Simultaneous energy harvest and nitrogen removal using a supercapacitor microbial fuel cell

Area of Science:

• Environmental Engineering
• Electrochemistry
• Microbiology

Background:

• Microbial fuel cells (MFCs) face challenges in treating high-salinity wastewater due to limited pollutant removal and bioelectricity production.
• Existing MFC technologies struggle with efficiency when dealing with concentrated pollutants and saline environments.

Purpose of the Study:

• To develop and evaluate a novel supercapacitor MFC (SC-MFC) using carbon nanofibers composite electrodes for high-concentration saline wastewater treatment.
• To investigate the pollutant removal efficiency, power generation capabilities, and electrochemical properties of the SC-MFC using real landfill leachate.
• To analyze the mechanisms of extracellular electron transfer and nitrogen conversion within the bioanode.

Main Methods:

• Construction of a supercapacitor MFC (SC-MFC) with carbon nanofibers composite electrodes.
• Treatment of real landfill leachate at varying concentrations (10%, 20%, and 60%).
• Analysis of pollutant removal (COD, NH4+-N, TN), power output, electrochemical properties (impedance, current density), microbial community, and electron transfer pathways (DET, MET).

Main Results:

• The SC-MFC achieved higher removal rates for COD (59.4%), NH4+-N (78.2%), and TN (77.8%) with 60% leachate.
• Improved electrochemical performance was observed with 60% leachate, including lower internal resistance (Rt ≈ 6 Ω), higher exchange current density (i0 = 2.1 × 10⁻⁴ A cm⁻²), and larger catalytic current (j0 = 704 μA cm⁻²).
• A peak power output of 298 ± 22 mW m⁻² was achieved, with evidence of ammonium incorporation by chemoautotrophic bacteria and potential nitrogen conversion pathways. Direct electron transfer (DET) dominated extracellular electron transfer, and salt-tolerant denitrifying bacteria were identified as key microorganisms.

Conclusions:

• The SC-MFC demonstrates significant potential for efficient pollutant removal and energy harvesting from high-salinity wastewater, specifically landfill leachate.
• The study provides insights into the microbial and electrochemical mechanisms enabling effective treatment and power generation.
• This technology offers a promising avenue for sustainable wastewater management and resource recovery.