Detecting Excess Biofilm Thickness in Microbial Electrolysis Cells by Real-Time In-Situ Biofilm Monitoring

Area of Science:

• Bioelectrochemical Systems (BES)
• Microbial Electrolysis Cells (MECs)
• Biofilm Engineering

Background:

• Stable operation of BES requires avoiding mass transfer limitations in electroactive biofilms.
• pH gradients and substrate limitations can reduce BES electrical performance.
• Biofilm morphology significantly impacts the efficiency of microbial electrolysis cells.

Purpose of the Study:

• To investigate the impact of mixed-species electroactive biofilm morphology on MEC electrical performance.
• To identify optimal biofilm characteristics for wastewater treatment applications.
• To establish a correlation between biofilm thickness and current density.

Main Methods:

• Noninvasive monitoring using optical coherence tomography.
• Real-time evaluation of biofilm morphology with an industrial biofilm sensor.
• Cultivation of mixed-species electroactive biofilms in MECs.

Main Results:

• Maximum current density of approximately 3.5 A/m² achieved with biofilms of 100-150 µm mean thickness.
• Thicker biofilms (>150 µm) led to mass transfer limitations and reduced efficiency.
• Biofilm detachment and declining efficiency necessitate active biofilm thickness control.

Conclusions:

• Biofilm thickness is a critical parameter for optimizing MEC performance.
• Active management of biofilm thickness is essential for sustained high efficiency in wastewater treatment.
• A mean biofilm thickness of 100-150 µm represents an optimal range for maximizing current density in MECs.