Assessing levels of pathogenic contamination in a heavily impacted river used as a drinking-water source

This paper describes initial results from a research program that aims to gain greater understanding of sources of pathogens and the environmental factors that influence their survival and transport in watersheds. An additional goal is to enhance the ability to predict potential levels of pathogenic microorganisms arriving at drinking-water treatment plant intakes. The objectives will be supported by an intensive monitoring program examining the temporal and spatial variability of pathogens in a test watershed (the Grand River Watershed, Ontario). As many as 500,000 people potentially receive at least part of their drinking water from the Grand River. The watershed has significant urban and agricultural use. Sampling for total coliforms, fecal coliforms, Escherichia coli, Escherichia coli O157:H7, and Campylobacter spp. began in July 2002. Although presumptive tests were occasionally positive, no Escherichia coli O157:H7 or Campylobacter spp. were confirmed to be present in water samples taken. Escherichia coli O157:H7 was, however, detected in a tributary of the Grand River during an initial investigation. Preliminary results did not show any statistically significant differences between coliform concentrations upstream and downstream of wastewater treatment plants. Data suggest that nonpoint sources may have a greater effect on routine stream coliform concentrations.