Electricity generation and treatment of paper recycling wastewater using a microbial fuel cell

Increased interest in sustainable agriculture and bio-based industries requires that we find more energy-efficient methods for treating cellulose-containing wastewaters. We examined the effectiveness of simultaneous electricity production and treatment of a paper recycling plant wastewater using microbial fuel cells. Treatment efficiency was limited by wastewater conductivity. When a 50 mM phosphate buffer solution (PBS, 5.9 mS/cm) was added to the wastewater, power densities reached 501 ± 20 mW/m², with a coulombic efficiency of 16 ± 2%. There was efficient removal of soluble organic matter, with 73 ± 1% removed based on soluble chemical oxygen demand (SCOD) and only slightly greater total removal (76 ± 4%) based on total COD (TCOD) over a 500-h batch cycle. Cellulose was nearly completely removed (96 ± 1%) during treatment. Further increasing the conductivity (100 mM PBS) increased power to 672 ± 27 mW/m². In contrast, only 144 ± 7 mW/m² was produced using an unamended wastewater (0.8 mS/cm) with TCOD, SCOD, and cellulose removals of 29 ± 1%, 51 ± 2%, and 16 ± 1% (350-h batch cycle). These results demonstrate limitations to treatment efficiencies with actual wastewaters caused by solution conductivity compared to laboratory experiments under more optimal conditions.