Innovative pilot-scale constructed wetland-microbial fuel cell system for enhanced wastewater treatment and bioelectricity production

In this study, a unique configuration of pilot scale constructed wetland-microbial fuel cell (CW-MFC) system was evaluated in terms of chemical oxygen demand (COD) removal from synthetic wastewater and bioelectricity generation. The system consists of nine individual CW-MFC units and two aerobic chambers configured in a fibre-reinforced rectangular tank (Total working volume-135.5 L). Typha angustifolia was used as wetland plant. To enhance electrical performance of the system, two auxiliary MFCs equipped with terracotta-based separator-electrode-assembly (SEA) were integrated into the anodic zone of each CW-MFC unit in addition to the conventional sediment-configured MFC. The system was evaluated in fed-batch and continuous up-flow modes of operations. All the CW integrated MFCs were studied individually without any combinations (parallel/series). In fed-batch mode, the CW-MFC unit of the system removed a maximum of 97.56 ± 1.6 % of COD from wastewater. The highest power and current densities achieved by the auxiliary MFCs were 58.55 mW/m2 and 229.6 mA/m2 respectively. In the continuous up-flow mode, the pilot-scale system treated around 4100 L of wastewater and exhibited a maximum of 82.8 ± 1.9 % COD removal efficiency. Whereas, the auxiliary MFCs attained the maximum power and current densities of 41.44 mW/m2 and 283.3 mA/m2 respectively. In both modes, the internal resistance of the auxiliary MFCs was found to be two times lower than that of the conventional sediment-configured MFCs of the system. The overall results manifested that the inclusion of SEAs and aerobic chambers in this innovative pilot-scale CW-MFC shows merit and improved the energetics of the system.