Forschungsdaten – Titel und Zusammenfassungen von Publikationen, extrahierte Daten und Katalogeinträge – erscheinen in ihrer Originalsprache Englisch.
The Denitrification Characteristics and Microbial Community in the Cathode of an MFC with Aerobic Denitrification at High Temperatures
Jianqiang Zhao, Jinna Wu, Xiaoling Li, Sha Wang +2
KI-Zusammenfassung
82 % KonfidenzThis study demonstrates that dissolved oxygen concentration is a critical control parameter in bioelectrochemical cathodes for simultaneous nitrification–denitrification (SND) of high-ammonia wastewater at elevated temperatures (36–48 °C). At low DO (0.5–1.0 mg/L), heterotrophic denitrifiers dominate and achieve higher total nitrogen removal (~14 mg/(L·d)) but lower voltage. At high DO (3.0–4.2 mg/L), aerobic denitrifying bacteria (ADB) become dominant, producing higher voltage (~100 mV) and N₂O emissions, with electrode-driven denitrification contributing 8.5–14.6 mg N/(L·d) depending on external resistance. Lowering external resistance from 100 Ω to 50 Ω increases electrode denitrification rate and N₂O production, revealing a trade-off between power output and nitrogen removal pathway.
Zentrale Erkenntnisse
Zielkonflikt At high DO (3.0–4.2 mg/L), electrode denitrification by ADB produces 13.5–14.6 mg N/(L·d) with 50 Ω resistance versus 8.5–9.0 mg N/(L·d) with 100 Ω, showing that lower external resistance drives higher electrode-catalyzed denitrification.
Was heißt das. Operators targeting maximum electrode-driven nitrogen removal should minimize external resistance, but this increases N₂O slip (10% of nitrogen removed becomes N₂O rather than N₂).
Zielkonflikt Heterotrophic denitrification at low DO (0.5–1.0 mg/L) removes ~14 mg TN/(L·d) total, but electrode denitrification contributes only ~7 mg/(L·d), meaning COD-driven heterotrophic pathways dominate nitrogen removal at low oxygen.
Was heißt das. If nitrogen removal is the priority and carbon is available, maintain low DO and intermittent aeration to favor heterotrophic denitrifiers over electrode denitrification, accepting lower voltage output.
Mechanismus Increasing DO from 0.5–1.0 to 3.0–4.2 mg/L shifts the dominant microbial community from Firmicutes (Ureibacillus, Bacillus, Anoxybacillus) to Proteobacteria (Aquamicrobium, Brachymonas, Comamonas), enabling aerobic denitrification but reducing total heterotrophic denitrification capacity.
Was heißt das. Design cathode aeration strategy around desired microbial community: low DO favors thermophilic heterotrophic denitrifiers; high DO selects for aerobic denitrifiers with electrode-coupling capability.
Schwellenwert N₂O production increases with temperature and is independent of electrode potential at 100 Ω resistance (0.7–1.1 mg/L N₂O across all conditions), but becomes electrode-dependent at 50 Ω resistance, with ~10% of nitrogen removed converted to N₂O.
Was heißt das. Minimize N₂O emissions by avoiding low external resistance (<50 Ω) during high-DO operation, or accept N₂O as a byproduct of efficient electrode denitrification.
Mechanismus At C/N ratio ≤0.3 (COD 300 mg/L, NH₄⁺-N 480 mg/L), electrode denitrification by ADB provides sufficient electrons to sustain nitrogen removal without heterotrophic carbon oxidation, enabling nitrogen removal independent of organic substrate availability.
Was heißt das. In high-ammonia, low-carbon wastewaters (e.g., sludge digestion liquor), electrode-driven denitrification can be the primary nitrogen removal mechanism if high DO and low external resistance are maintained.
Ansatzpunkte6
Konkrete Lücken in dieser Publikation, jeweils mit einem Experiment, das sie schließen würde.
Mittel No systematic variation of external resistance between 50 and 100 Ω to map the transition point where electrode denitrification becomes the dominant pathway and N₂O production becomes electrode-dependent.
The paper tests only 50 Ω and 100 Ω; intermediate resistances (60, 70, 80, 90 Ω) would reveal the threshold for switching from heterotrophic to electrode-driven denitrification.
Versuch. Vary external resistance in 10 Ω increments from 50–100 Ω; measure electrode potential, N₂O concentration, TN removal rate, and dominant microbial species at each resistance.
