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Potential Risk of Suspended Particulate Matter in Aquatic Ecosystems

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  21st Century Watershed Technology: Improving Water Quality and Environment Conference Proceedings, 21-24 February 2010, Universidad EARTH, Costa Rica  701P0210cd.(doi:10.13031/2013.29448)
Authors:   Sandra M Tirado, Ian G Droppo, Steven N Liss
Keywords:   Keywords: microbial floc, water quality, indicator organisms, pathogens, extracellular polymeric substances (EPS), correlative microscopy

Monitoring methods for health risk assessment in water rely on the presence or absence of indicator organisms within the reservoir, and primarily the suspended organisms in the water column. This is not an adequate indication of environmental conditions due to the associations of pathogens with sediment compartments (suspended and bed). In this study four different aquatic environments were sampled to assess the physico-chemical properties of floc-microorganism association. A combination of microbiological and various physico-chemical properties were examined in sediment and water samples employing a combination of field and laboratory techniques. These included estimations for total coliforms as indication of pathogens, microscopy analysis and particle size determination at different energy impacts (simulated flow conditions (SFC). A baffled jar test was used to assess the strength of the floc- microorganism association by applying increasing agitation speeds (SFC) to the floc. Results showed a significant increase (p = 0.05) in the total coliform counts with agitation speeds higher than 400rpm, corroborating the detachment of bacteria. Overall increases in agitation speed significantly changes the particle size distribution. Larger particles were observed in those sites where the organic content of the flocs and sediments were higher. Correlative microscopic analysis suggests a large presence of extracellular polymeric substances (EPS) in floc samples which contribute to retention on the floc, thus leading to microbial protection. Results show that the bioorganic component in flocs and the energy impacts in aquatic systems play a key role for the assessment of pathogen risk in water systems.

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