Deposition of Cryptosporidium Oocysts in Streambeds

Abstract

The transfer of Cryptosporidium oocysts from the surface water to the sediment beds of streams and rivers influences their migration in surface waters. We used controlled laboratory flume experiments to investigate the deposition of suspended Cryptosporidium parvum oocysts in streambeds. The experimental results demonstrate that hydrodynamic interactions between an overlying flow and a sediment bed cause oocysts to accumulate in the sediments and reduce their concentrations in the surface water. The association of C. parvum with other suspended sediments increased both the oocysts' effective settling velocity and the rate at which oocysts were transferred to the sediment bed. A model for the stream-subsurface exchange of colloidal particles, including physical transport and physicochemical interactions with sediment grains, accurately represented the deposition of both free C. parvum oocysts and oocysts that were attached to suspended sediments. We believe that these pathogen-sediment interactions play an important role in regulating the concentrations of Cryptosporidium in streams and rivers and should be taken into consideration when predicting the fate of pathogens in the environment.

Risk of Gastrointestinal Disease Associated with Exposure to Pathogens in the Sediments of the Lower Passaic River

“…High concentrations of microorganisms that are typically associated with sewage were observed in this analysis, but it is difficult to definitively relate sediment concentrations to CSO discharge events without additional data. Previous studies have demonstrated that CSOs can and do impact the pathogen load in the sediment near the outfall (15,16,46,48,49,80). One important difference between these studies and this analysis is that prior studies usually addressed a single CSO.…”

“…While the exposure scenarios included in this assessment were focused primarily upon direct and/or indirect ingestion of water during a variety of activities (e.g., boating, picnicking, fishing, and swimming), many of these activities would also involve direct contact with sediments as well as the water. As sediments may act as a reservoir for pathogens (16,18,40,45,46,48,80), it is important that they, too, be evaluated to determine if they pose a potential risk to human health.…”

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

“…A 3-log reduction in the infectivity of PV1 was observed in 14 days in seawater having marine sediments, whereas such a reduction was observed in 4 days in seawater without sediments (23). These results suggest that environmental sediments have a protective effect on pathogens (1,20), and the association of pathogens with environmental sediments cannot be ignored when considering the fate of pathogens in water environments (22).…”

“…Bacterial (Mycobacterium avium [29] and Clostridium botulinum type E [19]), protozoan (Cryptosporidium species [22]), and viral (enterovirus [EV] [5,13,15], hepatitis A virus [HAV] [6,14], and rotavirus [6]) pathogens have been detected in environmental sediments. Whittington et al reported previously that M. avium in sediments from a dam lake survived 12 to 26 weeks longer than it did in a water column (29).…”

Imaging of colloidal deposits in granular porous media by X‐ray difference micro‐tomography

“…[2] The deposition of colloidal particles in a porous medium is relevant in a broad range of environmental and geophysical problems, such as oil extraction [Moghadasi et al, 2004], subsurface contaminant transport [Kretzschmar et al, 1999], siltation of streambeds [Packman et al, 2000], transmission of pathogens in surface and subsurface waters [Searcy et al, 2006], and water treatment involving filtration in both granular beds and membranes [Elimelech et al, 1995]. Filtration models, summarized by [McDowell-Boyer et al, 1986;Elimelech et al, 1995;Tufenkji and Elimelech, 2004], normally assume fixed pore geometry and parameterize deposition rates in terms of the size ratio between mobile suspended particles and pore spaces.…”