Forschungsdaten – Titel und Zusammenfassungen von Publikationen, extrahierte Daten und Katalogeinträge – erscheinen in ihrer Originalsprache Englisch.
Effects of Carbon Source on Denitrification and Electricity Generation in Composite Packing MFC-CW for Tail Water Treatment
Yu Kong, Jing Hu, Xiwu Lü, Changgen Cheng
KI-Zusammenfassung
78 % KonfidenzThis study integrated a microbial fuel cell (MFC) with a constructed wetland (CW) using HDPE fillers to treat low-carbon tail wastewater. The MFC-CW system achieved 73.91% total nitrogen removal in steady state, outperforming standalone CW (63.88%) and MFC (68.65%). Nitrogen removal improved with increasing C/N ratio up to 8, but power output remained insensitive to COD variation between 40–120 mg/L. The bioelectrochemical coupling reduced carbon-source dependence for denitrification compared to passive wetlands, making it suitable for nutrient-limited secondary effluent polishing.
Zentrale Erkenntnisse
Leistung MFC-CW achieved 73.91% TN removal versus 63.88% in CW alone during steady state, a 10 percentage-point gain driven by electrochemical enhancement of denitrification.
Was heißt das. Integrate electrodes into wetlands treating low-carbon effluent to recover 10+ percentage points of nitrogen removal without adding external carbon.
Schwellenwert NO₃⁻-N removal reached nearly 100% when C/N ≥ 4, but at C/N = 2.67 denitrification was severely limited, indicating a threshold below which carbon becomes rate-limiting.
Was heißt das. Operate MFC-CW systems at C/N ≥ 4 to avoid NO₃⁻-N accumulation; below this threshold, supplement carbon or rely on electrochemical reduction at the cathode.
Zielkonflikt CW TN removal increased 35.8 percentage points (50.08% → 85.88%) when C/N rose from 2.67 to 5.33, while MFC-CW increased only 16.5 points (57.28% → 73.77%), showing MFC-CW is 2.2× less carbon-dependent.
Was heißt das. Use MFC-CW for low-C/N wastewaters (2.67–4) where passive CW fails; the electrochemical pathway supplies electrons for denitrification independent of organic carbon.
Schwellenwert Output voltage and power density showed minimal response to COD increase from 40–120 mg/L (average ~100 mV, max power 0.23–0.83 mW/m²), indicating power is not limited by carbon in this low-load regime.
Was heißt das. Do not expect power output to scale with carbon addition in low-COD tail waters; focus on electrode kinetics and internal resistance (1150–2211 Ω) rather than substrate availability.
Zielkonflikt Water hyacinth planting reduced MFC-CW power density below that of non-planted MFC (max 0.83 vs 1 mW/m²), likely due to excessive root exudates and oxygen transfer interfering with cathode potential.
Was heißt das. If power generation is a priority, minimize plant root density or use slower-growing species; if nitrogen removal is the goal, accept the power trade-off for improved nitrification via plant-mediated aeration.
Ansatzpunkte6
Konkrete Lücken in dieser Publikation, jeweils mit einem Experiment, das sie schließen würde.
Hoch No measurement of N₂O or NO₂⁻ accumulation across the C/N range (2.67–8). Incomplete denitrification to N₂ could mask true nitrogen removal and reveal incomplete reduction pathways.
Paper reports NO₃⁻-N removal but not speciation of end products; at low C/N or high current, cathode potential may favor NO₂⁻ accumulation or N₂O slip rather than complete reduction to N₂.
Versuch. Gas chromatography or ion chromatography for N₂O, NO₂⁻, and NO₃⁻ at C/N 2.67, 4, 5.33, 6.67, 8 to map the denitrification pathway and identify optimal potential window.
Hoch No direct measurement of cathode and anode potentials (vs. Ag/AgCl or SHE). Only external voltage and internal resistance reported; electrode potentials are unknown.
Cathode potential controls denitrification selectivity and N₂O formation; anode potential affects organic oxidation efficiency. Paper states external resistance was 1000 Ω but does not report actual electrode potentials, limiting mechanistic understanding.
Versuch. Potentiostat-controlled experiments at fixed cathode potentials (e.g., −0.2, −0.4, −0.6 V vs. Ag/AgCl) across C/N range to map NO₃⁻ reduction, NO₂⁻ accumulation, and N₂O production.
Mittel Hydraulic retention time (HRT) fixed at 2 days; no variation tested. Unclear whether nitrogen removal is limited by contact time or by carbon/electron availability.
At low C/N, longer HRT might allow more complete denitrification; at high C/N, shorter HRT might reduce cost. Paper does not explore this trade-off.
Versuch. Test HRT 1, 2, 4 days at C/N 2.67 and 5.33 to determine whether nitrogen removal is kinetically or thermodynamically limited.
Mittel Dissolved oxygen (DO) in cathode region reported as 1.5–2.5 mg/L but not correlated with nitrification rate or ammonia removal. Unclear whether this DO level is optimal or limiting.
Nitrification requires DO; excess DO may suppress denitrification. Paper mentions DO range but does not test its effect on nitrogen speciation or removal kinetics.
Versuch. Vary plant density or aeration to control cathode DO (0.5–5 mg/L) and measure NH₄⁺-N oxidation rate and NO₃⁻ production to find optimal DO window.
Mittel Catholyte pH not reported. Denitrification kinetics and N₂O formation are pH-sensitive; pH drift could explain power and removal variations.
Paper measures influent/effluent water quality but does not report pH or pH gradient across the system. Cathode pH can drift due to proton consumption during denitrification.
Versuch. Monitor pH in anode, cathode, and bulk liquid across C/N range; test pH control (e.g., buffer addition) to isolate pH effects on nitrogen removal and power output.
Niedrig No comparison of HDPE filler performance against other high-surface-area materials (e.g., activated carbon, biochar, ceramic). SEM shows biofilm growth but not quantified.
Paper claims HDPE (500 m²/m³) is superior to gravel but does not benchmark against other fillers or quantify biofilm thickness/density.
Versuch. Parallel reactors with HDPE, activated carbon, biochar, and ceramic at C/N 4 and 8; measure biofilm biomass (MLVSS) and compare nitrogen removal and power output.
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Was gemacht wurde
- Systemtyp
- MFC
Was funktioniert hat
Zusammenfassung
The tail wastewater from sewage treatment facilities usually lacks carbon sources, and its subsequent treatment for deep nitrogen removal is difficult in natural conditions. In this study, the constructed wetland (CW) was integrated with microbial fuel cell (MFC) with high-density polyethylene (HDPE) fillers as the main matrix to improve nitrogen removal under inefficient carbon source conditions. Compared with the regular MFC and CW systems, MFC-CW attained higher nitrogen removal under low-carbon source conditions. The influence of influent carbon/nitrogen ratio (C/N) on the denitrification and electricity-generation performance was explored. Although the increase of carbon source simultaneously improved chemical oxygen demand (COD), ammonia (NH4+-N), nitrate (NO3−-N) and TN removal, the power generation during the carbon source adjustment showed low relation with the variation of influent COD in the range of 40–120 mg/L. CW was more dependent on carbon sources, and the addition of bioelectrochemical systems into MFC-CW could reduce the dependence of nitrogen removal on carbon sources, especially under low carbon source conditions. These findings offer valuable insights into the potential applications of MFC-CW for tail water treatment, and its parameters for utilization in real CWs should be explored in future studies.
Schlagwörter
Kennungen
- Zeitschrift
- Water
- Jahr
- 2023
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