Enhanced bioremediation of toxic metals and harvesting electricity through sediment microbial fuel cell

Abstract

Performance of sediment microbial fuel cells (SMFCs) with aerated (A-SMFC) and nonaerated (NA-SMFC) cathodes was evaluated at different operating conditions in toxic metal removal and power generation. The A- and NA-SMFC open-circuit voltages were respectively about 665 and 275 mV, with quite steady performances for 120 days. The cell design points of both SMFCs were calculated by implementing polarization curves, and they were at 1 kΩ (power density 8.1 mW/m2 and current density 0.0504 mA/m2 with voltage 150 mV) for NA-SMFC and 100 Ω (power density 252.81 mW/m2 and current density 0.954 mA/m2 with voltage of 275 mV) for A-SMFC, respectively. Cathode potentials were at 30 kΩ 290 mV (NA-SMFC) and 500 mV (A-SMFC). As to the anode, at 30 KΩ, it was −180 mV (NA-SMFC) and 190 mV (A-SMFC). The voltammetry profiles of A-SMFC showed maximum current (forward scan, 22.7 μA; reverse scan, −19.4 μA) followed by NA-SMFC (forward scan, 11.3 μA; reverse scan, −9.5 μA). The cell design points of A-SMFC and NA-SMFC were altered after pH and temperature amendments at 200 and 700 Ω, respectively. As to metal removal rate, the maximum arsenic cadmium and lead removal was observed in A-SMFC at pH 7.0 (77.70%, 90.86%, and 83.91%) and 45°C (66.22%, 79.03%, and 71.17%). Scanning electron microscopy confirmed, at pH 7.0 and 45°C, an optimal biofilm growth at cathode and anode graphite of both SMFCs. After 120 days of operation, genomic DNA was extracted from biofilms and analyzed for rDNA 16S sequences. Similarity search was performed by using Basic Local Alignment Search Tool algorithm against the National Center for Biotechnology Information Gen Bank showing Pseudomonas spp. dominance at both anode and cathode. The results revealed that the A-SMFC system could be employed as an effective and long-term tool for power generation as well as stimulated bioremediation of the polluted sediments.