A simulation of acetate consumption and electricity generation in a single microbial fuel cell considering the diversity of nonelectrogenic bacteria

Abstract

To simulate acetate consumption and electricity generation in a cycle of a microbial fuel cell (MFC) treating synthetic acetate-based wastewater with low concentration, nonelectrogenic bacteria (NEB), which had no contribution in electricity generation, was incorporated with methanogen's kinetic parameters into a previous biofilm model proposed by Marcus et al. (Biotechnol Bioeng 98:1171-1182, 2007). However, the Coulombic efficiency was estimated to be 40.1%, whereas the experiment showed 13.6%, as the presence of NEB was obviously underestimated. Thus, the maximum NEB reaction rate (q_maxC) was temporarily calibrated, and a sensitivity analysis was then conducted. As a result, the growth parameters of NEB, the growth of the exoelectrogenic bacteria, and the biofilm detachment were identified as influential parameters. q_maxC and a half rate constant of NEB (K_sC) were selected as potential calibration parameters. The two sets of calibrated parameters (0.342 mmol-acetate (Ac)/mg-volatile solids (VS)/d of q_maxC and 33.8 mg-carbon (C)/L of K_sC; 0.274 mmol-Ac/mg-VS/d of q_maxC and 16.9 mg-C/L of K_sC) showed a good agreement with the experimental results at 100 mg-C/L of initial acetate. However, the calibrated parameter values obviously differed from those in previous models. The calibrated model also showed good agreement with the experimental results at 50 and 200 mg-C/L of the initial acetate. In view of the different values of q_maxC and K_sC from those of methanogenic bacteria in previous models and the previous findings on anode microbial community, which showed that NEB are not only methanogenic bacteria, we concluded that the diversity of NEB should be considered to simulate performances in a cycle of MFC treating low organic matter concentrations.

Keywords: Anode; Biofilm model; Kinetic parameter; Methanogenic bacteria; Microbial fuel cell.