Effects of pH and hydrophobicity on the transport of viruses and bacteria in saturated media

Abstract

Effects of pH and hydrophobicity on attachment-detachment of PRD-1 and MS-2 in three different soils, and Pseudomonas fluorescens P17 and Bacillus subtils TF-32 in 0.5-mm silica beads, were investigated in laboratory-column experiments. Attachment and detachment of hydrophobic virus PRD-1 may be predominantly controlled by hydrophobic interactions in soil media, while those of less-hydrophobic virus MS-2 may be mainly controlled by pH. Bacteria tend to exhibit hydrophobic interactions, since their surface contains hydrophobic substances. Soil media can exhibit strong hydrophobic interactions as well as electrostatic interactions. Parameters for three different transport models were estimated. The equilibrium model fits to the breakthrough curves of MS-2 in Cape-Cod soil resulted in dispersion coefficients similar to those of the conservative tracer (NaCl). The first-order and two-site model parameters indicated non-equilibrium conditions in all cases. Calculations of the two-site model were less stable than the first-order model for these breakthrough curves.