For each of the four pilot studies, initial pilot testing was conducted to identify treatment conditions which simulated either existing or planned full-scale treatment conditions, or to identify treatment conditions optimum for turbidity and particle removal. Once the treatment conditions for seeded filter runs were selected, a series of control experiments (no chemical addition, no filter media) was conducted at each of the four pilot plants in order to determine losses of organisms, turbidity and particles through the pilot plant processes due to factors such as sedimentation or adherence to basin walls. Further, some seeded filter runs were conducted without chemical addition but with filter media in place, in order to evaluate the importance of pretreatment chemical addition on removal of organisms, turbidity and particles. Following the control experiments, seeded filter runs were conducted at each of the four pilot plants. Three replicate experiments were conducted for each control experiment and seeded filter run. An immunofluorescence assay (IFA) technique was used to enumerate Cryptosporidium parvum oocysts and Giardia muris cysts. A continuous feed method was used to add the organisms into the raw water at each pilot plant. Continuous organism feed provided the ability to sample the filter effluent during the maturation, stable operation and breakthrough phases of the filter run.