Fate and transport model of Cryptosporidium

The waterborne pathogen Cryptosporidium has been identified in surface drinking water supplies. Suspected sources of this pathogen include sewage and the feces of animals, particularly dairy calves. There are many dairy cattle and significant sewage effluent discharges in the Catskill-Delaware watershed that is part of the New York City water supply system. This water supply serves 8,000,000 customers with 5.8 x [10.sup.9] L (1.5 billion gal. of water daily). This paper is concerned with the movement and fate of pathogens from waste-water and dairy sources and the resulting raw water quality for New York City. Manure and Cryptosporidium oocysts are modeled as surface pollutants and assumed to move in response to runoff events in the six watershed-reservoir systems within the Catskill-Delaware watershed. Oocyst degradation in manure and in water is modeled with first-order kinetics. Rudimentary stream routing and reservoir modeling with a first-order decay function complete the fate and transport modeling of oocysts in the watercourse. Reported effluent discharge rates and oocyst concentrations in secondary treated sewage allow estimation of wastewater-derived oocyst contributions. This research highlights the importance of wastewater-derived oocysts, the need for expanded research into oocyst fate in streams and reservoirs, and the concentration of oocysts in sewage effluent.