Sequential anaerobic-aerobic treatment of rice mill wastewater and simultaneous power generation in microbial fuel...

Microbial fuel cells (MFCs) have attracted widespread interest due to their capability to generate power while treating wastewater. In the present investigation, rice mill wastewater (RMW) was treated in a dual-chamber MFC with a biological cathode (MFC_B), in which anaerobic treatment was provided in the anode compartment, and aerobic treatment was enployed in the cathode compartment. The performance was compared with an identical MFC with an abiotic cathode (MFC_A). During continuous operation, the hydraulic retention time (HRT) of the anode compartments of both MFCs was kept at 12 h. The maximum volumetric power density obtained in MFC_B (379.53 mW/m³) was lower than MFC_A (791.72 mW/m³). Similarly, the maximum open-circuit voltage (OCV) and operating voltages were 0.519 V and 0.170 V for MFC_B, while for the MFC_A, they were 0.774 V and 0.251 V, respectively. The internal resistance of MFC_A was 372.34 Ω while the MFC_B showed a higher internal resistance of 533.89 Ω. The linear sweep voltammetry and cyclic voltammetry also demonstrated high electrochemical activity in MFC_A compared to MFC_B. However, MFC_B has shown a higher chemical oxygen demand (COD) removal efficiency (96.8%) than MFC_A (88.4%) under steady-state conditions. Both anaerobic and aerobic degradation of organic substrates significantly reduced the COD of RMW. Furthermore, the absence of an expensive catalyst in the cathode substantially reduces the cost of the system. The electrical performance of the system can be enhanced by employing novel cathode material with surface modification.