MODELING OF VIRUS TRANSPORT UNDER VARIABLY SATURATED CONDITION, FOCUSING ON THE EFFECT OF IONIC COMPOSITION OF AQUEOUS PHASE

Adsorption of microbial particles to the soil surfaces is an important mechanisms in removal of pathogenic microorganisms during transport through subsurface porous media. The objective of this research was to explore the mechanisms of virus removal under saturated and unsaturated conditions focusing on the effect of ionic composition of water. The transport of bacteriophages MS2 and ƒÖX174 as surrogate of pathogenic viruses in iron oxides- coated sand columns was studied under various conditions, such as different buffers, and saturation levels. Fitting of a transport model to the breakthrough curves was performed to determine the adsorption parameters. Using phosphate buffer, an insignificant retention of both phages was observed due to strong reaction of phosphate with metal oxides. The insignificant retention under unsaturated conditions implies the negligible adsorption to the air-water interfaces. In contrast, a significant retention of both phages was observed in case of utilizing bicarbonate buffer. However, the fitted breakthrough curves showed that the attachment rate of viruses to SWI decreased as feeding of virus suspension continued. Some complementary experiments revealed that the adsorption sites of SWI were gradually blocked by bicarbonate ions and the adsorption of viruses was not the reason of blocking effect. Our findings clearly show the importance of electrostatic interactions to SWI as dominant mechanism for retention of microbial colloids.