Performance and mechanism of concurrent nitrogen elimination and arsenite oxidation/detoxification in a membrane aerated biofilm reactor system

The concurrent presence of nitrogen and arsenite [As(III)] in wastewater poses a significant environmental challenge. Herein, a continuous flow membrane aerated biofilm reactor (MABR) system was developed to fulfil simultaneous nitrification and denitrification (SND) and As(III) oxidation for the first time. Nitrogen, carbon and As metabolism mechanism, microbe functional groups properties, as well as microbial compositions and functional genes were documented. Results indicated that the SND and As(III) oxidation efficiency reached 73.40 +/- 4.33 % and 99.42 +/- 0.11 %, even when influent As(III) concentration increased to 400 mg/L. As(III) oxidized to As(V), which corroborated that As(III) oxidation was the pivotal detoxification pathway. Carbohydrate (C-O), carboxyl (O-C--O) and hydroxyl (-OH) on the surface of biofilm played a major role in the binding and adsorption of As(V). Unidentified Nitrospiraceae, Denitratisoma and Hydrogenophaga were putative microbes pertaining to nitrogen, carbon and As metabolism under high As(III) stress. Autotrophic combined heterotrophic metabolism played a potential role for enhanced nitrogen removal. Indeed, the abundance of genes connected with nitrogen, carbon and As transformation and metabolism upregulated remarkably with the increase of the influent As(III) concentration. This work indicated MABR had great applications potential in synchronous nitrogen elimination and As(III) oxidation/detoxification.