Comparative assessment of energy generation from ammonia oxidation by different functional bacterial communities

• Published in: The Science of the total environment 2023-04, Vol.869, p.161688-161688, Article 161688
• Main Authors: Cano, Vitor, Nolasco, Marcelo A., Kurt, Halil, Long, Chenghua, Cano, Julio, Nunes, Sabrina C., Chandran, Kartik
• Format: Article
• Language: English
• Subjects: ammonia; Ammonia - metabolism; anaerobic ammonium oxidation; anodes; Anodophilic nitrification; Bacteria - metabolism; Bioelectrochemical system; biofilm; Biofilms; Bioreactors - microbiology; Circular economy; dissolved oxygen; energy balance; environment; genes; Green technologies; microbial fuel cells; Nitrification; nitrites; Nitrites - metabolism; Nitrogen - metabolism; organic carbon; oxidation; Oxidation-Reduction; potential energy; RNA, Ribosomal, 16S; sulfates; Waste-to-energy; wastewater treatment; Wastewater treatment plant
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.161688

Bioelectrochemical ammonia oxidation (BEAO) in a microbial fuel cell (MFC) is a recently discovered process that has the potential to reduce energy consumption in wastewater treatment. However, level of energy and limiting factors of this process in different microbial groups are not fully understood. This study comparatively investigated the BEAO in wastewater treatment by MFCs enriched with different functional groups of bacteria (confirmed by 16S rRNA gene sequencing): electroactive bacteria (EAB), ammonia oxidizing bacteria (AOB), and anammox bacteria (AnAOB). Ammonia oxidation rates of 0.066, 0.083 and 0.082 g NH4+-N L−1 d−1 were achieved by biofilms enriched with EAB, AOB, and AnAOB, respectively. With influent 444 ± 65 mg NH4+-N d−1, nitrite accumulation between 84 and 105 mg N d−1 was observed independently of the biofilm type. The AnAOB-enriched biofilm released electrons at higher potential energy levels (anode potential of 0.253 V vs. SHE) but had high internal resistance (Rint) of 299 Ω, which limits its power density (0.2 W m−3). For AnAOB enriched biofilm, accumulation of nitrite was a limiting factor for power output by allowing conventional anammox activity without current generation. AOB enriched biofilm had Rint of 18 ± 1 Ω and yielded power density of up to 1.4 W m−3. The activity of the AOB-enriched biofilm was not dependent on the accumulation of dissolved oxygen and achieved 1.5 fold higher coulombic efficiency when sulfate was not available. The EAB-enriched biofilm adapted to oxidize ammonia without organic carbon, with Rint of 19 ± 1 Ω and achieved the highest power density of 11 W m−3. Based on lab-scale experiments (scaling-up factors not considered) energy savings of up to 7 % (AnAOB), 44 % (AOB) and 475 % (EAB) (positive energy balance), compared to conventional nitrification, are projected from the applications of BEAO in wastewater treatment plants. [Display omitted] •Electrogen, AOB and anammox biofilms achieved different power levels in MFCs.•Electrogen rich biofilm adapted to oxidize ammonia and yielded highest power.•Nitrite accumulation was observed without known nitrifying bacteria presence.•O2 and SO42− are limiting factors for current generation by AOB.•N-NH4+ oxidation by anodophilic bacteria was combined with cathodophilic activity.