The comparative process performance and efficiency of reactors treating swine wastewater for biogas production at 35 degrees C were evaluated for three biomass-retaining reactors with different configurations and operational conditions: an anaerobic sequencing batch reactor (ASBR), an upflow anaerobic sludge bed-filter (UBF) and an upflow solid reactor (USR). The maximum volumetric methane production rates of the ASBR, UBF and USR were 1.679,1.669 and 1.234 LL(-1)d(-1), respectively, at the OLR of 8 g TS L-1 d(-1). Compared with the USR, the ASBR and UBF achieved better performance, which was attributed to more efficient biomass retention indicated by a higher solids residence time-to-hydraulic residence time ratio. The worst performance of the USR was caused by serious washout of sludge. The microorganism distribution profile along with depth showed that methanogenic genera of Methanosaeta and Methanospirillum accounted for 81.37-90.83% and 77.67-88.50% of all archaeal clones in the ASBR and UBF, respectively, and presented non-obvious spatial heterogeneity, while the abundances of methanogenic genera decreased from 93.61 to 4.64% with depth in the USR, instead of an increase in the populations of acid resistant bacteria. (C) 2019 Elsevier Ltd. All rights reserved.