AWWA PATH50791

Major sources of Cryptosporidium parvum in watersheds include domestic livestock operations and human activities. The objective of this research was to establish a framework for defining and quantifying Cryptosporidium source terms in watersheds, and to use it to compare the relative contributions of cattle farms and wastewater treatment plants. The oocyst production rate from each source was estimated using epidemiological, veterinary and medical data from the literature. The relative significance of the oocyst production rates was evaluated for a hypothetical watershed using statistical analysis. The analyses indicated that young calves make the greatest contribution to oocyst production from cattle farms, due to their high positive rate and oocyst shedding rate. Thus for a cattle farm, calving periods become much more critical than non-calving periods. The influence of farms on watershed Cryptosporidium oocyst loads is more significant during wet weather due to the runoff of manure applied to the cultivated land and from farm pastures. The influence of wastewater treatment plant effluents to watershed Cryptosporidium oocyst loads is more significant during dry weather when runoff is absent and the flow rate of the receiving river is low. Includes 31 references, tables, figure.