Grantee Research Project Results
2002 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, 2001 through August 31, 2002
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., river- bank 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, G. 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:
The initial work for this research project is based on the use of miscible-displacement experimentation. A column is packed with a well-characterized porous medium, and solutions containing the solute of interest (nonreactive tracer, pathogen) are pumped into the column. Effluent from the column is sampled and analyzed to obtain solute concentrations. These initial experiments are conducted under water-saturated conditions.
We have conducted a series of experiments with MS2 coliphage, a widely used model virus, to establish a "control" data set to which the pathogen transport data can be compared. The results of these experiments show that a large fraction of the injected virus, approximately 45 percent, traveled through the soil at the same velocity as water. In other words, minimal retention was observed for a large fraction of the viruses. The remaining virus appeared to have been retained within the soil through quasi-irreversible sorption mechanisms, and also may have been influenced by inactivation.
Difficulties were encountered in the initial target pathogen miscible-displacement experiments, for which Microsporidium intestinales is being used. An extended period of troubleshooting was required to resolve these issues. One major problem was that the M. intestinales supply was degrading over time. Through discussion with the supplier, we found that the problem was a result of their method of preparing the organism stock supply. Specifically, the formalin used to kill and preserve the micro-organisms was breaking down the spore structure. As a result, we have changed our supplier. We now are receiving live organisms from a provider at the University of Arizona that we then inactivate using ultraviolet light before use.
Problems also were encountered in the preparation and analyses of the slides used for spore quantification. One problem stemmed from the presence of particulate matter in the solution that appeared to be adsorbing the dye. This was addressed by filtering all solutions through a 0.22 µm cellulose acetate filter to remove particulate matter. Another problem in the enumeration of the C. parvum and M. intestinales is related to the tendency of the spores to clump. To remedy this, a surfactant such as Tween 80 is being added to the sample before filtering to reduce clumping. In addition, the initial experiments were conducted using 0.01 N CaCl2 as the background electrolyte. We have found that this enhances clumping of the spores; thus, future experiments will be conducted using 0.005 N NaCl.
Future Activities:
We will continue the miscible-displacement experiments for the target pathogens. As noted above, we will use NaCl as the background electrolyte to help minimize clumping problems. These experiments will be used to characterize the primary mechanisms influencing the retention and transport of the pathogens.
Journal Articles:
No journal articles submitted with this report: View all 9 publications for this projectSupplemental Keywords:
exposure, risk, risk assessment, health effects, human health effects, human health risk, microbial risk assessment, ecological effects, human health, environmental exposure and risk, health, bioavailability, drinking water, watersheds, groundwater, land, soil, recharge, filtration, pathogens, infiltration, vadose zone, ecosystem protection, waste, water, ecology and ecosystems, environmental chemistry, fate and transport, groundwater remediation, hydrology, physical processes, chlorination, Cryptosporidium, Microsporidium, Giardia, Encephalitozoon, Encephalitozoon intestinales, drinking water contaminants, drinking water treatment, exposure and effects, human exposure, 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.