Fe(0)-Dissimilatory Nitrate Reduction to Ammonium for Autotrophic Recovery of Reactive Nitrogen
Yue Wu1, Baocai Zhang2, Yuxuan Wan1
1MOE Key Laboratory of Pollution Processes and Environmental Criteria/Tianjin Key Laboratory of Environmental Remediation and Pollution Control/College of Environmental Science and Engineering, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China.
Abstract:
Bioreduction of nitrate to value-added ammonium is a potentially sustainable strategy to recycle nutrients from wastewater. Here, we have proven the feasibility of the reduction of autotrophic nitrate to ammonium with electrons extracted from Fe(0). Using a Geobacter-dominated anodic biofilm as an inoculum, we achieved nitrate-to-ammonium efficiency up to 90 ± 3% with a nitrate reduction rate of 35 ± 1.3 mg N/d/L. An electron acceptor instead of an inoculum greatly influenced the Fe(0)-dissimilatory nitrate reduction to ammonium (DNRA), where nitrite as the electron acceptor provided an effective selective pressure to enrich Geobacter from initial 5 to 56%. The DNRA repressing denitrification was demonstrated by the reverse tendencies of upregulated nrfA and downregulated nirS gene transcription. This finding provides a new route for autotrophic nitrate removal and recycling from water, which has a broader implication on biogeochemical nitrogen and iron cycling.
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