Grantee Research Project Results
2003 Progress Report: Pathogen Transport and Fate During Subsurface Infiltration: Integrated Laboratory and Field Study
EPA Grant Number: R829013Title: Pathogen Transport and Fate During Subsurface Infiltration: Integrated Laboratory and Field Study
Investigators: Brusseau, Mark , Gerba, Charles P. , Blanford, William
Institution: University of Arizona
EPA Project Officer: Page, Angela
Project Period: September 1, 2001 through August 31, 2004 (Extended to August 31, 2005)
Project Period Covered by this Report: September 1, 2002 through August 31, 2003
Project Amount: $519,725
RFA: Drinking Water (2000) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
The overall objective of this research project is to examine the transport and fate of Cryptosporidium parvum oocysts, Giardia muris cysts, and Microsporidium Encephalitozoon intestinales spores during subsurface infiltration (e.g., riverbank filtration, effluent recharge). The specific objectives of this research project are to investigate: (1) the processes influencing transport and fate of the target pathogens in model systems; (2) the transport and fate of target pathogens under the unsaturated conditions present during water infiltration events; and (3) the transport and fate of the target pathogens in a complex field system.
The potential exposure of humans to pathogens in potable water supplies is a significant human health issue. One of the major factors influencing exposure risk is the transport and fate behavior of the pathogens in subsurface systems. A review of the literature shows that limited research has been performed on the subsurface transport and fate behavior of C. parvum oocysts, Giardia muris cysts, and Microsporidium E. intestinales spores. In addition, Cryptosporidium and Microsporidium have been shown to be resistant to chlorination, which is the primary water treatment method in the United States. Thus, although these pathogens are found in the environment, the processes that control their transport and fate from surface waters into groundwater are poorly understood.
Progress Summary:
We have conducted a series of miscible-displacement experiments with Microsporidium intestinales. Preparation for the experiments began with the uniform dry packing of the column with a well-sorted, low organic matter silica sand that has a mean grain size range of 0.59-0.88 mm and an organic matter content of 0.04 percent. The column is saturated with a 0.005 N NaCl electrolyte solution. Pentafluorobenzoic acid is used as a conservative tracer to characterize the hydrodynamic properties of the porous medium. Solutions containing the inactivated M. intestinales then are injected into the column at concentrations of approximately 1.0 E+06 in a solution of 0.005 N NaCl2. The reservoir containing the pathogen solution is agitated throughout the experiment using a stir plate to prevent the settling of the spores. All samples are stored at 4°C prior to slide preparation and analysis. Analysis of the slides is done using an epifluorescence microscope at 1,000X magnification, examining 50 fields of view per slide. The results reveal that a large fraction of the spores pumped through the column are not recovered in the effluent, suggesting removal through processes such as filtration and irreversible sorption. Identifying the specific processes responsible will be a focus of experiments to be conducted in Year 3 of the project. The spores that are recovered in the effluent begin to appear in the effluent at approximately one pore volume, suggesting minimal retention. In general, the transport behavior observed for M. intestinales is similar to that observed for the MS2 coliphage, which was used as a reference control.
We also have begun work on developing a mathematical model to describe pathogen transport and fate in porous media. The model is being designed to incorporate multiple processes specific to pathogen transport. The processes included are reversible sorption, irreversible sorption, surface blockage, accumulation at the air-water interface (for unsaturated conditions), and inactivation.
Future Activities:
We will continue the miscible-displacement experiments for the target pathogens. These experiments will be used to characterize the primary mechanisms influencing the retention and transport of the pathogens. We also will conduct experiments under water-unsaturated conditions. For these, we will characterize the potential impact of accumulation at the air-water interface on pathogen retention and transport. We will complete the development and testing of the mathematical model. The model then will be used to simulate the results obtained from the miscible-displacement experiments.
Journal Articles:
No journal articles submitted with this report: View all 9 publications for this projectSupplemental Keywords:
exposure, exposure and effects, human exposure, health effects, human health, human health effects, human health risk, risk, risk assessment, ecological effects, ecosystem protection, environmental exposure and risk, ecology, bioavailability, drinking water, watersheds, groundwater, land, soil, recharge, filtration, pathogens, infiltration, vadose zone, waste, water, environmental chemistry, fate and transport, groundwater remediation, hydrology, physical processes, Giardia, chlorination, Cryptosporidium, drinking water contaminants, drinking water treatment, Microsporidium, Encephalitozoon, Encephalitozoon intestinales, microbial risk assessment, mobility, modeling, monitoring, pathogens, riverbank filtration, treatment., RFA, Health, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, PHYSICAL ASPECTS, Water, Waste, Ecological Risk Assessment, Health Risk Assessment, Physical Processes, Fate & Transport, Risk Assessments, Environmental Chemistry, Groundwater remediation, Drinking Water, Ecology and Ecosystems, chlorination, encephalitozoon intestinalis, treatment, water quality, infiltration, encephalitozoon, microbial risk assessment, human exposure, monitoring, pathogens, fate and transport, drinking water contaminants, drinking water treatment, exposure, other - risk assessment, Giardia, human health risk, cryptosporidium , human health effects, modeling, microsporidia, mobility, riverbank filtrationProgress 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.