Enhancement of nitrate removal and electricity generation in microbial fuel cell using eggshell supported biocathode

[Display omitted] •MFC biocathode equipped with eggshell improved the nitrate removal in ground water.•Presence of eggshell facilitated the microbes to use nitrate as the TEA.•Eggshell improved the reduction kinetics which resulted in 97 % nitrate removal.•Microbial analysis identified the presence of denitrifying bacteria that involved in DIET mechanism. Microbial fuel cells (MFCs) are sustainable bio-electrochemical systems widely explored due to their ability of simultaneous electricity generation and wastewater treatment. However, the high cost and unfavorability due to untenable oxygen reduction reaction (ORR) kinetics upon utilization of platinum or other platinum derivative catalysts has led to the research on biocathodes as a suitable alternative. In the present research, the lower ORR and high cost is combated by biocathodes, where the microbes inherent in groundwater act as bio-catalysts enabling better ORR. Eggshell, a biowaste, is introduced into the catholyte and the MFC performance is monitored in terms of electricity production and nitrate removal. The ability of eggshell to bio-adsorb the nitrate prompting microbial growth improved the reduction kinetics at the cathode thereby enhancing MFC performance after three weeks of operation to result in a maximum power density of 228 ± 1.3 mW m−2 and 97 % nitrate removal. Microbial consortia analysis showed the maximum prevalence of denitrifying bacteria with the abundance of Pseudomonas, Azoarcus, Thauera, Wolinella, involved in reduction thereby attributing better characteristics for efficient performance. The present research thus, provides insights on the utilization of biocathodes and eggshell for simultaneous electricity generation and nitrate removal thereby provoking further investigations for upscaling MFC.