Detecting Fecal Contamination and Its Sources in Water and WatershedsEPA Grant Number: R824782
Title: Detecting Fecal Contamination and Its Sources in Water and Watersheds
Investigators: Sobsey, Mark D.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1995 through October 31, 1998
Project Amount: $400,000
RFA: Water and Watersheds (1995) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Description:Little is known about the levels and sources of fecal contamination in water. There are thus great uncertainties about human and environmental health risks from pathogens. Furthermore, there is inadequate information to reliably prevent and manage human and animal fecal wastes in water and watersheds and the risks of waterborne disease they pose.
The objectives of this project are to develop, evaluate and apply new and improved methods to detect and trace sources of fecal contamination in surface waters. Emphasis is placed on detecting viable or infectious organisms and distinguishing between human and animal sources of fecal contamination.
Initial applications of our methods are being done in the laboratory using spiked (seeded) samples of water and in the field in watersheds that are well characterized with respect to sources of human and animal fecal wastes. One of the indicators we are using, genotypes of male-specific coliphages, have been detected and quantified in watersheds receiving municipal sewage effluent discharges and were found at progressively higher concentrations nearer sites of known sewage effluent discharge. The detected genotypes or serotypes were those expected in human fecal wastes. In watersheds receiving fecal wastes from agricultural animals (cattle, pigs, and poultry), indicators were found at highest concentrations at sample stations impacted by known fecal waste sources. The detected types were those expected in animal fecal wastes, except when the waste source was pigs. Pig wastes sometimes contained indicator types also found in human wastes. Salmonella are being rapidly detected at low levels by several techniques, including: pre-enrichment, membrane filtration, selective growth on differential/selective media and nucleic acid hybridization.
In laboratory investigations of Cryptosporidium oocyst viability assays in cell cultures, as few as 1-10 live oocysts have been detectable by a specialized assay of active stages (meronts). When oocysts are inactivated (for example, by heat treatment), they are not detectable by this assay.
We have made considerable progress in the development and initial field application of new and improved methods to detect indicators of fecal contamination and enteric pathogens in water. Initial field application of these methods shows that levels of indicators are highest nearest sources of fecal contamination. We have a promising approach to distinguish between human and animal sources of fecal contamination in watersheds, but there may be a problem in resolving human from pig fecal waste sources. Cell culture infectivity may prove to be a useful assay to detect low levels of viable Cryptosporidium cysts in water and other environmental samples.
In the future we will further develop, refine and field apply improved methods to detect fecal indicators and enteric pathogens in water. This will be followed by periodic field sampling for enteric bacterial, viral and protozoan pathogens as well as candidate indicator bacteria at a number of well characterized field sites. These field studies will be used to determine the sensitivity, selectivity and specificity of the methods to detect fecal pathogens and their indicators in watersheds and to trace and identify fecal waste sources.