Startup performance of microbial electrolysis cell assisted anaerobic digester (MEC-AD) with pre-acclimated activated carbon

Abstract

The feasibility of using pre-acclimated activated carbon to start up microbial electrolysis cell assisted anaerobic digester (MEC-AD) has been testified in this study. Two identical lab-scale digesters were separately packed with granular activated carbon (GAC) and powered activated carbon (PAC), which were initially acclimated as anaerobic digester and then transferred to MEC-AD. When a voltage of 0.5 V was applied, increased methane generation and substrate removal rates were observed. Hydrogenotrophic methanogens predominated in both digesters before and after transition, indicating that the pre-cultured microbial community on carbon materials could provide necessary microbiome favorable for starting up MECs. Although a low abundance of Geobacter was detected in inoculum, a rapid propagation could be realized when reactors were subjected to the electro-stimulation. The abundance of Methanosarcina closely attached to PAC was four times than that of GAC, which might be partially contributed to the improved resilience of anaerobic digester subjected to electro-stimulation.

Keywords: Activated carbon; Direct interspecies electron transfer; Geobacter; Hydrogenotrophic methanogens; Volatile fatty acids.

Fig. 1

Schematic diagram of the MEC-AD combined system.

Fig. 2

Variations of (a) pH and (b) TOC in effluent from R1 and R2.

Fig. 3

The VFAs variation of R1 (GAC) and R2 (PAC) during different stages.

Fig. 4

Variations of biogas generation during different stages: (a) volumetric gas yield, (b) biogas content from R1 and (c) biogas content from R2.

Fig. 5

Archaeal taxonomic distributions.

Fig. 6

(a) Bacterial community heatmap at genus level, (b) one-way ANOVA analysis.