Fig. 1. Plots of observed and simulated Cryptosporidium oocyst effluent concentration curves in the (a) 710-µm, (b) 360-µm, and (c) 150-µm sands. Here relative effluent concentrations (C C_i^–1) are plotted as a function of pore volumes. Simulations considered attachment (Model-Att), attachment and detachment (Model-Att/Det), straining (Model-Str), and attachment, detachment, and straining (Model-Att/Det/Str). Corresponding spatial distributions of the retained oocysts in these sands are shown in Fig. 2. Fitted model parameters are presented in Table 2.