A field pilot study has been constructed in the Liaohe oilfield, China to treat heavy oil wastewater with
large amounts of dissolved recalcitrant organic compounds and low nutrient of nitrogen and phosphorus
by an upflow anaerobic sludge blanket (UASB) coupled with immobilized biological aerated filters (IBAFs).
By operating the system for 252 days (including the start-up of 128 days), the chemical oxygen
demand (COD), ammonia nitrogen (NH3-N) and suspended solid (SS) in the wastewater were removed by
74%, 94% and 98%, respectively. GC–MS analysis indicated that most of alkanes were degraded by the UASB
process, while the I-BAF played important roles both in degrading organic compounds and in removing
the NH3-N and SS. The bacterial community structural analysis based on the PCR-DGGE technology reveals
that the predominant bacteria in the UASB reactor belong to the Bacillales and Rhodobacterales, and that in
the I-BAF was identified as uncultured soil bacterium. Our results suggest that the combined biotreatment
system has immense potential in large-scale treatment of heavy oil wastewater.