USGS - science for a changing world

Environmental Health - Toxic Substances

Investigations - Contaminants of Emerging Concern in the Environment

Onsite Wastewater Systems

Waste samples being collected from an onsite wastewater system for analysis of emerging contaminants
Waste samples being collected from an onsite wastewater system for analysis of emerging contaminants (Photo courtesy of the Colorado School of Mines)

In low population density areas, wastewater management is commonly achieved by onsite wastewater treatment systems. While these systems have been viewed in the past as temporary solutions until centralized treatment facilities became available, they are now an appropriate and necessary component of the wastewater infrastructure of the U.S. Nearly 25 percent of the current U.S. population and a substantial portion of all new development are currently being served by decentralized wastewater systems. While much is known about the characteristics and performance of onsite wastewater systems with respect to conventional pollutants, there is almost no information regarding the occurrence and fate of emerging contaminants in these decentralized systems and the potential for adverse impacts on receiving water to which they discharge.

Thirty onsite wastewater treatment systems were selected from the Colorado Rocky Mountain Region as a representative subset of the types of systems currently in use in the U.S., providing a range of influent sources (residential, commercial, and institutional) and system operation types (conventional septic tank to leach field, or with additional treatment units such as a textile filter or constructed wetlands). The sites were sampled during two distinct hydrologic seasons and analyzed for a suite of emerging contaminants and conventional parameters.

To enhance the understanding of the transport of emerging contaminants in onsite wastewater treatment systems, studies are underway at a field test site at the Colorado School of Mines (CSM) in Golden, Colorado. The Rocky Mountain Onsite and Small Flows Research Program was initiated at CSM to advance the science and engineering of treatment technologies and enhance the long-term viability of decentralized approaches to water infrastructure in Colorado, the U.S., and abroad. This multidisciplinary program involved fundamental and applied research designed to quantify and model key hydraulic and purification processes in decentralized treatment systems. Monitoring and assessment involve sampling and analysis combined with in situ sensors and computer-assisted data acquisition and visualization. Muticomponent tracer and surrogate studies are employed to delineate flow and transport behavior.

Available Publications

DeJong, K.E., Siegrist, R.L., Barber, L.B., and Wren, A.L., 2004, Occurrence of emerging organic chemicals in onsite wastewater system effluents: in Proceedings of the 4nd International conference on pharmaceuticals and endocrine disrupting chemicals in water, Minneapolis, Minn., National Ground Water Association, October 13-15, 2004, CD-ROM, p. 40-41.

Other Related Publications

Hinkle, S.R., Weick, R.J., Johnson, J.M., Cahill, J.D., S.G., S., and Rich, B.J., 2005, Organic wastewater compounds, pharmaceuticals, and coliphage in ground water receiving discharge from onsite wastewater treatment systems near La Pine, Oregon--Occurrence and implications for transport: U.S. Geological Survey Scientific Investigations Report 2005-5055, 98 p.

More Information

  • Project contact: Larry Barber

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