Identifying the Source of Pathogen Contamination of Water

Tracking the source of pathogens has been the focus of considerable scientific effort. The Environmental Pathogens Information Network (EPI-Net) provides information including fact sheets addressing “Tracking Microbial Pathogens” and “Role of Indicators in Pathogen Detection”.

Tracking Methods

Sheridan Haack, PhD, Research Hydrologist/Microbiologist, US Geological Survey, Michigan Water Science Center summarizes tracking methods as follows:

“There are three general ways to determine the sources of microbial contamination of water. The first, and most obvious, is to search the landscape for direct contributions and potential sources and to establish that microorganisms (or the source material) could move from the source area to water. There are several methods, ranging from dye-tracing studies to sophisticated hydrologic modeling, that can establish these connections…

The second method is to examine the affected water for changes in water quality that might arise from the potential source. Nutrients (nitrogen or phosphorous), certain chemicals such as chloride, or the ratios of chemicals such as bromide and chloride, have been used to indicate sources such as septic effluents or manure. More recently, sophisticated analyses have shown that chemicals such as human-use pharmaceuticals or personal care products may be useful in tracking fecal pollution from wastewater treatment plant effluents…

In rural environments, pathogens may originate from confined or pastured livestock, home septic systems, wildlife, or rural community waste treatment systems. Source identification can be challenging. CC2.5 LPELC

Finally, a logical (if not simple or inexpensive) approach is to evaluate whether the fecal indicator bacteria (or pathogens) themselves indicate the source, which is termed “microbial or bacterial source tracking” (MST or BST). In the last 5 years, several reviews of the state of this science have been produced (see references). In general, these reviews indicate that each method can produce some useful results for distinguishing between human, livestock and wildlife sources of fecal pollution, especially for small-scale studies with limited source inputs. However, all these methods have technical difficulties, and most are not ready to be broadly used in support of management decisions. The best approach to source determination is to acquire multiple lines of evidence using several techniques.”

Page Manager. Rick Koelsch, University of Nebraska, and Janice Ward, US Geological Survey.
Reviewed by: Dan Shelton, USDA ARS, Jeanette Thurston-Enriquez, USDA ARS