The role of conductive materials in the start-up period of thermophilic anaerobic system

Abstract

The major obstacle for thermophilic anaerobic digestion (TAD) is the inhibited microorganism activity and process instability during the start-up period. This study proposed a strategy to accelerate and stabilize the thermophilic reactors start-up via adding conductive materials. The results show that methane production rate in conductive materials supplemented (CMS) reactors was almost two times higher than the control reactors. Caloramator sp., a candidate of electroactive bacteria, was significantly enriched in the carbon nano-tube (CNT) supplemented groups (12.89%) as compared to control groups (1.26% only). Together with the doubled abundance of Methanosaeta and Methanosarcina methanogens in CMS groups, it is highly possible Caloramator sp. and Methanosaeta/Methanosarcina have established syntrophic direct interspecies electron transfer (DIET), via adopting conductive materials as electron conduit. Microbial community analysis indicates DIET was likely to be an unstable condition triggered syntrophic process. This study demonstrated that conductive materials could promote microbial activity and shorten start-up period for thermophilic anaerobic system.

Keywords: Conductive materials; Direct interspecies electron transfer; Exoelectrogen; Thermophilic anaerobic digestion.