Harnessing the Novel Acidimicrobiaceae sp. Strain A6: Optimal Environmental and Operational Conditions in Constructed Wetland Mesocosms and Microbial Electrochemical System

Abstract

The anaerobic ammonium oxidation coupled iron reduction, which is known as the Feammox process, can be carried out by a recently identified and isolated bacterium named Acidimicrobiaceae sp. strain A6 (A6). As an autotrophic, iron-reducing bacterium, A6 has shown versatility in using different electron acceptors while extracting energy through ammonium oxidation under anaerobic conditions. The unique characteristics of A6 open up multiple directions for application. An early attempt of the application was done in constructed wetland (CW) mesocosms, where anaerobic ammonium removal was enhanced and A6 numbers were enriched by providing favorable conditions with an elevated level of ferric iron in the constructed wetland mesocosm sediments. In addition, both laboratory and field experiments have shown that A6 can colonize the electrodes inserted in the wetland sediments and is associated with current production in the CW mesocosms. This finding leads to the application of A6 in microbial electrochemical systems such as microbial electrolysis cells (MECs) and microbial fuel cells (MFCs). A recent groundbreaking discovery in the research group revealed that bacterium A6 has the ability to defluorinate per- and polyfluoroalkyl substances (PFAS) including perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Results from A6-inoculated MECs are promising, showing significant PFOA removal and intermediates production after 18 days of operation. Exploration of the operational conditions in the continuous-flow MEC reactor designed for A6 has shown promising directions for further research. Findings from this dissertation can be instructive for future studies on the optimization of reactor design, relationship between A6 and other microorganisms, and the mechanisms of defluorination by A6 in incubations, MECs, and CW mesocosms.