Bacterial and Granular Sludge Characteristics in an Ultrahigh-Temperature Upflow Anaerobic Sludge Blanket Reactor Treating Super Heavy Oil-Containing Wastewater

Abstract

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.