Forschungsdaten – Titel und Zusammenfassungen von Publikationen, extrahierte Daten und Katalogeinträge – erscheinen in ihrer Originalsprache Englisch.
Power Generation by Halophilic Bacteria and Assessment of the Effect of Salinity on Performance of a Denitrifying Microbial Fuel Cell
Ankisha Vijay, Prakash C. Ghosh, Suparna Mukherji
KI-Zusammenfassung
78 % KonfidenzThis study operated a dual-chamber MFC with halophilic bacteria at the anode oxidizing acetate in saline wastewater (20–40 g/L NaCl) and denitrifying bacteria at the cathode reducing NO₃⁻-N (345 mg/L initial). Power density increased 1.7-fold from 96.77 to 162.09 mW/m² as salinity rose from 20 to 40 g/L, accompanied by improved COD removal (76→83%) and NO₃⁻-N removal (80→89%). Electrochemical analysis showed charge transfer resistance decreased from 20 to 16 Ω with higher salinity, enabling faster electron transfer. Coulombic efficiency remained low (12–14%), indicating substantial substrate loss to non-electricity pathways. The system successfully coupled organic oxidation with autotrophic denitrification under closed-circuit conditions.
Zentrale Erkenntnisse
Schwellenwert Increasing anode salinity from 20 to 40 g/L NaCl raised power density 1.7-fold (96.77→162.09 mW/m²) and reduced charge transfer resistance from 20 to 16 Ω, indicating ionic strength directly enhances electron transfer kinetics in halophilic biofilms.
Was heißt das. Operators treating saline wastewater should target 40 g/L NaCl or higher to maximize power output, but must verify that the halophilic inoculum source tolerates the intended salinity range.
Zielkonflikt COD removal rate increased from 550 to 625 mg/L/d (13.6% gain) when salinity rose from 20 to 40 g/L, but coulombic efficiency remained low at 12–14%, meaning 86–88% of substrate was consumed by non-exoelectrogenic pathways.
Was heißt das. Higher salinity improves power output but does not proportionally improve substrate-to-electron conversion; operators should not assume that salinity optimization will reduce organic loading requirements.
Mechanismus Nitrate removal improved from 80±3% to 89±3.2% (NO₃⁻-N basis) as salinity increased from 20 to 40 g/L, with removal rate rising from 110±4 to 124±3 mg/L/d, correlating directly with higher cathode current.
Was heißt das. Denitrification rate in bioelectrochemical cathodes is current-limited; operators should prioritize anode-side conditions (salinity, substrate) that maximize current density to achieve target nitrate removal rates.
Mechanismus Under open-circuit conditions, COD removal was only 28–32%, versus 76–83% under closed-circuit operation, demonstrating that electrons channeled to the electrode drive organic oxidation.
Was heißt das. Closed-circuit operation is essential for efficient COD removal in this system; open-circuit or high-resistance modes will severely limit wastewater treatment performance.
Methode Cyclic voltammetry showed oxidative peak current increased 1.7-fold (27.68→46.54 mA) at 40 g/L salinity, and reductive peak current increased 1.8-fold (−34.31→−62.97 mA), indicating higher biofilm electrochemical activity at elevated salinity.
Was heißt das. Salinity enhancement of biofilm electroactivity is measurable via CV; use CV as a diagnostic tool to confirm that halophilic enrichment is responding to salinity changes.
Ansatzpunkte6
Konkrete Lücken in dieser Publikation, jeweils mit einem Experiment, das sie schließen würde.
Hoch No measurement of N₂O or NO₂⁻ accumulation during denitrification; incomplete nitrogen mass balance.
Paper reports NO₃⁻-N removal (80–89%) but does not quantify end products or intermediate accumulation. Section 3.4 states 'autotrophic denitrification' but provides no gas chromatography or ion chromatography data for N₂O, NO, or NO₂⁻. This is critical for assessing whether the cathode is a complete denitrifier or a partial denitrifier.
Versuch. Measure N₂O, NO, NO₂⁻, and N₂ via gas chromatography and ion chromatography across both salinity conditions; quantify nitrogen recovery to close mass balance.
Hoch No systematic variation of cathode potential or applied voltage; operating window for denitrification not defined.
