Greenhouse Gas Control, Biofuel Recovery, and Nutrients Removal in Single-Chamber Microalgal Biocathode Microbial Fuel Cells

Abstract

In view of the current bottlenecks of low nitrogen and phosphorus removal efficiency and high cathode cost of microbial fuel cells (MFCs), this study constructed single-chamber biocathode MFCs to carry out related research. Single-chamber MFCs with microalgae were fabricated, and nitrogen removal efficiency and greenhouse gas emissions (GHG) were investigated. The results indicated that algae MFCs could significantly reduce GHG (CH4, CO2, and N2O) emissions through the competition of electron donor and sequestrating atmospheric CO2. Compared with the control group, the microalgal MFC significantly promoted the removal of total nitrogen (TN) and total phosphorus (TP). The highest open-circuit voltage (0.33 V) and power density (49 mW m−3) were observed in the closed circuit with algae (CC) reactor. Running MFC significantly increased the biomass of algae and produced good quality of biofuel. Quantitative polymerase chain reaction (q-PCR) analysis indicated that mcrA gene copies in the CC reactor (3.2×103 copies mL−1) were significantly higher than those of the no algae (NA) and CC reactors, while the lowest denitrifying gene copies (narG, nirS, and nosZ) were observed in the NA reactor. The Chloroflexi (22%) and Proteobacteria (31%) were the predominant bacterial communities in the CC reactor. Geobacter and Desulfobulbus were the main genera of exoelectrogens. This study can provide reference for nutrients (nitrogen, phosphorus) removal and GHG control in MFC wastewater treatment, but its long-term stability needs to be further studied.