Study On Viruses Transportation Through Saturated Porous Media Under Managed Groundwater Recharge Condition

Groundwater is an important part of water resources. In order to solve the increasingly serious contradiction between supply and demand of water resources, the water resources utilization is transferred to the remediation of contaminated aquifer and repeated recycling of water resources. The water treatment of pathogenic microorganisms has become a very difficult problem to solve in the situation. Viruses are the most threatening ones of the microorganism in groundwater. Viruses are smaller than others and have higher infectivity. Therefore, virus can travel through a much wider range of pore networks in aquifer media compared with bacteria and protozoa the in porous media. As bacterial viruses, bacteriophages could infect and lysis host bacteria, are used as indicative microorganisms in the monitoring of Escherichia coli in water. Bacteriophages with low risk to infect human are easier to be detected through simple equipment, so bacteriophages usually are considered as an indicator of enteroviruses. Therefore, this study choose Escherichia coli phage as representative one of ground water viruses. We investigated the transportation of viruses under different hydrodynamic conditions and different water chemistry conditions. We hope the result could provide necessary theoretical basis and technical support to protect the groundwater environment.Based on the research before, pH(acidic / neutral / alkaline), ionic strength(IS=0.01 M, 0.05 M), ion species(Ca2+/Na+/ phosphate buffer solution), natural colloids, media type(glass bead / sand medium) and hydrodynamic conditions(0.17ml/min 0.34ml/min) were selected as the main factor to investigate the deposition, release and other environmental behavior in water saturated media. The data obtained from lab experiment were treat as basic data to model virus’ transportation in water saturated media through COMSOL Multiphysics software. The model to describe viruses’ convection, dispersion, deposition and release was carried out previously. The transportation of viruses in water saturated media was quantitatively described via the model. The modeling result provide basic data for prediction viruses’ migration in aquifer.Lab experimental results show:1. The effects of water chemistry and hydrodynamic conditions on the migration of virus: The increase of H+, will reduce the virus colloidal DLVO barrier, thus increasing the adsorption of virus colloidal; with increase of phosphate buffer concentration, the suspension stability and migration ability of viruses are both increasing; ether Na+ or Ca2+ format negative condition for viruses’ migration. Changes in pH and ionic strength have an important effect on the migration of viruses in the aquifer media. But the change of ionic strength is more important than the change of pH. At the same condition, Ca2+ has a greater impact on the transportation of viruses; In the presence of natural colloids, the stability of viruses’ colloidal suspensions can be improved obviously, and the migration of virus colloids can be promoted effectively. Strong hydrodynamic condition can increase the penetration rate of viruses’ colloid, increase the release of virus, and reduce the retention of the virus in the aquifer medium. As the flow rate increases, the rotational torque of the virus particles increases, which makes the virus particles not easy to adsorb and easier to released. Under the condition of low flow velocity, the viruses’ particles are stuck in the medium for a long time, the number of collisions between the virus particles and the medium particles increases, and the amount of the viruses absorbed increase.2 The effect of aquifer media on virus migration Compared with glass beads, quartz sand surface is very rough. In colloidal scale, the rough surface form local favorable conditions of adsorption easily. At the same time, lower surface potential of quartz sand resulting in larger absorption than glass beads’. Influenced by the irregular shape of quartz sand, medium pore in san aquifer is not uniform. Thus, viruses’ colloidal particles do not travel through the small pores. Compared with glass bead medium, migration pathway of viruses becomes shorter, resulting in the faster migration speed.Through the simulation of viruses Migration Experiment:1. The effect of Ca2+ on the rate constant of bio colloid deposition was greatest. The increase of flow rate can lead to the increase of the adsorption rate constant of bio colloid. Velocity increases, the single collector collection efficiency decreases, and adhesion efficiency increase, as the flow rate increase will lead to a shorter residence time of the bio colloid in porous media, and solid phase collector occur collision of colloidal quantities also becomes less. At the same time, flow velocity increased bio colloidal shear force, bio colloidal will with water even with the roll out of adsorption, which lead to increased release of virus, thus contributing to the high velocity under the condition of bio colloidal mass recovery rate is extremely high. The effect of the medium on the deposition rate constant is not very large, which is related to the hypothesis condition of the colloid filtration theory.2. In great bio colloidal adsorption conditions, the calculation result of the deposition rate constant with the simulation results is different, in high concentration of Ca2+ and, under the condition of low pH calculation result is less than the simulation results more than four times, which in practice should be paid attention to it.