Assessing riverine sediment-pathogen dynamics: Implications for the management of aquatic and human health risk

While it is established that sediment/floc can harbour a significant quantity of pathogens, the erosion, transport and deposition dynamics of the sediment-associated pathogens is not well understood in relation to ecosystem and human health impact. In this study, annular flume experiments were run with Pseudomonas spp. CTO7::gfj-2 inoculated sediment to assess the erosion, transport and fate of indicator organisms in river systems. Correlative microscopy was used to visually assess the microbial-floc relationship and a flow-cell/shear-cell was used to assess the strength of the indigenous E. coli microbe-floc association. Results indicate that suspended cohesive flocs are the dominant form of pathogen delivery to the sand bed. Significant correlations were found between the indicator organisms (CTO7-gfp and E. coli) suspended solid concentration and shear level. It is concluded that the bed sediment can represent a significant source of pathogenic organisms to the water column, with regulatory water samples not necessarily reflecting recent microbial contamination from terrestrial sources, but also a re-suspension of previously settled pathogens from the river bed. As such, sediment-pathogen dynamics should be considered when identifying source areas, determining aquatic and public health risk, and modelling pathogen transport in river systems. Copyright © 2010 IAHS Press.