Cost-effective domestic wastewater treatment and bioenergy recovery in an immobilized microalgal-based photoautotrophic microbial fuel cell (PMFC)

An immobilized microalgal-based photoautotrophic microbial fuel cell (PMFC) was developed for the first time as a cost-effective process for simultaneous nutrients removal and bioenergy recovery from domestic wastewater. The PMFC could achieve up to 93.2% of sCOD, 95.9% of NH4+-N, 95.1% of TN, and 82.7% of PO43--P removal efficiency, as well as 466.9 mW m(-3) of maximum power density. Organic matters were mainly removed in the anodic chamber, in which electricity generation, sulfate reduction, fermentation and methanogenesis might occur. Besides, assimilation of nutrients into microalgal biomass in the cathodic chamber was identified as the main sink of nitrogen (27.7-50.0%) and phosphorus (37.1-67.9%). It should be noted that the synergistic interactions among photosynthesis, nitrification, aerobic denitrification and autotrophic denitrification in the cathodic chamber played significant roles in efficient TN removal capability. In addition, a preliminary energy flow analysis indicated that electricity generation in the PMFC accounted for 12.7-42.3% of the energy consumption. A higher microalgal biomass growth rate (up to 375.7 mg L-1 d(-1)) favored the downstream biodiesel production process, and biodiesel in algal biomass could achieve energy neutrality theoretically and significantly enhanced the economic benefits of the PMFC. These results present the feasibility of the PMFC for simultaneous domestic wastewater treatment and bioenergy recovery in a cost-effective way.