Modeling virus transport and removal during storage and recovery in heterogeneous aquifers

Authors: TORKZABAN, SAEED - Geological Survey Of Victoria; HOCKING, MARK - Geological Survey Of Victoria; Bradford, Scott; TAZEHKAND, SHIVA - Flinders University; SASIDHARAN, SALINI - University Of California - Cooperative Extension Service; SIMUNEK, JIRI - University Of California

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2019
Publication Date: 8/27/2019
Citation: Torkzaban, S., Hocking, M., Bradford, S.A., Tazehkand, S.S., Sasidharan, S., Šimunek, J. 2019. Modeling virus transport and removal during storage and recovery in heterogeneous aquifers. Journal of Hydrology. 578. https://doi.org/10.1016/j.jhydrol.2019.124082.
DOI: https://doi.org/10.1016/j.jhydrol.2019.124082

Interpretive Summary: Aquifer storage and recovery (ASR) has been used to purposely inject rainwater, stormwater, reclaimed water, or water from other aquifers into a selected aquifer for storage, in situ treatment, and later recovery. However, the presence of microbial pathogens in ASR water poses a risk to human health if soil treatment is adequate, and expensive post-treatments may be therefore be necessary. A modeling study was conducted to systematically study factors that influence soil treatment of viruses during ASR. Virus retention and inactivation, and variability in soil properties were demonstrated to have a large influence on virus concentrations during ASR. This study provides valuable insight on the best management of ASR to optimize the removal of viruses and to minimize costs associated with post-treatment. This information should be of great interest to public health officials, government regulators, and field practitioners of ASR.

Technical Abstract: A quantitative understanding of virus removal during aquifer storage and recovery (ASR) in physically and geochemically heterogeneous aquifers is needed to accurately assess human health risks from viral infections. A two-dimensional axisymmetric numerical model incorporating processes of virus attachment, detachment, and inactivation in aqueous and solid phases was developed to systematically evaluate the virus removal performance of ASR schemes. Physical heterogeneity was considered as either layered or randomly distributed hydraulic conductivities (with selected variance and horizontal correlation length). Geochemical heterogeneity in the aquifer was accounted for using Colloid Filtration Theory to predict the spatial distribution of attachment rate coefficient. Simulation results demonstrate that the combined effects of aquifer physical heterogeneity and spatial variability of attachment rate resulted in higher virus concentrations in the recovered water at the ASR well (i.e. reduced virus removal). While the sticking efficiency of viruses to aquifer sediments was found to significantly influence virus concentration in the recovered water, the solid phase inactivation under realistic field conditions combined with the duration of storage phase had a predominant influence on the overall virus removal. The relative importance of physical heterogeneity increased under physicochemical conditions that reduced virus removal (e.g. lower value of sticking efficiency or solid phase inactivation rate). This study provides valuable insight on site selection of ASR projects and an approach to optimize ASR operational parameters (e.g. storage time) for virus removal and to minimize costs associated with post-recovery treatment.