PROJECT HIGHLIGHT:
Horizontal levees are nature-based wastewater treatment systems where subsurface microbes remove contaminants from wastewater or reverse osmosis concentrate (ROC). This research investigates how these systems process three trace metals (Ni, Cu, and Zn) through biogeochemical processes, aiming to determine if such systems can prevent them from being a potential source of contamination.
PROJECT SUMMARY:
Coastal communities require adaptation measures to minimize their risk from sea level rise. Protection is considered the most feasible approach in urbanized areas with limited space. A horizontal levee is a nature-based wastewater treatment system designed to protect coastal infrastructure from the effects of sea level rise, alongside the added benefits of improving water quality and providing habitat. A horizontal levee relies on microbes in the subsurface to create a distinct redox gradient capable of removing nutrients and pharmaceuticals from treated municipal wastewater and reverse osmosis concentrate (ROC).
This research is investigating the biogeochemical processes that govern the immobilization of toxic metals in horizontal levees and how these systems can be designed to target specific contaminants and prevent them from being a potential source of contamination. Involving stakeholders who are familiar with water quality criteria, environmental compliance and urban development ensures that the strategies created by the research team increase the feasibility and accessibility of this technology and support the development of resilient coastal communities.
Eight wetland cells have been constructed at Oro Loma Sanitary District in San Lorenzo. Throughout 2024, researchers monitored key parameters and extracted sediments for analysis. Though research is ongoing, early findings show that complete sulfate reduction took six months, after which copper was effectively removed in the wastewater cell. In the reverse osmosis concentrate cell, granular activated carbon enhanced copper removal. Notably, nickel showed different behavior, increasing in wastewater and porewater, while remaining stable in the ROC cell.
Community Mentor: Jeremy Lowe (San Francisco Estuary Institute)