The Impact of Human Activity on E. coli and Total Coliform Levels in Surface Water
Faculty Mentor Information
Walter Mueller, Accurate Testing Labs
Presentation Date
7-16-2026
Abstract
Northern Idaho is well known for its beautiful lakes, which frequently draw locals and tourists alike to their shores to enjoy recreational activities. As more people seek relief from warming temperatures in local lakes and rivers, the risk of exposure to contaminated water rises. Coliforms, such as Escherichia coli (), are bacteria that naturally occur in the intestines of warm-blooded animals and serve as indicator organisms for fecal contamination and the potential presence of harmful pathogens. Research exists on the effects of these bacteria on human health, but little data exists on the exact connections between recreational activity and coliform levels. This study examined the differences in coliform levels between natural and recreation areas in five Northern Idaho lakes with varying conditions. The samples were analyzed using the EPA standard method 9223B, an Enzyme Substrate Test for the IDEXX Quanti-Tray system, and Colilert substrate. Results showed that non-recreational sites consistently had higher total coliform and E. coli counts. This suggests that human activity may be related to lower coliform levels and that public beaches remain relatively free of health hazards despite the increase in potential sources of contamination.
The Impact of Human Activity on E. coli and Total Coliform Levels in Surface Water
Northern Idaho is well known for its beautiful lakes, which frequently draw locals and tourists alike to their shores to enjoy recreational activities. As more people seek relief from warming temperatures in local lakes and rivers, the risk of exposure to contaminated water rises. Coliforms, such as Escherichia coli (), are bacteria that naturally occur in the intestines of warm-blooded animals and serve as indicator organisms for fecal contamination and the potential presence of harmful pathogens. Research exists on the effects of these bacteria on human health, but little data exists on the exact connections between recreational activity and coliform levels. This study examined the differences in coliform levels between natural and recreation areas in five Northern Idaho lakes with varying conditions. The samples were analyzed using the EPA standard method 9223B, an Enzyme Substrate Test for the IDEXX Quanti-Tray system, and Colilert substrate. Results showed that non-recreational sites consistently had higher total coliform and E. coli counts. This suggests that human activity may be related to lower coliform levels and that public beaches remain relatively free of health hazards despite the increase in potential sources of contamination.