2011 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.
This is the final report for the project 5310-32000-002-00D entitled “Detection, Source Identification, Environmental Transport, Fate, and Treatment of Pathogenic Microorganisms Derived From Animal Wastes”. This project was terminated on April 2, 2010 and replaced with project 5310-32000-003-00D. Substantial results were realized over the 5 years of this project. This information is summarized below.
The prevalence, diversity, and antimicrobial activities of E. coli from different sources within the Santa Ana River watershed were studied. E. coli from human sources were found to be more diverse and to carry more multiple resistances to different antibiotics than animal sources. The prevalence of pathogens associated with different sources of fecal pollution suggest that Enterococcus and generic E. coli may be useful as indicators of fecal contamination, but they may not be suitable to directly predict public health risks. The microbial diversity and survival of E. coli O157:H7 was studied during preplant fumigation. Lower microbial diversity enhanced the survival of E. coli O157:H7 in some soils following fumigation. A free surface constructed wetland was optimized for the improvement of ground and surface water quality within the Santa Ana River watershed.
Significant field, experimental, theoretical, and mathematical modeling studies have examined the transport, retention, and release of pathogens in soils and aquifers. In summary, we have: (1) identified the importance of grain-grain contacts and eddy zones on microbe retention in porous media; (2) quantified the coupled influence of hydrodynamics, solution chemistry, and pore-structure on microbe retention in both saturated and unsaturated porous media; (3) refined theory to quantify and simulate the applied (hydrodynamic) and resisting (adhesive) torques that act on microbes near solid surfaces and determine rolling or immobilization of microbes on the solid phase; (4) improved our understanding of the roles of surface macromolecules (polymer bridging and electrosteric repulsion) on microbe transport, retention, and aggregation; (5) recognized the importance and developed theory to describe the influence of microbe concentration on retention processes; (6) quantified microbe release with transients in solution chemistry; and (7) developed and utilized simulation techniques and tools to quantify microbe transport, retention, and release at various transport scales. This research has had a significant impact on the surface and subsurface microbe transport community in that they provide a viable framework to describe microbe retention in porous media under unfavorable attachment conditions.