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 μm, KS, Y and Ke 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.
Keywords: Renewable energy; continuous flow microbial fuel cell; granular graphite; kinetics; phenol biodegradation.