DEPOSITION KINETICS OF 2 VIRUSES IN PACKED BEDS OF QUARTZ GRANULAR MEDIA

The removal of waterborne viruses by packed bed filtration was examine d using a model system consisting of two different bacteriophages (MS2 and lambda) and saturated beds of ultrapure quartz grains. The majori ty of these experiments were conducted at a solution pH of 5, where th e viruses and quartz possess a net negative surface charge. On the bas is of a simple model that correctly predicts the isoelectric point (pI ) of MS2, the surface charge on this virus appears to originate from t he ionization of amino acid residues located on the exterior of the vi rus particle. The deposition rates of both MS2 and lambda at pH 5 are sensitive to the ionic composition of the suspending fluid, with more rapid filtration occurring at the higher salt concentrations, The filt ration rate of lambda approaches the theoretical value estimated using the Smoluchowski-Levich (S-L) approximation at pH 5 and high salt con centrations (300 mM NaCl) or at the pi of the virus, suggesting that e lectrostatic repulsive forces effectively dominate the filtration dyna mics of lambda. The filtration rate of MS2, on the other hand, is at l east 800% less than the theoretical S-L value at high salt or at the p i of this virus, suggesting that both electrostatic and nonelectrostat ic repulsive forces influence the filtration of MS2. We investigate th e possibility that this nonelectrostatic force is steric in nature, ar ising from hydrophilic polypeptide loops which extend a maximum of 1 n m off the MS2 surface.