Study on kinetics of co-metabolic degradation of para-nitrophenol and phenol using microbial fuel cell.

The experimental results of the present study show that phenol had a certain inhibitory effect on its utilization by phenol-acclimatized activated sludge (PAAS), which was the inoculum for the microbial fuel cell (MFC) inoculation. In co-metabolic study, utilization of para-nitrophenol (PNP) at low concentrations (< 20 mg L−1) when used with phenol at a fixed concentration (250 mg L−1) favorably proceeded. The behavior was interpreted in terms of carbon catabolite repression (CCR), indicating phenol (250 mg L−1) positively affected consumption of PNP (< 20 mg L−1). The calculated values of degradation rate show the necessity of phenol presence in the system where phenol acted on the inoculum's ability to withstand the inhibitory effect of PNP. The MFC functionality in electricity generation is also definable by considering CCR applicability and the results show that the negative effect of PNP was repressed by the presence of phenol. For instance, 20 mg L−1 PNP + 250 mg L−1 phenol yielded the highest power density (66.2 mW m−2) and the lowest internal resistance (189 Ω). The PAAS performance was characterized to evaluate cells' capacity in utilizing inhibitory substrates, and several different models were used. The relevant kinetic parameters are described in terms of PAAS affinity toward the substrate (ks) and the microbe's sensitivity in responding to the toxic substrate (ki). Luong and Aiba equations were chosen to describe MFC behavior when the PAAS utilized phenol as the sole substrate. While Haldane model was more capable of addressing co-metabolic degradation of PNP. [ABSTRACT FROM AUTHOR]