SORPTION OF VIRUSES DURING FLOW-THROUGH SATURATED SAND COLUMNS

Viruses pathogenic to humans have been found in wells and drinking wat er doe to the improper placement of wastewater disposal operations (e. g., septic tanks, wastewater infiltration basins) and inadequate remov al of the organisms as the wastewater percolated through the soil. In order to develop well head protection criteria that are protective of public health, it is necessary to understand the mechanisms that contr ol virus retention and removal in porous media. In this study, we repo rt the results of a series of experiments on virus transport through s and columns (9.2 cm in diameter and 10.5 or 20 cm long) under saturate d-flow conditions. Two bacteriophages, MS-2 and phi X-174, were used i n the experiments. Virus solution was applied to the lower end of the column as a constant input, and samples were collected at the effluent end. A virus transport and fate model, partially calibrated with the transport parameters obtained from Br- tracer experiments, was used to evaluate the retention and inactivation characteristics of the viruse s. We found that, while MS-2 was not sorbed by the Ottawa sand, a sign ificant amount of the applied phi X-174 was retained but not inactivat ed in the columns. This was probably due to the difference in their is oelectric points. Retention of phi X-174 exhibited trends consistent w ith first-order attenuation that increased with residence time; howeve r, the sand was found to have a finite sorption capacity for phi X-174 . This study also demonstrates that virus sorption can be evaluated mo re effectively with a well-controlled column flow system than by the c ommonly used batch equilibration method.