Hydrologic Modeling of Pathogen Fate and Transport

Abstract

A watershed-scale fate and transport model has been developed for Escherichia coli and several waterborne pathogens: Cryptosporidiumspp., Giardiaspp., Campylobacter spp, and E. coli O157:H7. The objectives were to determine the primary sources of pathogenic contamination in a watershed used for drinking water supply and to gain a greater understanding of the factors that most influence their survival and transport. To predict the levels of indicator bacteria and pathogens in surface water, an existing hydrologic model, WATFLOOD, was augmented for pathogen transport and tested on a watershed in Southwestern Ontario, Canada. The pathogen model considered transport as a result of overland flow, subsurface flow to tile drainage systems, and in-stream routing. The model predicted that most microorganisms entering the stream from land-based sources enter the stream from tile drainage systems rather than overland transport. Although the model predicted overland transport to be rare, when it occurred, it corresponded to the highest observed and modeled microbial concentrations. Furthermore, rapid increases in measured E. coli concentrations during storm events suggested that the resuspension of microorganisms from stream sediments may be of equal or greater importance than land-based sources of pathogens.

Comparison of the presence and partitioning behavior of indicator organisms and Salmonella spp. in an urban watershed

“…Despite the relatively large impact of nonpoint source pollution on instream microbial concentrations, quantitative data describing microbial transport in surface water is sparse and limits the reliability of modeling efforts ( Jamieson et al 2004a;Dorner et al 2006;Pachepsky et al 2006;Arnone & Walling 2007;Benham et al 2008;Keller & Cavallaro 2008). Specifically, microbes are generally modeled as individual free cells of near-neutral buoyancy, doi: 10.2166/wh.2009.232 even though increasing evidence suggests that many microorganisms partition between a particle-associated and free (unassociated) phase (Ferguson et al 2003).…”

Development of an Effective Method for Recovery of Viral Genomic RNA from Environmental Silty Sediments for Quantitative Molecular Detection

“…Dorner et al indicated previously the importance of the resuspension of microorganisms from stream sediments rather than land-based sources according to the hydrological simulation of Escherichia coli during storm events (4). The quantitative detection of pathogens in environmental sediments is thus crucial for assessing the health effects of exposure to pathogen-contaminated sediments or pathogen-resuspended water.…”

Transport of E. coli D21g with runoff water under different solution chemistry conditions and surface slopes

“…High concentrations of pathogens, indicator microorganisms, and other colloids can be rapidly transported from agricultural fields, urban environments, and hillslopes to streams or locations of surface water storage by runoff water (Rahe et al, 1978;Heathwaite et al, 2005;Haygarth et al, 2006). Runoff has been reported to be the primary transport route for pathogen dissemination at the hillslope scale (Tyrrel and Quinton, 2003;Jamieson et al, 2004;Dorner et al, 2006). An understanding of processes that influence the transport of pathogens and indicator microorganisms in runoff water is therefore needed to assess and mitigate risks of microbial contamination of surface water supplies to human health.…”