Modeling colloid transport in saturated porous media : an assessment of the importance of pH and kinetics in virus transport

Abstract

Virus sorption and transport were investigated in controlled laboratory column experiments. Bacteriophage PRD1 did not sorb to silica beads at pH 7 but sorbed strongly at pH 5.5. Kinetic nonequilibrium prevailed at pH 5.5. Desorption of phage was detected during 27 pore volumes of desorption under steady-state conditions and during 135 pore volumes of desorption under transient conditions. Long tailing in the desorption limbs of the breakthrough curves suggests slow desorption rates. Advection-dispersion modeling of the experimental results with a pseudo-first-order reversible-sorption model provided a means by which to estimate transport parameters. Modeling results suggest that the pseudo-first-order rate coefficient for desorption of PRD1 from silica beads at pH 5.5 lies between 2.5 x 10⁻⁷ s⁻¹ and 6.7 x 10⁻⁶ s⁻¹ . Desorption was strongly pH dependent, and sorbed phage were eluted by raising solution pH. Column effluent concentrations of over fourteen times original input concentrations were measured during desorption at elevated pH, suggesting that significant chemical perturbations can in some instances contribute more to colloid desorption than desorption rates applied over long periods of time in steady-state systems.