In this study, a hazardous waste material of blast furnace dust (BFD) was applied in up-flow anaerobic sludge blanket (UASB) to enhance the anaerobic process. The response of COD removal efficiency and biogas production with BFD addition were higher than the blank group. The reduced redox potential optimized the type of fermentation by adding BFD, which could help converted volatile fatty acids (VFAs) into acetic acid for methanogenesis. With the sludge morphology and Fe speciation analysis, the iron ions became more stability to form a layer of hydroxides on the surface of the microorganism cells and the sludge became well-regulated, distinct and stable in RUASB-BFD. The distribution of microbial community revealed that the synergistic effects of Fe-C micro-electrolysis and magnetite increased the abundance of Firmicutes and Actinobacteria to degrade high molecular weight compounds, as well as methanogenesis pathway of acetoclastic and hydrogenotrophic promoting anaerobic digestion. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.