Biodegradation of phenol in batch and continuous flow microbial fuel cells with rod and granular graphite electrodes

<p>Phenol biodegradation was evaluated in batch and continuous flow microbial fuel cells (MFCs). In batch-operated MFCs, biodegradation of 100–1000 mg L⁻¹ phenol was four to six times faster when graphite granules were used instead of rods (3.5–4.8 mg L⁻¹ h⁻¹ vs 0.5–0.9 mg L⁻¹ h⁻¹). Similarly maximum phenol biodegradation rates in continuous MFCs with granular and single-rod electrodes were 11.5 and 0.8 mg L⁻¹ h⁻¹, respectively. This superior performance was also evident in terms of electrochemical outputs, whereby continuous flow MFCs with granular graphite electrodes achieved maximum current and power densities (3444.4 mA m⁻³ and 777.8 mW m⁻³) that were markedly higher than those with single-rod electrodes (37.3 mA m⁻³ and 0.8 mW m⁻³). Addition of neutral red enhanced the electrochemical outputs to 5714.3 mA m⁻³ and 1428.6 mW m⁻³. Using the data generated in the continuous flow MFC, biokinetic parameters including <i>μ</i>_m, <i>K</i>_S, <i>Y</i> and <i>K</i>_e were determined as 0.03 h⁻¹, 24.2 mg L⁻¹, 0.25 mg cell (mg phenol)⁻¹ and 3.7 × 10⁻⁴ h⁻¹, respectively. Access to detailed kinetic information generated in MFC environmental conditions is critical in the design, operation and control of large-scale treatment systems utilizing MFC technology.</p