Page Banner

United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
Detection, quantification, and characterization of pathogen behavior in different environmental matrices; determine inactivation/survival rates and transport characteristics of fecal coliform and pathogens from manure sources to surface or ground water; determine sources of nonpoint fecal pollution at the Santa Ana River Watershed by bacterial source tracking technology; quantify important mechanisms influencing the transport and retention of pathogenic microorganisms in subsurface environments; adapt and improve numerical models for simulating the environmental transport and fate of pathogenic microorganisms; and develop and optimize manure and lagoon water treatment strategies to minimize the transmission of pathogenic microorganisms to food and water resources.

1b.Approach (from AD-416)
Conduct laboratory, lysimeter and field experiments to examine the important physical, chemical, and biological processes affecting the fate and transport of pathogenic microorganisms in manure-soil-water systems. Laboratory studies will determine the important processes and mechanisms affecting pathogen survival. Studies will be conducted at various scales using culture and molecular approaches to investigate pathogen movement in surface water and soil. Measurements of pathogen concentration, soil and environmental conditions will be collected to allow the simulation of pathogen transport. As new information becomes available, existing models will be improved to enhance the prediction of pathogen transport to surface water, ground water, and the environment. Coupling laboratory and field scale experiments with simulation studies, new strategies will be developed to control the movement of pathogenic microorganisms from animal feeding operations to human food and the environment. Research will be conducted in collaboration with the Food Safety Research, WRRC, Albany, CA. 5310-42000-002-00D (5/01).

3.Progress Report
Evaluation of a rapid method for quantifying assimilable organic carbon (AOC) in surface water. This study was designed to evaluate new methods for rapid determination of assimilable organic carbon (AOC) in drinking water, surface water and sediment by researchers at Orange County Water District and the United States Salinity lab. The AOC represents a fraction of the total organic carbon (TOC) in water that bacteria can use for regrowth and other metabolic processes thus affecting fate and transport of pathogenic bacteria. High levels of AOC are associated with rapid biofilm formation, loss of membrane performance and poor water quality. A rapid bioassay made available by Checklight was evaluated for its speed, sensitivity, accuracy and complexity to perform the assay. A number of defined tests were run using the Checklight bioassay and it was determined that the sensitivity ranged from 3-100ppb using a mixed carbon solution. Whereas, the sensitivity range using simple and complex carbon compounds ranged from 5-100ppb. Light produced by Vibrio fischeri cells used in the assay was greater with glucose and fructose-carbon than with glycerol, sodium acetate and the mixed carbon solution. The Coulter Multizer was used to observe an increase in cell biomass by measuring cell volume. The Checklight assay was evaluated under defined and controlled conditions and it was determined that the assay is highly variable due to the physiology of Vibrio fischeri cells. Several modifications were made in the study that improved the variability, sensitivity and accuracy of the assay. It was concluded that cells should be grown in mass using a chemostat, which would result in cells that are physiologically stable and in the same growth phase when they are harvested for the bioassay.

1. Pathogen transport and retention in porous media. An improved understanding of the transport and fate of pathogenic microorganisms is needed to protect food and water resources from the pathogen contamination. ARS researchers at Riverside, CA, in cooperation with faculty and students at the University of California, Riverside and Lawerence Berkeley National Laboratory, have conducted experimental and theoretical work to study the transport and retention of pathogens (Cryptospordium parvum, Salmonella pullorum, and Escherichia coli O157:H7). Pathogens were found to be weakly associated with the solid phase under conditions that are typical for most natural enviroments, and water flow may funnel microbes to regions where they may be retained. The extent to which microbe rentention will occur in these locations is a function of the system chemistry, the pore space geometry and the microbe concentration. One consequence of enhanced pathogen retention in low velocity regions is that only a small fraction of the surface area may contribute to retention and that these regions may fill over time, thereby enhancing pathogen transport. This research will aid in the development of improved mathematical models to predict the fate of pathogens in the environment, and management practices to minimize the risk of contamination.

2. Variations of Indicator bacteria in a large urban watershed. In currently available data from the Santa Ana River, Southern California, USA watersheds demonstrate that both existing and Environmental Protection Agency (EPA)-recommended bacteria water quality criteria are routinely exceeded in the watersheds, often by one or more orders of magnitude. Total coliform (TC), fecal coliform (FC), E. coli, enterococci, and total bacterial concentrations were monitored by ARS scientists at Riverside, CA in 13 locations in the watershed over a two year period. The water flow effects indicated that the recessional water flow transported significantly lower bacterial counts into the watershed than either the dry weather flow or the storm or wet weather flow. Also, bacterial count estimates changed far more significantly across different sites, in comparison to estimates across seasonal flow estimates or time. These results imply that TC, FC, E. coli, and enterococci bacterial counts in the two tributaries were strongly influenced by spatial location effects with contamination due to local agricultural and/or urban run-off, as opposed to elevated up-stream contamination and/or discharge contamination associated with the two Wastewater Treatment Plants(WWPT). Therefore, this study has provided useful information that could be used in constructing watershed management plans for a mixed watershed.

Review Publications
Tazehkand, S.S., Torkzaban, S., Bradford, S.A., Walker, S. 2008. Cell preparation methods influence E.coli D21g surface chemistry and transport in saturated sand. Journal of Environmental Quality. 37:2108-2115.

Bradford, S.A., Torkzaban, S., Leij, F., Simunek, J., Van Genuchten, M.T. 2009. Modeling the Coupled Effects of Pore Space Geometry and Velocity on Colloid Transport and Retention. Water Resources Research. 45:1-15.

Haznedaroglu, B.Z., Kim, H.N., Bradford, S.A., Walker, S.L. 2009. Relative Transport Behavior of Escherichia coli O157:H7 and Salmonella enterica serovar Pullorum in Packed Bed Column Systems: Influence of Solution Chemistry and Cell Concentration. Environmental Science and Technology. 43(6):1838-1844.

Segal, E., Bradford, S.A., Shouse, P.J., Lazarovitch, N., Corwin, D.L. 2008. Integration of Hard and Soft Data to Characterize Field-Scale Hydraulic Properties for Flow and Transport Studies. Vadose Zone Journal. 7(3):878-889.

Bradford, S.A., Segal, E. 2009. Fate of Indicator Microorganisms Under Nutrient Management Plan Conditions. Journal of Environmental Quality. 38:1728-1738.

Bradford, S.A., Segal, E., Zhang, W., Wang, Q. 2008. Reuse of concentrated animal feed operation wastewater on agricultural lands. Journal of Environmental Quality. 37:S97-S115.

Corwin, D.L., Bradford, S.A. 2008. Environmental Impacts and Sustainability of Degraded Water Reuse. Journal of Environmental Quality. 37:S1-S7.

Kim, H., Bradford, S.A., Walker, S. 2009. Escherichia coli O157:H7 Transport in Saturated Porous Media: Role of Solution Chemistry and Surface Macromolecules. Journal of Environmental Science & Technology, 43(12):4340-4347.

Last Modified: 4/19/2014
Footer Content Back to Top of Page