Skip Links

USGS - science for a changing world

Fact Sheet 2015–3023

Contaminant Removal by Wastewater Treatment Plants in the Stillaguamish River Basin, Washington

By Jack E. Barbash, Patrick W. Moran, Richard J. Wagner, and Mike Wolanek

Thumbnail of and link to report PDF (1.1 MB)Introduction

Human activities in most areas of the developed world typically release nutrients, pharmaceuticals, personal care products, pesticides, and other contaminants into the environment, many of which reach freshwater ecosystems. In urbanized areas, wastewater treatment plants (WWTPs) are critical facilities for collecting and reducing the amounts of wastewater contaminants (WWCs) that ultimately discharge to rivers, coastal areas, and groundwater. Most WWTPs use multiple methods to remove contaminants from wastewater. These include physical methods to remove solid materials (primary treatment), biological and chemical methods to remove most organic matter (secondary treatment), advanced methods to reduce the concentrations of various contaminants such as nitrogen, phosphorus and (or) synthetic organic compounds (tertiary treatment), and disinfection prior to discharge (Metcalf and Eddy, Inc., 1979). This study examined the extent to which 114 organic WWCs were removed by each of three WWTPs, prior to discharge to freshwater and marine ecosystems, in a rapidly developing area in northwestern Washington State. Removal percentages for each WWC were estimated by comparing the concentrations measured in the WWTP influents with those measured in the effluents. The investigation was carried out in the 700-mi2 Stillaguamish River Basin, the fifth largest watershed that discharges to Puget Sound (fig. 1).

First posted March 19, 2015

For additional information, contact:
Director, Washington Water Science Center
U.S. Geological Survey
934 Broadway, Suite 300
Tacoma, Washington 98402

Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge. More information about viewing, downloading, and printing report files can be found here.

Suggested citation:

Barbash, J.E., Moran, P.W., Wagner, R.J., and Wolanek, M., 2015, Contaminant removal by wastewater treatment plants in the Stillaguamish River Basin, Washington: U.S. Geological Survey Fact Sheet 2015–3023, 4 p.,

ISSN 2327-6932 (online)



Study Sites and Methods

Contaminant Removal by the Wastewater Treatment Plants


References Cited

Accessibility FOIA Privacy Policies and Notices logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Contact USGS
Page Last Modified: Tuesday, November 29, 2016, 06:34:33 PM