NSF Award
2327516
Wastewater treatment plants (WWTPs) play a critical role in environmental protection. In the United States, municipal WWTPs process billions of gallons of wastewater every day to remove suspended solids, organic matter, and excess nitrogen nutrients such as ammonium. In most municipal WWTPs, a biological process, activated sludge (AS), is used to remove nitrogen by coupling an aerobic nitrification process which oxidizes ammonium into nitrate followed by an anaerobic denitrification process that reduces the nitrate to benign dinitrogen gas (N2). However, ammonium nitrification in AS reactors requires the supply of oxygen using aeration which requires a significant amount of energy and accounts for 70-80 % of the total energy used in WWTPs. Anaerobic ammonium oxidation (anammox) has emerged as a promising microbial process for removing nitrogen from municipal wastewater with lower energy consumption and operating costs. However, the selection, cultivation, and integration of anammox bacteria into reactors and the treatment trains of municipal WWTPs has remained a challenge due to their slow growth rates and competition from other microorganisms including ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Recent studies show that anammox microbes can generate electricity. Building upon these promising studies, the Principal Investigators (PIs) of this project propose to explore the selection of electroactive anammox bacteria using bioelectrochemical systems with the goal of accelerating their growth, proliferation, and stability in municipal wastewater. The successful completion of this project will benefit society through the generation of fundamental knowledge in environmental microbiology and biotechnology to advance the development and deployment of more cost-effective solutions for nitrogen removal from municipal and industrial wastewater. Additional benefits to society will be achieved through student education and training including the mentoring of one graduate student at Temple University and one graduate student at the University of Maryland.<br/><br/>Anaerobic ammonium oxidation (anammox) bacteria have recently been shown to perform extracellular electron transfer (EET), but little is known about the mechanisms through which anammox bacteria transfer electrons extracellularly to electrodes, and even less is known about how electrons are transported intracellularly from the anammoxosome to the outer membrane proteins for downstream EET. The overarching goal of this project is to advance the fundamental understanding of the microbial ecology and ecophysiology of electroactive anammox communities in bioelectrochemical systems (BES). The core and guiding hypothesis of the proposed research is that in BES, EET-dependent anammox is carried out by a microbial population composed of electroactive anammox bacteria and their electroactive partners. Together they form a mutualistic relationship: anammox bacteria fix carbon dioxide and provide organic matter to electroactive bacteria, whose electron shuttles are scavenged by anammox bacteria for EET. If the hypothesis holds, EET-dependent anammox could be electrochemically enhanced through the enrichment of those two partners. The specific aims of the research are to 1) develop electrochemical strategies to build electroactive anammox communities; 2) understand the microbial interactions in electroactive anammox communities; and 3) elucidate the metabolic pathways involved in EET-dependent anammox. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge on the microbial ecology and ecophysiology of electroactive anammox microbiomes in BES to guide the design and implementation of more sustainable technologies and solutions to remove nitrogen from municipal and industrial wastewater. To implement the education and training goals of the project, the PIs propose to leverage existing programs at Temple University (TU) and the University of Maryland (UMD) to recruit and mentor undergraduate students from underrepresented groups to work on the project. In addition, the PIs plan to integrate the findings from this research into existing environmental engineering graduate/undergraduate courses at TU and UMD.<br/><br/>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.
