Forschungsdaten – Titel und Zusammenfassungen von Publikationen, extrahierte Daten und Katalogeinträge – erscheinen in ihrer Originalsprache Englisch.
Enhanced low C/N nitrogen removal in an innovative microbial fuel cell (MFC) with electroconductivity aerated membrane (EAM) as biocathode
Yun Wu, Qing Yang, Qingnan Zeng, Huu Hao Ngo +2
KI-Zusammenfassung
78 % KonfidenzThis study couples an electroconductivity aerated membrane (EAM) biocathode with a microbial fuel cell (MFC) anode to achieve simultaneous nitrification–denitrification (SND) at low C/N ratio (2.89 g COD g⁻¹ NH₄⁺-N). Operating at 5 Ω external resistance and 0.2–0.5 mg L⁻¹ dissolved oxygen, the system achieved 80.81% total nitrogen removal (0.128 kg TN m⁻³ d⁻¹), 94.73% COD removal, and 4.20 W m⁻³ power density. Electrochemical denitrification improved TN removal by 19.80% versus open circuit, with cathode coulombic efficiency reaching 42.84% for NO₃⁻-N reduction. The controlled aeration in the EAM prevented oxygen diffusion to the anode, enabling higher anode coulombic efficiency (40.67%) than prior MFC–MBR systems.
Zentrale Erkenntnisse
Zielkonflikt Decreasing external resistance from 100 Ω to 5 Ω increased current density from 0.36 to 4.10 A m⁻² and improved TN removal efficiency from ~60% to 80.81%, demonstrating that higher electron flux drives electrochemical denitrification.
Was heißt das. Operators should minimize external resistance to maximize current density when the goal is nitrogen removal; however, this trades off against power density, which peaked at 10 Ω (4.20 W m⁻³).
Schwellenwert Nitrite accumulated from barely detectable to 2.32 mg L⁻¹ as external resistance decreased and current increased, indicating incomplete reduction of NO₃⁻ to N₂ under high electron flux.
Was heißt das. Operators must monitor and control cathode potential or current density to avoid NO₂⁻ accumulation; intermediate products suggest incomplete denitrification kinetics or electron acceptor competition.
Mechanismus Maintaining cathode dissolved oxygen at 0.2–0.5 mg L⁻¹ prevented oxygen diffusion to the anode, achieving anode coulombic efficiency of 40.67% at 5 Ω, substantially higher than prior MFC–MBR systems (1.5–21%).
Was heißt das. Use membrane aeration with tight DO control (0.2–0.5 mg L⁻¹) to prevent oxygen crossover; this design choice is critical for maintaining anode efficiency in coupled MFC–MABR systems.
Leistung The system achieved COD/N ratio of 2.89 g COD g⁻¹ NH₄⁺-N, lower than traditional MABR (5 g COD g⁻¹ NH₄⁺-N) and comparable to advanced sequencing batch reactors (2–3 g COD g⁻¹ TN), despite only 19.80% improvement from electrochemical denitrification versus open circuit.
Was heißt das. This system is suitable for low-C/N wastewaters; however, the modest 19.80% improvement suggests that bioelectrochemical denitrification alone cannot fully compensate for carbon limitation—hybrid approaches or external electron donors may be needed.
Mechanismus Cathode potential remained at maximum 0.18 V vs SHE, well below the standard potentials for O₂ (0.805 V), NO₃⁻ (0.433 V), and NO₂⁻ (0.350 V) reduction, indicating large overpotential losses and energy inefficiency at the cathode.
Was heißt das. Cathode overpotential is a major loss mechanism; improving cathode kinetics (biofilm composition, electrode material, or mediators) should be prioritized to increase power output and denitrification rate.
Ansatzpunkte6
Konkrete Lücken in dieser Publikation, jeweils mit einem Experiment, das sie schließen würde.
Hoch No systematic study of cathode potential vs current density relationship; cathode potential remained at 0.18 V vs SHE across all loads, suggesting it may be limited by biofilm kinetics or mass transfer rather than electrochemistry.
Authors note 'large energy loss occurred at the cathode' and attribute it to overpotential, intermediate products (NO₂, N₂O), and microbial maintenance, but do not vary cathode potential independently or measure N₂O.
Versuch. Potentiostatic control of cathode at 0.0, −0.1, −0.2, −0.3 V vs SHE; measure NO₂⁻ and N₂O accumulation; quantify electron recovery to N₂ vs N₂O.
Hoch No measurement of N₂O production or quantification of N₂ as final product; nitrogen balance incomplete.
Authors assume N₂ is the final product in coulombic efficiency calculation (Eq. 4, n=5 for NO₃⁻) but provide no gas chromatography or isotope data. Nitrite accumulation (2.32 mg L⁻¹) suggests incomplete reduction; N₂O may be produced.
Versuch. Gas-phase sampling (GC-ECD or IRMS) for N₂O and N₂; nitrogen balance closure; test at different cathode potentials and DO levels.
Mittel Aeration intensity tested at only two levels (30 kPa, 20 kPa); no systematic optimization of DO setpoint for SND vs power generation trade-off.
Authors state 'The dissolved oxygen of the cathode liquor was controlled at 0.2-0.5 mg L⁻¹ throughout the study' but Table 1 shows only two aeration pressures tested, with minimal difference in anode CE (0.34% decrease). Optimal DO window for SND is known to be 0.3–0.8 mg L⁻¹ from prior work (Munch, Pochana–Keller cited).
Versuch. Vary DO setpoint from 0.1 to 1.0 mg L⁻¹ in 0.1 mg L⁻¹ increments; measure TN removal, power density, NO₂⁻ and N₂O accumulation at each level.
Mittel No investigation of HRT effect on nitrogen removal and electrochemical denitrification; only one HRT (12 h) tested.
HRT is a critical operating parameter for SND and biofilm kinetics. Authors operated at fixed 12 h HRT; no data on shorter (6–8 h) or longer (18–24 h) retention times.
Versuch. Test HRT 6, 9, 12, 15, 18 h at constant current density (e.g., 4 A m⁻²); measure TN removal rate, NO₂⁻ accumulation, and biofilm thickness.
Mittel No characterization of biofilm composition or microbial community; mechanisms of SND inferred but not verified.
Authors propose layered biofilm with nitrifiers in inner aerobic zone and denitrifiers in outer anaerobic zone (Fig. 6), but provide no microscopy, 16S rRNA, or functional gene data.
Versuch. FISH or 16S rRNA sequencing of cathode biofilm at different depths; quantify nitrifier and denitrifier abundance; correlate with NO₂⁻ accumulation and current density.
Niedrig C/N ratio in influent is fixed at 2.8 g COD g⁻¹ N; no variation to test the claimed 'low C/N' capability or identify the minimum C/N at which the system fails.
Authors claim advantage at 'low COD/N ratio of 2.8' but do not test lower ratios (e.g., 1.5, 1.0) or higher ratios (e.g., 4, 5) to establish operating window.
Versuch. Vary influent C/N from 1.0 to 5.0 g COD g⁻¹ N; measure TN removal efficiency, NO₂⁻ accumulation, and power density; identify threshold below which performance degrades.
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Was gemacht wurde
- Systemtyp
- MFC
Was funktioniert hat
Schlagwörter
Kennungen
- Zeitschrift
- Chemical Engineering Journal
- Jahr
- 2016
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