HR: 1340h
AN: H33F-1701    [Abstracts]
TI: Processes affecting the transport of Cryptosporidium parvum and other persistent pathogens in surface- and ground-waters
AU: * Packman, A I
EM: a-packman@northwestern.edu
AF: Northwestern University, Dept. of Civil and Environmental Engineering 2145 Sheridan Rd., Evanston, IL 60208, United States
AU: Lau, B L
EM: boris-lau@northwestern.edu
AF: Northwestern University, Dept. of Civil and Environmental Engineering 2145 Sheridan Rd., Evanston, IL 60208, United States
AU: Harter, T
EM: thharter@ucdavis.edu
AF: University of California-Davis, Department of Land, Air and Water Resources and Kearney Agricultural Center, Veihmeyer Hall, University of California, Davis, CA 95616-8628, United States
AU: Atwill, E R
EM: ratwill@ucdavis.edu
AF: University of California-Davis, School of Veterinary Medicine Room 1383, Surge III University of California-Davis One Shields Ave, Davis, CA 95616-8734, United States
AB: Waterborne diseases are transmitted through numerous environmental pathways, and their migration is strongly mediated by interaction with a wide variety of sediments and other natural materials during transport. Here we provide an overview of factors that affect the fate of persistent water-borne pathogens, focusing particularly on the zoonotic pathogen Cryptosporidium parvum as an example. While individual microbial cells are both small and have low specific gravity, suggesting that they should be highly mobile and remain suspended for long periods of time, attachment to a variety of background materials can substantially reduce pathogen mobility. Cryptosporidium oocysts readily associate with both inorganic and organic particles, resulting in the formation of aggregates. This process tends to increase the effective settling velocity of C. parvum in surface waters. Similarly, pathogens readily become associated with the solid matrix during transport in groundwater, resulting in removal by filtration. However, this process is reversible with C. parvum, resulting in a slow long-term release following the initial deposition. Pathogens also become associated with biofilms, which are surface-attached communities of microorganisms in a gelatinous matrix. The presence of biofilms increases the immobilization and retention of Cryptosporidium on solid surfaces. All of these processes influence pathogen transmission in surface waters such as rivers and water-supply canals. In these environments, pathogens can be immobilized by deposition into stable sediment beds by a combination of gravitational sedimentation and advection into pore waters followed by subsurface filtration. Association with background suspended matter tends to increase pathogen deposition by sedimentation, and the presence of benthic (sedimentary) biofilms also tends to increase pathogen retention. For pathogens that remain viable for long periods of time in natural aquatic systems, as is the case with Cryptosporidium and other cyst-and spore-forming organisms, then the sediments and sedimentary biofilms become an environmental reservoir of pathogens. Cysts retained in biofilms appear to be relatively difficult to resuspend, but slow, long-term biological release and high-flow events that mobilize streambed sediments both deliver pathogens into transport.
DE: 0402 Agricultural systems
DE: 0408 Benthic processes (4804)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 1813 Eco-hydrology
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Fall Meeting