Integration of microalgae-microbial fuel cell (mMFC) with microbial electrolysis cell (MEC) for wastewater treatment and energy production

Microbial fuel cells based on microalgae (mMFCs) have attracted interest as long-term wastewater treatment plants (WWTPs). Through the metabolic activities of electro exogenic microorganisms, the mMFC incorporating these microorganisms can transform organic energy present in wastewater into electricity [1]. mMFCs can also sequester CO2 from the air and remove nitrogen pollutants from water. In this work, domestic wastewater was treated in the anodic compartment of a dual chamber mMFC. The anode and cathode were separated by a proton exchange membrane (PEM). Wetland treated water filled the cathodic compartment, and algal biomass was used as an effective catholyte. The influence of different working modes of micro algae based microbial fuel cells, such as batch and continuous mode, as well as different load implementations, on voltage was measured and analysed. To acquire the combined effect of voltage, two mMFCs in batch mode and one in continuous mode were linked in series. The overall voltage of 1.85V was used to run a 1-liter microbial electrolysis cell (MEC) operating at a temperature of 25^oC, pH range of 4.5 to 5.5, and a chemical oxygen demand COD of 10,000 mg/L. COD was eliminated with a 73 percent efficiency after treatment, and the hydrogen production rate was 9.8 ± 0.2 mL L^-1 d^-1. When compared to a continuous system, COD removal was found to be higher in Batch Mode. Both systems produced similar open circuit voltages. The continuous system had a higher columbic efficiency than the batch mode. The closed circuit voltage of a continuous system is higher than that of a batch system since it receives wastewater feed on a continual basis. The system may be scaled up to a pilot level of 1000 to 1200 L of working volume. A scaled-up system has the potential to generate significant amounts of bioelectricity, algal biomass, and biohydrogen.

References:

[1] Wastewater Treatment with Microbial Fuel Cells: A Design and Feasibility Study for Scale-up in Microbreweries. (2016). Journal Of Bioprocessing & Biotechniques. doi: 10.4172/2155-9821.1000267