Paper operated MFC at fixed 100 Ω external resistance and did not sweep cathode potential or apply external voltage. Section 3.4 notes that 'higher nitrate removal was caused by higher current' but does not isolate the effect of cathode potential (which drives denitrification kinetics) from anode potential (which drives current). Optimal cathode potential for complete denitrification vs. partial denitrification is unknown.
Versuch. Vary cathode potential from −0.2 to −0.8 V vs. Ag/AgCl at fixed anode potential or fixed current; measure NO₃⁻-N removal, N₂O/NO₂⁻ accumulation, and current density.
Mittel No variation of hydraulic retention time (HRT) or feed cycle duration; substrate depletion kinetics and limiting conditions not characterized.
All experiments used 4-day fed-batch cycles with fixed initial COD (2900 mg/L) and NO₃⁻-N (345 mg/L). Section 3.1 shows voltage drops when acetate depletes, but no systematic study of how HRT affects COD removal rate, nitrate removal rate, or N₂O formation.
Versuch. Operate at 2, 4, 6, and 8-day cycle lengths at both salinities; measure COD removal rate, NO₃⁻-N removal rate, and N₂O accumulation to identify optimal HRT window.
Mittel No measurement of catholyte pH or dissolved oxygen; cathode microenvironment not characterized.
Paper reports anolyte pH adjusted to 7.0±0.2 and catholyte pH adjusted to 7.0 initially, but does not monitor pH drift or dissolved oxygen during operation. Denitrification is pH-sensitive and can be inhibited by residual oxygen. Section 3.4 assumes autotrophic denitrification but does not verify anaerobic conditions or pH stability.
Versuch. Monitor catholyte pH and dissolved oxygen continuously during fed-batch cycles at both salinities; correlate with NO₃⁻-N removal rate and N₂O accumulation.
Mittel No variation of C/N ratio or initial NO₃⁻-N concentration; substrate limitation and electron acceptor limitation not distinguished.
Fixed initial NO₃⁻-N at 345 mg/L and initial COD at 2900 mg/L (C/N ≈ 10 on molar basis). Paper does not test whether denitrification is limited by electron availability (current) or by nitrate availability. Section 3.4 states nitrate was 'supplemented at regular intervals' but does not specify when or how much.
Versuch. Vary initial NO₃⁻-N from 100 to 500 mg/L at fixed COD (2900 mg/L) and fixed salinity (40 g/L); measure NO₃⁻-N removal rate and current density to identify electron acceptor limitation.
Mittel Coulombic efficiency is very low (12–14%); substrate fate and competing pathways not investigated.
Section 3.3 attributes low CE to 'microbial growth, non-electricity producing reactions, and formation of secondary microbial products' but provides no quantitative breakdown. No measurement of volatile fatty acids, biomass accumulation, or methane production.
Versuch. Perform carbon balance: measure biomass (MLVSS), volatile fatty acids (HPLC), and biogas composition (GC) to account for the 86–88% of substrate not converted to current.
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Was gemacht wurde
- Systemtyp
- MFC
Was funktioniert hat
Zusammenfassung
Saline wastewater pollution is a critical issue that needs to be addressed. The present study focused on the development of a dual-chambered microbial fuel cell (MFC) treating saline wastewater at the anode. Halophilic exo-electrogenic bacteria enriched from seawater (Arabian Sea, Mumbai, India) were used in the anodic chamber of the MFC. Denitrification using denitrifying bacteria was employed in the cathodic chamber. The maximum power density was significantly increased from 96.77 mW/m² to 162.09 mW/m² with a rise in NaCl concentration from 20 to 40 g/L. Nitrate removal in the cathode chamber increased from 80 ± 3% to 89 ± 3.2% with increase in salt concentration from 20 g/L to 40 g/L and concomitantly COD removal in the anode chamber increased from 76 ± 3.8% to 83 ± 4%. Cyclic voltammetry (CV) analysis revealed higher electrochemical activity at 40 g/L salt concentration. Electrochemical impedance spectroscopy (EIS) analysis exhibited that charge transfer and solution resistances were lower when the salinity was increased. Microbial community analysis revealed the presence of Clostridium, Shewanella, and Bacillus as the most abundant genera in the anodic chamber. This study demonstrated the dual applicability of the system targeted for removal of organics from saline wastewater and nitrate removal from contaminated wastewater accompanied by power generation from the MFC.
Schlagwörter
Kennungen
- Zeitschrift
- Energies
- Jahr
- 2023
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