Conventional biological wastewater treatments based on activated sludge system require substantial electric energy and produce excess sludge entailing further treatment. Therefore, an alternative, cost-effective wastewater treatment technology with efficient pollutant removal is essential. Microbial fuel cells (MFCs) have received much attention as a sustainable technology that can generate electricity simultaneously with wastewater treatment. MFC`s operation is based on the biocatalytic activity of electrochemically-active biofilm developed on the anode`s surface; therefore, an optimal nutrient ratio influent (C:N:P) is crucial for efficient wastewater treatment processes and a balanced microbial biofilm community structure. Previous studies, however, focused mainly on the engineering aspects of MFC reactors with little understanding of the microbiology involved. This research aimed to improve the understanding of MFC`s microbial ecology, specifically microbial key players in the reactor, under different C:N:P conditions, in order to increase MFCs performance. Since phosphate removal from wastewater is hardly examined in MFC systems, this study focused on the effect of different phosphate concentrations on MFC`s microbiology and performance using single-chamber air-cathode MFC reactors. Molecular characterization results showed a shift in community structure between the seed and the established community. Additionally, the planktonic community structure of the MFC bulk liquid was examined during kinetic measurements of acetate degradation. Surprisingly, a higher current could be attributed to planktonic cells rather than to the anodic electrochemically-active biofilm, implying that efficient soluble electron transfer mediators can exist under specific nutrient composition. Thus, there is a significant effect of wastewater chemical composition on microbial structure-function affecting electrochemical performance of MFC.
