Transport of Cryptosporidium parvum oocysts through saturated columns

Transport of Cryptosporidium parvum oocysts through three substrates was used to determine dispersion, retardation, and first-order decay parameters for the convective dispersion equation (CDE). Pulses of diluted Holstein calf feces containing oocysts were passed through saturated columns parked with either glass beads, coarse sand, or shale aggregate. Effluent chloride breakthrough curves (BTCs) were used to fit pore water velocities and dispersions for each column to the CDE. These pore water velocities were then used to fit dispersion, retardation and first-order decay factors to the CDE for C. parvum oocyst BTCs for each column. Dispersion coefficients for oocysts averaged 0.8 cm(2) s(-1) in glass beads, 1.7 cm(2) s(-1) in sand, and 1.3 cm(2) s(-1) in shale aggregate. The ratio of oocyst dispersion to chloride dispersion was <1 for all substrates, suggesting oocysts experienced less sheer and turbulence than the pore water. Diffusivities of 0.07 cm for glass beads, 0.15 cm for sand, and 0.09 cm for shale aggregate show that facilitated transport in sand was greater than in the other two substrates. Retardation coefficients for oocysts averaged 1.0 in glass beads and sand and 0.9 in shale aggregate, indicating oocysts did not adhere to these substrates. First-order decay coefficients of 0.5 s(-1) for glass beads, 0.8 s(-1) for sand, and 0.6 s(-1) for shale aggregate indicate significantly higher removal rates in the sand columns. These data suggest oocysts may travel significant distances in both subsurface and overland flow.