Using eDNA to test for pathogens in reused water
Determining the safety of reused water is important as the use of reused water is only going to increase as
drought conditions continue in the western United States. Reused water can be used for many different purposes,
including agriculture, cooling towers, boilers, and human consumption. With the recycling of water there is a
possibility that pathogens (protozoa, bacteria, and viruses) will be able to survive water treatment, and pose a
hazard to human and agricultural health. The technology and methods for detecting these pathogens in water has
expanded over the last ten years. One area of interest is the detection of the DNA that these organisms leave in
the water. Environmental DNA (eDNA) can be extracellular (free floating DNA) or intercellular (still within the cell).
At this time it is not possible to differentiate between these two sources of DNA, making it impossible to
determine if the organism of interest is alive or dead. To overcome this issue, researchers are working on new
PCR methods that will allow them to determine the viability of an organism. This project has three goals. The first
step will be to research and determine if there are ways to enhance current PCR methods and allow for the
determination of viability of the organism. Second, non pathogenic organisms will be used to determine how well
different water reuse treatments are able to remove these organisms from water. Finally, water samples will be
collected to from multiple places within a water reuse facility and tested for the presence of pathogens to
determine where the issues are in treatment.
Need and Benefit
As the human population continues to grow in the west and drought conditions continue, reusing water for
human consumption (direct potable use) will become an issue that must be addressed. The safety of this water for
human use must be assessed. Reused water has an increased likelihood of containing pathogens and it is
important to be able to analyze water samples to test for the presence of the pathogens and viability. The project
proposed here will is a starting place for determining what molecular testing methods are currently available to
test for viability of the pathogens in water. If these tests exist, the next step will be to test these methods with
controlled samples containing known concentrations of the inactivated pathogen of interest. If the methods are
effective, samples from water treatment facilities will be tested and the results will be compared to traditional
testing methods. This work is important to Reclamation because we are the nation's largest wholesale supplier of
water. The risk of pathogens in water transport that may cause human or animal illness are of concern for
Reclamation. Finally, knowing how to determine the viability of pathogens in water samples is a technology that
can be useful to several applications. One of the biggest issues with eDNA analysis is that it is impossible to
determine if an organism was alive or dead when the sample is collected. This is important information, because
if a pathogen was dead when collected that means that the threat to human health goes down. However, if a
pathogen were alive, there is a chance that it could cause human illness. This proposal is a starting place in
finding and developing the necessary methods to determine the viability of a pathogen in a water sample. The
field of eDNA research is advancing and Reclamation needs to invest in learning this technology so that it can be
applied to projects that are ongoing at Reclamation.
Contact the Principal Investigator for information about partners.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Using eDNA to test for pathogens in reused water (final, PDF,
By Jacque Keele
Publication completed on September 30, 2016