Alleviation of heat stress in electrostimulation assisted SBR treating thermophilic phenol wastewater: Performance, microbial community assembly, heat resistance mechanism and antibiotic resistance genes

An electrostimulation assisted sequencing batch reactor (ESBR) has excellent performance in improving phenol treatment performance and sludge characteristics under high temperature. The sludge volume index (SVI) and extracellular polymeric substances (EPS) content of ESBR were significantly reduced by 61.7% and 74.1% compared to SBR, respectively. The content of EPS was positively correlated with SVI, indicating that electrostimulation enhanced the settleability of sludge. Microbial community assembly under electrostimulation could be dominated by the deterministic process. The genes encoding heat shock proteins (Hsp15 and Hsp33) and synthesis genes encoding trehalose (TPS1 and otsA), and glycogen (GSY1) were up-regulated. The activation of the antioxidant system in ESBR inhibited the production of ROS, thereby hindering the transmission of ARGs under high temperature. The coexistence pattern of ARGs and genera indicated that the genus Ralstonia, Rhizobium, Schaalia, and Streptococcus were speculated to be the main hosts, thus electrostimulation reduced the abundance of ARGs hosts, thereby reducing the dissemination of ARGs under high temperature.