Effects of pH, ionic strength, dissolved organic matter, and flow rate on the co-transport of MS2 bacteriophages with kaolinite in gravel aquifer media.

Viruses are often associated with colloids in wastewater and could be transported with colloids into groundwater from land disposal of human and animal effluent and sludge, causing contamination of groundwater. To investigate the role of colloids in the transport of viruses in groundwater, experiments were conducted using a 2m long column packed with heterogeneous gravel aquifer media. Bacteriophage MS2 was used as the model virus and kaolinite as the model colloid. Experimental data were analyzed using Temporal Moment Analysis and Filtration Theory. In the absence of kaolinite colloid, MS2 phage traveled slightly faster than the conservative tracer bromide (Br), with little differences observed between unfiltered and filtered MS2 phage (0.22 microm as the operational cut-off for colloid-free virus). In the presence of kaolinite colloids, MS2 phage breakthrough occurred concurrently with that of the colloidal particles and the time taken to reach the peak virus concentration was reduced, suggesting a colloid-facilitated virus transport in terms of peak-concentration time and velocity. Meanwhile mass recovery and magnitude of concentrations of the phages were significantly reduced, indicating colloid-assisted virus attenuation in terms of concentrations and mass. Decreasing the pH or increasing the ionic strength increased the level of virus attachment to the aquifer media and colloids, and virus transport became more retarded, resulting in lower peak-concentration, lower mass recovery, longer peak-concentration time, and greater apparent collision efficiency. Increasing the concentration of dissolved organic matter (DOM) or flow rate resulted in faster virus transport velocity, higher peak-concentrations and mass recoveries, and lower apparent collision efficiencies. The dual-role of colloids in transport viruses has important implications for risk analysis and remediation of virus-contaminated sites.