WASTEWATER INDICATOR CHEMICALS IN WASTEWATER EFFLUENT, SURFACE WATERS, AND BED SEDIMENTS IN THE ST. CROIX NATIONAL SCENIC RIVERWAY

Abigail Tomasek, Kathy Lee, and Donald Hansen
USGS Minnesota Water Science Center, Mounds View MN

The U.S. Geological Survey (USGS) and the National Park Service (NPS) collaborated on a project to determine the occurrence of organic wastewater indicator chemicals (OWCs) including compounds used in plastics, surfactant metabolites, antimicrobials, fragrances, fire retardants, and pharmaceuticals associated with wastewater treatment plant (WWTP) effluent in the St. Croix National Scenic Riverway. Treated wastewater effluent from two WWTPs, located in St. Croix Falls, Wisc. (STCFL-WWTP) and Taylors Falls, Minn. (TF-WWTP), was collected from 2007 to 2008. During this time, water and bed sediment samples from the St. Croix River near Sunrise, Minn., upstream from the two WWTPs and from Franconia, Minn., downstream from the WWTPs, also were collected. This area was chosen because of significant mussel populations near these two large WWTP discharge points. The results of this study indicate that aquatic biota in the St. Croix River are exposed to a wide variety of organic contaminants that originate from diverse sources including WWTP effluent. The data collected indicates that exposures are temporally and spatially variable and that OWCs are accumulating in bed sediments. The data also suggests that OWCs in water and bed sediments increase downstream of wastewater discharges to the St. Croix, however, the presence of OWCs in river water and bed sediment at Sunrise indicate that potential sources of these chemicals, either WWTPs or other sources, are upstream from the Taylors Falls-St. Croix Falls area.

A variety of pharmaceuticals and OWCs were detected in effluent from both WWTPs. The chemical constituents detected varied between the two WWTPs and varied over time from samples collected at each site. The concentration and numbers of OWCs detected were greater in the effluent from STCFL-WWTP (39 detected) than from TF-WWTP (20 detected). Four endocrine active chemicals (EACs), chemicals known to affect the endocrine systems of fish, including 4-nonylphenol, 4-nonylphenol diethoxylate, AHTN and HHCB, also were detected at both WWTPs. Concentrations of phosphate flame retardants were greater in effluent from STCFL-WWTP than from TF-WWTP, with the concentration of tris(2-butoxyethyl)phosphate exceeding 200 μg/L. Phosphate flame retardants may be from industrial effluent sources.

Seven OWCs, including one EAC, and two pharmaceuticals were detected in water samples from Sunrise. Twelve OWCs and three pharmaceuticals were detected from Franconia. Eighteen OWCs were detected in bed sediment from Sunrise, while twenty-two were detected in samples from Franconia. Eight pharmaceuticals were detected in bed sediment samples from both sites.

Suggestions for Reading

Lee, K.E., Barber, L.B., Furlong, E.T., Cahill, J.D., Meyer, M.T., and Zaugg, S.D., 2004, Presence and distribution of organic wastewater compounds in wastewater, surface, ground and drinking waters, Minnesota, 2000-02: U.S. Geological Survey Investigation Report 2004-5138, 47 p.

Barber, L.B., Lee, K.E., Swackhamer, D.L., and Schoenfuss, H.L., 2007, Reproductive responses of male fathead minnows exposed to wastewater treatment plant effluent, effluent treated with XAD8 resin, and an environmentally relevant mixture of alkylphenol compounds: Aquatic Toxicology, v. 82, p. 36–46.