Grantee Research Project Results
Final Report: Virus Attachment, Release, and Inactivation During Groundwater Transport
EPA Grant Number: R826179Title: Virus Attachment, Release, and Inactivation During Groundwater Transport
Investigators: Ryan, Joseph N. , Harvey, Ronald W. , Elimelech, Menachem
Institution: University of Colorado at Boulder , United States Geological Survey , University of California - Los Angeles
EPA Project Officer: Aja, Hayley
Project Period: January 13, 1998 through January 12, 2001 (Extended to January 12, 2002)
Project Amount: $372,392
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Air , Safer Chemicals
Objective:
The research outlined in this proposal will assist the U.S. Environmental Protection Agency in better understanding the processes controlling virus transport in groundwater. The following hypotheses are being addressed in this research:
· Organic matter will enhance virus transport in aquifers by adsorbing to positively charged grain surfaces and occupying these favorable attachment sites.
· The reversibility of virus attachment to aquifer sediments is controlled by heterogeneity of aquifer grains and virus interactions with different mineral and organic matter surfaces.
· The transport of viruses during long-term release will be enhanced by the blocking of favorable attachment sites by attached viruses.
· The inactivation of viruses in groundwater is accelerated by strong, irreversible attachment, but not by weak, reversible attachment. These hypotheses are being tested by research outlined in the four tasks listed below.
Summary/Accomplishments (Outputs/Outcomes):
Task 1: Virus Attachment and Release
Field and flow-through column experiments to examine the effect of organic matter on virus attachment and release are being conducted. The field experiments compared the transport of bacteriophage PRD1 to that of silica colloids. The laboratory experiments are being conducted to answer questions raised by the field experiments.
In the field experiment, bacteriophage PRD1 and silica colloids were coinjected
into
sewage-contaminated and uncontaminated zones of an iron oxide-coated sand aquifer
in Cape Cod, MA, and their transport was monitored over distances up to 6 meters
in three arrays. After deposition, three different chemical perturbations (elevated
pH, anionic surfactant, and reductant) mobilized the attached PRD1 and silica
colloids. PRD1 and silica colloids experienced less attenuation in the contaminated
zone, where adsorbed organic matter and phosphate may be hindering attachment
of PRD1 and silica colloids to the iron oxide coatings. The PRD1 collision
efficiencies are consistent with the collision efficiencies predicted by assuming
favorable PRD1 deposition on iron oxide coatings for which the surface area
coverage was measured by microprobe analysis of sediment thin sections. Zeta
potentials of the PRD1, silica colloids, and aquifer grains corroborated the
transport results, indicating that electrostatic forces dominated the attachment
of PRD1 and silica colloids. Elevated pH was the chemical perturbation most
effective at mobilizing the attached PRD1 and silica colloids. Elevated surfactant
concentration mobilized the attached PRD1 and silica colloids more effectively
in the contaminated zone than in the uncontaminated zone.
The laboratory experiments focus on the following variables:
· Size of porous media grains (experiments are complete).
·
Surface coating (experiments are complete).
·
Amount of ferric oxyhydroxide.
·
Type of virus (virus isoelectric point) (experiments are in progress).
·
Type and amount of organic matter (various surfactants, two natural organic
matter isolates, and sewage-derived organic matter).
The completed experiments on the effect of porous media grain size and ferric oxyhydroxide coating amount are being used to analyze the results of the intermediate-scale tank experiment described below (Task 3). Transport parameters for these experiments are being evaluated with the virus transport model described in Task 4. This work will culminate in the coming year with the anticipated submission of two journal articles.
Task 2: Virus Inactivation on Mineral Surfaces
Laboratory experiments were conducted to test inactivation of viruses attached to mineral surfaces. These laboratory experiments were motivated by the results of recent virus transport field experiments conducted by our research group.
In the natural-gradient transport field experiment, bacteriophage PRD1, radiolabeled with 32P, was injected into a ferric oxyhydroxide-coated sand aquifer with bromide and linear alkylbenzene sulfonates. In an aquifer zone, contaminated by secondary sewage infiltration, small fractions of infective and 32P-labeled PRD1 broke through with the bromide tracer, followed by the slow release of 84 percent of the 32P activity and only 0.011 percent of the infective PRD1.
