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Bacterial communities, taxonomic functional groups, and chemical characteristics of granular sludge were assessed in an ultrahigh-temperature (70°C) upflow anaerobic sludge blanket reactor (UASB) used to treat super heavy oil-containing wastewater. The UASB, with an organic loading rate of 3.0 kg COD m−3 day−1, achieved an average chemical oxygen demand removal of 48%, with 52% oil removal from the wastewater. It was also found to successfully degrade two typical biomarkers of super heavy oil, C26-34 17α 25-norhopanes and C26-28 triaromatic steroid. Scanning electron microscope, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction results showed that the granular sludge became more compact with an increased quantity of extracellular polymeric substances, Fe2O3, FeS, and CaCO3 crystals in the reactor. Polymerase chain reaction-denaturing gradient gel electrophoresis and real-time polymerase chain reaction results indicated that after 90 days of operation, the density of total bacteria in the UASB dropped while Pseudomonas density increased, making it a dominant bacterium in the reactor. Data obtained from this research will provide useful information and insights with respect to effective treatment for super heavy oil wastewater under ultrahigh-temperature conditions. [ABSTRACT FROM AUTHOR]