In a series of seven column experiments, attachment of the bacteriophage PRD-1 and MS-2 to silica beads at pH's 5.0-5.5 was at least partially reversible; however, release of attached phage was slow and breakthrough curves exhibited significant tailing. Rate coefficients for attachment and detachment were on the order of lo4 and 10-6-10-4 s-l, respectively. Corresponding time scales were hours for attachment and days for detachment. The sticking efficiency ( a ) for phage attachment was near 0.01. The rate of phage release was enhanced by raising pH and introducing surface-active chemical species, illustrating the importance of chemical perturbations in promoting biocolloid transport. In a series of batch experiments, MS-2 adsorbed strongly to a hydrophobic surface, octadecyltrichlorosilane-bonded silica, a t both pH's 5 and 7. Adsorption to the unbonded silica at pH 5 was linear, but was 2.5 (with Ca2+) to 0.25% (without Ca2+) of that to the bonded surface. Neither MS-2 nor PRD-1 adsorbed to unbonded silica at pH 7. Hydrophobic effects appear to be important for adsorption of even relatively hydrophilic biocolloids. mathematical models are available for describing transport of viruses and other colloids in soil and groundwater ( l ) , all lack data for validation.The research described in this paper is part of our ongoing studies of virus attachment and transport in natural waters. Our first objective was to determine the effect of pH on the attachment of MS-2 and PRD-1 to well-characterized silica and hydrophobic surfaces. We chose MS-2, PRD-1, and silica as their surface chemical properties are well-known, offering the potential to determine the factors controlling the degree of adsorption. We examined the importance of Ca2+ concentration and temperature in influencing MS-2 adsorption on silica at one pH. A second objective was to demonstrate the reversibility of bacteriophage adsorption and to determine the effect of chemical perturbations on the rates of desorption. Our third objective was to test equilibrium, first-order, and two-site colloid transport models using the quantitative data and parameter estimates developed for the chemical conditions studied. IntroductionThe fate of viruses in groundwater is governed by attachment to immobile substrates, generally referred to as adsorption, and by inactivation (1). In a study of over 100 groundwater samples, Yates et al. (2) found temperature to be the only measured water characteristic significantly correlated with viral inactivation. Gerba (3) cited extensive evidence to the effect that sorbed viruses are generally protected from inactivation relative to free viruses.Several factors contribute to the adhesion of viruses and other colloids to soil particles, including electrostatic attraction and repulsion, van der Waals forces, covalent-ionic interactions, hydrogen bonding, and hydrophobic effects. Murray and Parks (4) showed that free energies for adsorption of poliovirus to a variety of metal oxides corresponded well with potentials predicted by electrosta...

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