Bioelectrochemically assisting anaerobic digestion enhanced methane production under low-temperature

Abstract

Bioelectrochemical systems (BES) with carbon brush electrode were developed to improve methanogenic performance of low-temperature (15 °C) anaerobic digestion (AD) in this study. It turned out that the BES system (1.0 V) could significantly improve the CH4 yield, and during the reaction process, propionic acid (∼618.73 mg/L) had a serious accumulation. Metatranscriptomic analysis revealed that methane was mainly produced by acetoclastic methanogenic pathway, and application of voltage could promote its improvement. On carbon brush electrodes, the enhancement of the acetoclastic pathway mainly depended on acetate kinase (Pta) and phosphate acetyltransferase (Ack) to convert acetate to acetyl-CoA. While it was mainly regulated by the acetate-CoA ligase (Acs) in fluid activated sludge. The activity of methanogenesis-related enzymes on the cathode was generally higher than that on the anode, while the enzyme activity on the fluid sludge anode was mostly inhibited. In addition, BES system significantly increased the abundance of methanogens and electrogens, and enhanced the activity of electron transfer related enzymes, which greatly promoted the direct interspecies electron transfer (DIET) of species. Therefore, the BES system could be an attractive alternative strategy to improve the performance of AD when treating low-temperature wastewater.