pressure UV lamps were effective in achieving an inactivation level of greater than three logs for Cryptosporidium oocysts in wastewater effluent as measured by cell culture. No evidence of oocyst DNA repair was observed. While the occurrence of Cryptosporidium oocysts is common in wastewater effluents, UV is highly effective for oocyst inactivation in wastewater.