An integrated technology for efficient selenium remediation

Selenium is a metalloid that is utilized in the manufacturing of various industrial products including glasses, pigments, photovoltaic cells, and semiconductor devices. In recent years, the contamination of surface water systems and groundwater aquifers by selenium (Se) has become a critical problem in the United States and worldwide. In natural waters, Se predominantly exists as selenate (SeO42-) and selenite (SeO42-) oxyanion species which are both highly soluble and toxic.

Although selenium (Se) is an essential micronutrient for human health due to its antioxidant properties, chronic exposure to excess Se can adversely impact ecosystem health causing mutations and reproductive impairments in fish and aquatic invertebrates as toxic Se oxyanions bioaccumulate in aquatic food chains. The overarching goal of this project is to explore the design, evaluation, and optimization of a new integrated treatment train that can extract toxic selenate/selenite oxyanions from contaminated water and reduce them to elemental selenium (Se0) which is non-toxic and non-soluble.

To advance this goal, the Principal Investigators (PIs) propose to test the integration of a flow-electrode capacitive deionization (FCDI) ion separation process with a bioelectrochemical system (BES) into a compact reactor to remove, reduce, and detoxify selenate/selenite oxyanions from contaminated wastewater streams using electricity as driving force and power source. The successful completion of this project will benefit society through the generation of new fundamental knowledge and data to advance the design and deployment of more efficient and cost-effective technologies that could remove Se from industrial and contaminated wastewater streams prior to their discharge into receiving water bodies.

Additional benefits to society will be achieved through student education and training including the mentoring of a post-doctoral research fellow, one graduate student, and one undergraduate student at the University of Alabama.

Conventional and commercially available water treatment technologies (e.g., coagulation/precipitation, ion exchange, and reverse osmosis) cannot simultaneously remove toxic selenate/selenite oxyanions from contaminated water and convert them to non-toxic and insoluble zero valent selenium (Se0). In this project, the Principal Investigators (PIs) propose to test the hypothesis that the integration of a flow-electrode capacitive deionization (FCDI) ion separation process with a bioelectrochemical system (BES) into a compact reactor could enable the simultaneous removal, reduction, and conversion of toxic selenate/selenite oxyanions from contaminated wastewater to non-toxic Se0 using electricity as driving force and energy source.

The specific objectives of the research are to 1) characterize, evaluate, and optimize the performance of the integrated FCDI-BES reactor under relevant operating conditions using synthetic and real-world selenium contaminated wastewater; 2) probe and unravel the molecular mechanisms of the bioelectrochemical reduction of selenate/selenite oxyanions using metagenomic sequencing; and 3) conduct a life cycle analysis (LCA) and a global sensitivity analysis to guide the optimization of the performance of the proposed new and integrated FCDI-BES treatment train. To implement the education and training goals of this project, the PIs plan to recruit and mentor undergraduate students to work on the project research activities.

In addition, the PIs propose to leverage existing programs at the University of Alabama to design and deliver two annual educational activities consisting of immersive lab demonstrations for 30-50 high school students and teachers selected from over 120 schools located in the Alabama Black Belt, a region in the State of Alabama with persistent economic and social challenges including high poverty and high unemployment.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.