Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Systems Ecology

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Benjamin P. Colman

Commitee Members

Brian Chaffin, Lisa Eby, Marc Peipoch


element cycling, biogeochemistry, wastewater lagoons, floating treatment wetlands, clark fork river


University of Montana

Subject Categories

Applied Statistics | Biogeochemistry | Terrestrial and Aquatic Ecology | Water Resource Management


Climate change is predicted to cause continuing declines in late-season streamflow, thus increasing the relative contribution of wastewater effluent to surface water flows. Wastewater effluent represents a critical point source of metal and metalloid contamination to aquatic ecosystems and wastewater lagoons are the most common wastewater treatment system in the rural United States. Although the fraction of total wastewater metals and metalloids in "dissolved" forms (defined here asnm) likely drives the potential for negative effects on receiving waters, this broad operational definition lumps truly dissolved solutes (nm) with small colloids and nanomaterials (1-450 nm; hereafter colloids). This size distinction may be important as colloidal particles and truly dissolved solutes differ in their interactions with aquatic organisms and likely would require different strategies for their removal from wastewater. One potential tool for improving metal(loid) removal in wastewater lagoons is floating treatment wetlands, which consist of hydroponically grown plants on floating mats. This study examined the distribution of metal(loid)s between truly dissolved and small colloidal size fractions in six wastewater lagoon systems. Additionally, the efficacy of floating treatment wetlands in removing metal(loid)s and influencing the distribution of contaminants among truly dissolved and small colloidal size ranges was examined. In this survey of six lagoons, it was found that iron, lead, copper, manganese, and zinc were most abundant as small colloidal particles while aluminum, arsenic, and chromium were found mostly as truly dissolved solutes. The floating treatment wetlands were especially effective at removing those metal(loid)s that were abundant in colloidal forms, suggesting a potential role for floating treatment wetlands in enhancing wastewater lagoon efficiency for some metal(loid) contaminants.



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