Effect of nickel (II) on the performance of anodic electroactive biofilms in bioelectrochemical systems.

The impact of nickel (Ni) on the performance of anodic electroactive biofilms (EABs) in the bioelectrochemical system (BES) was investigated in this study. Although it has been reported that Ni influences microorganisms in a number of ways, it is unknown how its presence in the anode of a BES affects extracellular electron transfer (EET) of EABs, microbial viability, and the bacterial community. Results revealed that the addition of Ni decreased power output from 673.24 ± 12.40 mW/m at 0 mg/L to 179.26 ± 9.05 mW/m at 80 mg/L. The metal and chemical oxygen demand removal efficiencies of the microbial fuel cells (MFCs) declined as Ni concentration increased, which could be attributed to decreased microbial viability as revealed by SEM and CLSM. FTIR analysis revealed the involvement of various microbial biofilm functional groups, including hydroxyl, amides, methyl, amine, and carboxyl, in the uptake of Ni. The presence of Ni on the anodic biofilms was confirmed by SEM-EDS and XPS analyses. CV demonstrated that the electron transfer performance of the anodic biofilms was negatively correlated with the various Ni concentrations. EIS showed that the internal resistance of the MFCs increased with increasing Ni concentration, resulting in a decrease in power output. High-throughput sequencing results revealed a decrease in Geobacter and an increase in Desulfovibrio in response to Ni concentrations of 10, 20, 40, and 80 mg/L. Furthermore, the various Ni concentrations decreased the expression of EET-related genes. The Ni-fed MFCs had a higher abundance of the nikR gene than the control group, which was important for Ni resistance. This work advances our understanding of Ni inhibition on EABs, as well as the concurrent removal of organic matter and Ni from wastewater.