Introducing electrolysis to enhance anaerobic digestion resistance to acidification.

ABSTRACT

The phenomenon that the anaerobic system is inhibited by acid has always been a bottleneck hindering the application of anaerobic digestion (AD) technology. We tried to introduce electrolysis into AD to improve the acidification resistance, and eventually the productivity of the energy. In a batch fermentation device, the ability of electrochemical anaerobic digestion (EAD) to resist acidification was evaluated in current intensity, electrode potential, AC impedance, microbial community, pH value, and volatile fatty acids (VFAs). The results showed that the average concentration of VFAs in EAD was 32.9% lower than that in AD, the energy efficiency of EAD is 53.25% higher than AD, indicating that EAD has stronger anti-acidification ability and energy conversion efficiency than AD. When the EAD reaches a steady state, the current intensity fluctuates in the range of 7-12 mA, the electrode potential difference is maintained at 600 ± 5 mV, and the internal resistance decreases from 3333.3 ± 16Ω at startup to 68.9 ± 1.4Ω at the steady state, indicating that the EAD has stronger resistance to acidification may be due to the degradation of some VFAs on the electrode surface. Furthermore, the 16S rRNA sequencing analysis showed that the dominant electricity-producing bacteria on EAD anode surface were Clostridium, Hydrogenophaga and Trichloromonas, with a relative abundance of 40.32%, while the relative abundance of electrogenic bacteria in AD bulk solution and EAD bulk solution were about 1/2 and 1/4 that of EAD anode film, suggesting that the electricity-producing bacteria on the electrode surface play an important role in the degradation of VFAs.