The Living Levee is a constructed subsurface-flow wetland that receives effluent from the Oro Loma Sanitary District located in San Lorenzo, California. It was designed to improve coastal levees by replacing traditional grey infrastructure with natural sloped marshes. This new design aims to reduce costs for maintenance and energy and also provide key ecosystem services that would ultimately benefit the area. With respect to water quality improvement, the original purpose of the wetland was to encourage nitrate removal through denitrification. However, researchers found the wetland was also able to reduce the concentrations of a number of trace organic contaminants (TrOCs), which are a diverse and expanding array of natural and anthropogenic substances including industrial chemicals, chemicals used in households, compounds and their metabolites excreted by people and by-products formed during wastewater and drinking-water treatment processes. Past studies have suggested that the reduction in concentration of these compounds is mostly due to biotransformation, in which microbial activity results in structural alterations of TrOCs and formation of metabolites. However, the exact mechanism of biotransformation is difficult to study under field conditions. The objective of this study is to design a microcosm that can accurately simulate the conditions and pharmaceutical transformations seen in the wetland, ensuring that the most accurate bench-scale measurements can be made.<br/>In order to simulate the conditions of the wetland, soil and porewater samples were taken directly from the field for use in the microcosms. The samples were taken near the inlet of the wetland, where removal of the pharmaceuticals is primarily observed. Microcosms were constructed using 20 mL scintillation vials, ~45 g of soil, and ~2 mL of porewater. The porewater was spiked with a solution of 13 pharmaceuticals of known concentration so that change in concentration could be measured over time. After comparing data collected from the microcosms and from the wetland, it was found that trends were not quite the same. The decreases in concentrations seen in the microcosms were mostly attributed to sorption to soil rather than microbial transformation.

Simulating microbial transformation of pharmaceuticals in subsurface wetlands on the bench-scale

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.