WATERSHED TESTING FOR SOURCE-SPECIFIC INDICATOR ORGANISMS

The use of indicator organisms by water utilities and environmental regulators to assure the microbial safety of drinking water is a widely applied and accepted practice. With improvements in epidemiological methods and medical diagnostics, it has become apparent that traditional coliform indicators are not always appropriate indicators of all human pathogens, especially some recently recognized non-bacterial pathogens. Drinking water contaminated with human waste typically is associated with high risk of infection by human pathogens. Thus, source-specific indicators to identify the contamination source(s) would be very useful. New or alternative source-specific indicators must be established to be highly associated with the human or animal group for which they are specific. These indicators must also be analyzed using methods easily applicable to utility laboratories and boards of sanitation. This research was oriented to determine the potential use of three alternative source-specific indicator organisms (sorbitol-fermenting Bifidobacteria, Rhodococcus coprophilus, and serogroups of F+coliphages) to differentiate human vs. grazing animal, and human vs. non-human microbial inputs in a drinking water watershed. Samples were collected monthly over 13 months from three locations within a drinking water watershed. The incidence of detecting the three alternative indicators corresponded to elevated levels of coliforms and predicted impacts from land use information. The data in this study indicated that the three proposed indicators might be good tools that could be used to discriminate between sources of microbial inputs to drinking water sources.