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Evaluating impacts of pulp and paper mill process changes on bioactive contaminant loading to the St. Louis River, Duluth, MN
Citation:
Kahl, M., G. Ankley, J. Cavallin, E. Eid, M. Hughes, K. Jensen, J. Mayasich, E. Randolph, K. Stevens, AND Dan Villeneuve. Evaluating impacts of pulp and paper mill process changes on bioactive contaminant loading to the St. Louis River, Duluth, MN. SETAC North America, Salt Lake City, UT, November 01 - 05, 2015.
Impact/Purpose:
not applicable
Description:
Past in vivo and in vitro studies have found estrogenic and aryl hydrocarbon receptor (AhR)-mediated bioactivities associated with final treated effluent from a wastewater treatment plant (WWTP) discharging to the St. Louis River Area of Concern near Duluth, MN, USA. A long-standing question has been the relative contribution of domestic (accounting for around 55% of inflow) versus industrial sources, including a local pulp and paper mill (PPM) effluent (PPE), which accounts for around 45% of inflow, to these bioactivities. During the summer of 2013 the PPM underwent a series of process changes which could potentially influence the contaminant loading into the WWTP. A series of effects-based monitoring studies on final treated effluent and receiving water were conducted pre-, during, and post-PPM process changes to determine whether they markedly affected bioactivity associated with the final treated effluent. Fathead minnows were exposed to a constant flow of effluent of varying concentrations (100%, 50%, 5%) on-site at the WWTP or caged within the St. Louis River receiving water. Estrogenic activity, as determined using an in vitro bioassay, was not markedly altered by the PPM process changes. Hepatic vitellogenin (vtg) mRNA abundance was consistently elevated in males exposed to 100% effluent, but not in those exposed to 20%, 5% or in the receiving water. Cytochrome P4501a1 (cyp1a1) mRNA expression in male liver was also induced in a concentration-dependent manner. While the magnitude of fold-change in the expression of vtg and cyp1a1 mRNA varied over the time-course of PPM process changes, the variation observed could not be definitively linked to changes in effluent composition, as reflected by the concentrations of approximately 70 organic contaminants detected in the final treated effluent. Overall, the results do not support the hypothesis that transition from a Kraft pulping to a dissolving pulping process significantly altered the bioactive contaminant loading from this particular WWTP to the St. Louis River Area of Concern.