Bioanodes/biocathodes formed at optimal potentials enhance subsequent pentachlorophenol degradation and power generation from microbial fuel cells

Bioanodes formed at an optimal potential of 200 mV vs. SHE and biocathodes developed at -300 mV vs. SHE in bioelectrochemical cells (BECs) enhanced the subsequent performances of microbial fuel cells (MFCs) compared to the un-treated controls. While the startup times were reduced to 320 h (bioanodes) and 420-440 h (biocathodes), PCP degradation rates were improved by 28.5% (bioanodes) and 21.5% (biocathodes), and power production by 41.7% (bioanodes) and 44% (biocathodes). Accordingly, there were less accumulated products of PCP de-chlorination in the biocathodes whereas PCP in the bioanodes was more efficiently de-chlorinated, resulting in the formation of a new product of 3,4,5-trichlorophenol (24.3 ± 2.2 μM at 96 h). Charges were diverted to more generation of electricity in the bioanodes at 200 mV while oxygen in the biocathodes at -300 mV acted as a primary electron acceptor. Dominant bacteria known as recalcitrant organic degraders and/or exoelectrogens/electrotrophs included Desulfovibrio carbinoliphilus and Dechlorospirillum sp. on the bioanodes at 200 mV, and Desulfovibrio marrakechensis, Comamonas testosteroni and Comamonas sp. on the biocathodes at -300 mV. These results demonstrated that an optimal potential was a feasible approach for developing both bioanodes and biocathodes for efficient PCP degradation and power generation from MFCs.