Enhanced anaerobic phenol degradation by conductive materials via EPS and microbial community alteration

Anaerobic biodegradation is a promising and economical process to remove phenol in the wastewater, although the reaction kinetics are often limited by the toxicity of phenol. This study proposed a strategy to accelerate phenol degradation and mitigate its inhibition on the bioprocess by adding conductive materials (CMs) into the anaerobic degradation system. The results showed that CMs could stimulate phenol degradation up to one–fold higher than that in control group. Certain extracellular polymeric substances (EPS) compounds that can act as electron shuttles, i.e. protein and humic substances, were greatly enriched with the existence of CMs. In particular, compared with control group, CMs supplemented groups had 2.3 and 10 to 20 folds low molecular weight protein in bound and soluble EPS, respectively. Carbon nanotube supplemented group exhibited 3 times higher humic substance in soluble EPS. The overall electron transport system activity in CMs groups was much higher than that in control groups. The addition of CMs enriched phenol degradation bacteria–Syntrophorhabdus, Brooklawnia, Treponema and Syntrophus, as well as electroactive methanogens–Methanosaeta. It is proposed that Syntrophus and Methanosaeta were the functional genera in methanogenic phenol degradation via extracellular electron transfer. This study revealed that the presence of CMs altered the EPS composition and microbial community of the system and made it become more favorable for extracellular electron transfer.