Integrating electrochemically-assisted anaerobic reactors with conductive media for enhanced methanation of greywater

Abstract

The utilization of bioelectrochemical systems is critical for the generation of methane via anaerobic digestion, and the process is influenced by the applied potential. The trajectory of biogas generation in five batch reactors showed important implications for methane production by synergistic effects of electric fields and conductive media allowing for attached growth of microorganisms. Synthetic greywater which is effective water source converts into methane within 5 days of reactor operation. The experiments emphasized that substrate availability enhanced the attached growth of microorganism in anaerobic settings. Reactor R2, with no microorganismgrowing surface, produced only 20 % of the methane produced by reactor R3, which contained Polyvinylidene fluoride (PVDF) media. The presence of current (0.5 V) increased CH4 by 1.35 times in case of nonconductive media (R3) and 1.6 times in conductive media higher than without external voltage. The study indicated a direct correlation between applied voltage and methane generation up to 1.0 V. The ratio of CO2/CH4 changed from 1.16 at 0 V (R1) to 0.362, 0.32, 0.267 and 0.296 for R2-R5 at 1.0 V, respectively. Regardless of surface conductivity, the presence of media for attached microbial growth was favorable for the slow growing methanogens. However, high throughput RNA sequencing showed that electrotrophic methanogens were more abundant with conductive media than non-conductive media under electric fields.