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Colloidal and truly dissolved metal(loid)s in wastewater lagoons and their removal with floating treatment wetlands

Year: 2019
Type: dissertation
Abstract: 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.
Language: English
Open Access status: green
OpenAlex ID: W2955220595
Cites: 45
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Related to: 10