Electrical voltage application as a novel approach for facilitating methanogenic granulation

[Display omitted] •Electrical voltage (EV, 0.3 V) was applied for facilitating granulation in UASB.•EV could form big, settleable, and hydrophobic granules within 50 d.•EV also increased the specific methanogenic activity up to two times.•Pseudomonas and Methanosaeta relative abundances were 17 and 28% higher in EV.•Increased expression of quorum sensing genes by 27 times. Despite having high-rate methanogenic performance, up-flow anaerobic sludge blanket reactor still has challenges regarding long-start up period (3–8 months) for granulation. In this study, “electrical voltage (EV, 0.3 V) application” was attempted for facilitating granulation in the continuous operation with increased organic loading rates (0.5–11.0 kg COD/m3/d). Up to 11.0 kg COD/m3/d, EV-reactor exhibited the stable performance, while the control failed. After 49 days of operation (at 7 kg COD/m3/d), the granules collected from EV-reactor had larger diameter (2.3 vs 1.6 mm), higher settling velocity (2.6 vs 1.9 cm/s), and higher hydrophobicity (52.1 % vs 34.5 %), compared to the control. EV application also increased the specific methanogenic activity for propionate and hydrogen almost by two times. The relative abundance of Pseudomonas sp. (quorum sensing (QS)-related microbe) in EV-reactor was 17 % higher than that in the control. In addition, EV application increased the expression of QS genes significantly by 27 times.