Hoch No investigation of cathode potential (vs. SHE or Ag/AgCl) as an independent control variable; only external resistance is varied, which indirectly controls potential.
The paper measures anode potential (Figure 3D, 4D) but does not report cathode potential. Cathode potential directly determines which nitrogen species (NO₃⁻, NO₂⁻, N₂O, N₂) are thermodynamically favored for reduction.
Versuch. Potentiostat the cathode at fixed potentials (e.g., −0.2, −0.4, −0.6, −0.8 V vs. SHE) while maintaining high DO and measuring N₂O, NO₂⁻, and TN removal rates to identify the potential window for selective N₂O or N₂ production.
Mittel No measurement of nitrite (NO₂⁻-N) accumulation in the cathode effluent during high-DO, low-resistance operation, despite evidence that electrode denitrification is occurring.
Figure 2 shows NO₂⁻-N in the effluent but does not report its concentration during stage 4 (high DO, 50 Ω). Nitrite accumulation is a sign of incomplete denitrification and a potential environmental concern.
Versuch. Measure NO₂⁻-N, NO₃⁻-N, and N₂O simultaneously during stage 4 at 50 Ω and 100 Ω to quantify the nitrogen speciation and identify whether nitrite is being accumulated or recycled.
Mittel No exploration of catholyte pH effects on aerobic denitrification or N₂O production, despite pH being a known regulator of denitrification enzyme activity.
The paper does not report pH during stages 3–4 (high DO). Aerobic denitrification enzymes have pH optima that may differ from anaerobic denitrification, affecting N₂O yield.
Versuch. Vary catholyte pH (6.5–8.5) at high DO and 50 Ω resistance; measure N₂O production, electrode potential, and dominant ADB species to identify the pH window minimizing N₂O slip.
Niedrig No testing of lower C/N ratios (<0.3) to confirm the lower bound at which electrode denitrification can sustain ADB without heterotrophic carbon.
The paper states that ADB survive at C/N ≤0.3 but tests only one ratio (0.3). Lower ratios would test the limit of electrode-driven nitrogen removal.
Versuch. Reduce influent COD to 100–150 mg/L (C/N 0.1–0.15) while maintaining 480 mg/L NH₄⁺-N and high DO; measure TN removal rate and ADB abundance to confirm the minimum C/N for sustained denitrification.
Niedrig No comparison of electrode materials (carbon brush vs. felt, graphite, stainless steel) on ADB enrichment and N₂O production at high DO.
The paper uses only carbon brush electrodes. Different materials have different electron transfer kinetics and surface properties that may favor different ADB species or N₂O pathways.
Versuch. Replace carbon brush with carbon felt or graphite felt at identical operating conditions (high DO, 50 Ω, 36–48 °C); measure electrode potential, N₂O, TN removal, and microbial community composition.
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Was gemacht wurde
- Systemtyp
- MFC
Was funktioniert hat
Zusammenfassung
Microbial fuel cells (MFCs) have attracted much attention due to their ability to generate electricity while treating wastewater. The performance of a double-chamber MFC with simultaneous nitrification and denitrification (SND) in the cathode for treating synthetic high concentration ammonia wastewater was investigated at different dissolved oxygen (DO) concentrations and high temperatures. The results showed that electrode denitrification and traditional heterotrophic denitrification co-existed in the cathode chamber. Electrode denitrification by aerobic denitrification bacterium (ADB) is beneficial for achieving a higher voltage of the MFC at high DO concentrations (3.0-4.2 mg/L), while traditional heterotrophic denitrification is conducive to higher total nitrogen (TN) removal at low DO (0.5-1.0 mg/L) concentrations. Under high DO conditions, the nitrous oxide production and TN removal efficiency were higher with a 50 Ω external resistance than with a 100 Ω resistance, which demonstrated that electrode denitrification by ADB occurred in the cathode of the MFC. Sufficient electrons were inferred to be provided by the electrode to allow ADB survival at low carbon:nitrogen ratios (≤0.3). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) results showed that increasing the DO resulted in a change of the predominant species from thermophilic autotrophic nitrifiers and facultative heterotrophic denitrifiers at low DO concentrations to thermophilic ADB at high DO concentrations. The predominant phylum changed from Firmicutes to Proteobacteria , and the predominant class changed from Bacilli to Alpha, Beta , and Gamma Proteobacteria .
Schlagwörter
Kennungen
- PubMed
- 28154554
- Zeitschrift
- Frontiers in Microbiology
- Jahr
- 2017
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