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(46-03) Modeling Transport and Decay of Pathogens and Toxicants in Surface Water. Frick, Walter*,1, Denton, Debra2, Khangaonkar, Tarang3, Molina, Marirosa1, Roberts, Philip4, Santodomingo, Jorge5, 1 U.S. EPA, Ecosystems Research Division, Athens, GA, USA2 U.S. EPA, Region 9, San Francisco, CA, USA3 Foster Wheeler Environmental Corporation, Bothell, WA, USA4 Department of Civil Engineering, Atlanta, GA, USA5 U.S. EPA, NRMRL, Cincinnati, OH, USA ABSTRACT- The presence of pathogens and toxicants in surface waters poses risks to human health and ecological systems. Both point and non-point sources contribute to the abundance of these pollutants. In physical transport terms, both mixing zone plume models and hydrodynamic models have attained a reasonably high degree of accuracy. However, the integration of the two types of models lags behind specialized model development. Principal problems inhibiting integration include the widely different length and time scales governing initial dilution and far-field transport processes. Integration becomes more problematic when trying to include mechanisms to account for the growth and decay of pathogenic bacteria and other water-borne pathogens. Pathogen survival is a function of a multitude of stressors, which include physical, chemical and biological factors such as nutrient limitation, redox potential, toxic chemicals, viral infection, zooplankton predation, etc. This modeling effort represents an initial attempt to integrate three types of models: (i) an initial dilution model, based on the EPA Visual Plumes; (ii) simple and hydrodynamic transport algorithms and models; and (iii) pathogen and toxicant bacterial response models. The results are compared to limited data available from surf-zone measurement programs. A sensitivity analysis puts the predictions into a statistical framework. Key words: dilution, transport, pathogen, bacteria |