In the laboratory experiments, the inactivation of PRD1, labeled with 35S
(protein capsid), and MS2, dual-radiolabeled with 35S (protein capsid) and
32P (nucleic acid), was monitored in the presence of groundwater and sediment
from the contaminated zone of the field site. Release of infective viruses
decreased at a much faster rate than release of the radiolabels, indicating
that attached viruses were undergoing surface inactivation. Disparities between
32P and 35S release suggest that the inactivated viruses were released in a
disintegrated state. Comparison of estimated solution and surface inactivation
rates indicate solution inactivation is about three times as fast as surface
inactivation. The actual rate of surface inactivation may be substantially
underestimated, owing to slow release of inactivated viruses.
Task 3: Virus Transport in Continuous Injections
Virus transport experiments were conducted in a two-dimensional intermediate-scale aquifer tank under physically and geochemically heterogeneous conditions to examine the effects of continuous injection and porous media heterogeneities on virus transport and to provide data to test the two-dimensional virus transport model (Task 4).
The aquifer tank experiments included layered heterogeneities consisting of porous media of different grain size and different amounts of ferric oxyhydroxide coating. Results of these experiments are being analyzed by the virus transport model.
Task 4: Virus Transport Model Development
A two-dimensional virus transport model that incorporates physically and geochemically heterogeneous porous media, deposition dynamics adding appropriate terms for inactivation (both in the aqueous and attached phases) was developed and tested for parameter sensitivity. This model and a set of virus transport calculation results appeared in the Journal of Contaminant Hydrology.
The model involves the solution to the advection-dispersion equation with terms accounting for virus inactivation in the solution and virus removal at the solid matrix surface due to attachment (deposition), release, and inactivation. Two surface inactivation models for the fate of attached inactive viruses and their subsequent role on virus attachment and release were considered. The upstream weighted multiple cell balance method was employed to numerically solve the governing equations of groundwater flow and virus transport.
Geochemical heterogeneity, portrayed as patches of positively charged metal oxyhydroxide coatings on collector grain surfaces, and physical heterogeneity, portrayed as spatial variability of hydraulic conductivity (variation of porous media grain size), were incorporated in the model. Both layered and randomly (log-normally) distributed physical and geochemical heterogeneities were considered.
Model predictions show that the presence of subsurface layered geochemical and physical heterogeneity results in preferential flow paths, and thus significantly affects virus mobility. Random distributions of physical and geochemical heterogeneity also have notable influence on the virus transport behavior. Although the solution inactivation rate was found to significantly influence the virus transport behavior, surface inactivation under realistic field conditions has a negligible influence on the overall virus transport. It was further demonstrated that large virus release rates result in extended periods of virus breakthrough over significant distances downstream from the injection sites. This behavior suggests that simpler models that account for virus adsorption through a retardation factor may yield a misleading assessment of virus transport in &#quot;hydrogeologically sensitive&#quot; subsurface environments.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
| Other project views: | All 14 publications | 4 publications in selected types | All 4 journal articles |
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| Type | Citation | ||
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Bhattacharjee S, Ryan JN, Elimelech M. Virus transport in physically and geochemically heterogeneous subsurface porous media. Journal of Contaminant Hydrology 2002;57(3-4):161-187. |
R826179 (Final) |
not available |
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Ryan JN, Elimelech M, Ard RA, Harvey RW, Johnson PR. Bacteriophage PRD1 and silica colloid transport and recovery in an iron oxide-coated sand aquifer. Environmental Science and Technology 1999;33:63-73. |
R826179 (1998) R826179 (1999) R826179 (Final) |
not available |
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Ryan JN, Metge DW, Harvey RW, Pieper AP, Navigato T, Loveland JP. Is virus inactivation accelerated by attachment to mineral surfaces? Eos, Transactions of the American Geophysical Union 1999;80:F104. |
R826179 (Final) |
not available |
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Ryan JN, Harvey RW, Metge D, Elimelech M, Navigato TN, Pieper AP. Field and laboratory investigations of inactivation of viruses (PRD1 and MS2) attached to iron oxide-coated quartz sand. Environmental Science and Technology 2002;36(11):2403-2413. |
R826179 (Final) |
not available |
Supplemental Keywords:
drinking water, groundwater, risk assessment, virus, environmental chemistry, biology, hydrology., RFA, Scientific Discipline, Air, Water, Waste, Hydrology, Environmental Chemistry, Chemistry, Drinking Water, Groundwater remediation, Engineering, Chemistry, & Physics, monitoring, fate and transport, transport model, microbial risk assessment, pathogenic microbes, aquifer grain, natural disinfection, Groundwater Disinfection Rule, treatment, water quality, virus attachment, inactivation of virusesProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.