AWWA ACE65124

AWWA ACE65124 Seasonal Distribution of Pathogens and Indicator Organisms in Biofilms in an Agricultural Watershed
Conference Proceeding by American Water Works Association, 06/01/2007

Maal-Bared, Rasha; Bartlett, Karen H.; Bowie, William R.; Hall, Eric R.; Hall, Ken J.

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Monitoring water quality is an essential component of the delivery of safe drinking water.However, current microbial evaluation techniques are neither time-efficient nor cost-effective.Standard techniques monitor for innocuous indicator bacteria, which often do not correlate withpathogen concentrations, and bacterial attachment and survival in biofilms are rarely examined.The presence of pathogens protected in the biofilm matrix is compounded in rural agriculturalareas, where both faecal contamination of water sources and the potential of exposure are veryhigh. This research attempts to improve the understanding of pathogen behavior inagricultural watersheds and evaluate substrate surfaces that could be used for standard protocolsto monitor for the presence of pathogens that cause disease and economic losses in rural Canadianwater systems and around the world. To do so, the authors monitored the presence of faecalcontamination indicators (Heterotrophic plate counts, faecal coliforms, enterococci, and E. coli)and particular pathogens (Pathogenic E. coli 0157 and Salmonella sp.) in water, sediment, and inbiofilms on river and slate rock, wood, sandpaper, and Lexan in Elk Creek (Fraser Valley,British Columbia, Canada) from December 2005 to December 2006. Faecal indicatorconcentrations and pathogen presence were evaluated using standard culturing and isolationmethods. Results showed that monitoring for bacterial indicator concentrations in water columngrab samples greatly underestimated the number of indicator bacteria and pathogens present ateach site. The results also showed that water column grab samples, especially during the dryseason, were not representative of pathogens present in the watershed. This indicates that biofilmsmight be the main reservoir of Salmonella sp. and pathogenic E. coli O157 during the summertime when rainfall and manure application is low. Includes 38 references, tables, figures.