Spatial distribution of biofilm conductivity in a Geobacter enriched anodic biofilm

Abstract

This study assessed the spatial distribution of biofilm conductivity (Kbio) across a multi-centimetre long anodic biofilm grown on an eight-electrode anode array at different growth conditions. A strong correlation was found between the spatial distribution of Kbio and the anodic biofilm thickness (Lf). The Kbio for different electrode pairs ranged between 0.6 and 0.7 mS/cm for Lf of 17–22 µm and increased to 1.15–1.64 mS/cm upon Lf growth to 38–53 µm. This increase in Kbio was accompanied by increase in current density from 1.15 ± 0.12 A/m2 to 2.1 ± 0.02 A/m2. Low half saturation potential was consistently found for electrode pairs having high values of Kbio and Lf. Microbial community revealed the dominance of Geobacter (>85%) on all electrode pairs. Acetate concentration significantly influenced the spatial distribution of Kbio. Long-term acetate starvation (3 days) resulted in up to 83% drop in Kbio along with decrease in current density to marginal values (<0.3 A/m2). However, the Kbio and current density rapidly recovered on restoring the acetate feed.