[Influence of substrate COD on methane production in single-chambered microbial electrolysis cell]

Area of Science:

• Environmental Science
• Biotechnology
• Electrochemistry

Background:

• Microbial electrolysis cells (MECs) utilize microbial biofilms for wastewater treatment and energy recovery.
• The chemical oxygen demand (COD) of the substrate significantly influences microbial activity in MECs.
• Understanding COD's impact is crucial for optimizing MEC performance.

Purpose of the Study:

• To investigate the effect of varying initial COD concentrations on the performance of a single-chamber methanogenic MEC.
• To examine methane production rate, COD removal, and energy efficiency under different applied voltages.
• To determine optimal conditions for energy recovery from low-strength wastewater.

Main Methods:

• A single-chamber MEC with a biocathode was constructed.
• Experiments were conducted with initial COD concentrations of 700, 1000, and 1350 mg/L.
• Applied voltages ranged from 0.3 to 0.7 V, and key performance metrics were measured.

Main Results:

• Methane production rate and COD removal increased with higher COD concentrations.
• Methane production and COD removal showed complex responses to applied voltage, peaking at 0.5 V for higher COD levels.
• The cathode potential reached -0.694 V at 0.5 V, promoting methanogenic bacteria growth and improving efficiency.
• Maximum energy recovery of 0.44 kJ was achieved at 1000 mg/L COD and 0.5 V.

Conclusions:

• Methanogenic MECs can achieve positive energy production from low-organic-concentration wastewaters.
• Optimizing COD concentration and applied voltage is key to maximizing energy recovery.
• This technology offers a promising method for energy recovery from domestic wastewater.