Offshore Produced Water Treatment by a Biofilm Reactor on the Seabed: The Effect of Temperature and Matrix Characteristics

Abstract

Produced water (PW) from offshore oil and gas operations is currently being discharged without treatment for dissolved pollutants due to space limitations. A biofilter on the seabed adjacent to a production platform would negate all size restrictions, thus reduce the environmental impact of oil and gas production offshore. Moving bed biofilm reactor (MBBR) treatment was investigated for PW with various high salinity from different oilfields in the North Sea at 10 °C and 40 °C, corresponding to the sea and PW temperature, respectively. In continuous operation over a year, MBBR achieved a stable COD removal of 64±5% at 10 °C and 68±8% at 40 °C. Batch experiments revealed that most dissolved compounds were removed within 3 hours of treatment alongside with toxicity for PW, including PW samples with high oil in water from unstable production. High temperature was a relevant parameter to achieve faster kinetics. MBBR thus seems a realistic solution to treat industrial wastewater with complex and variable composition by removing harmful components towards the zero harmful discharge goal.

Keywords: High salinity, temperature, biofilm, Biological treatment, offshore, industrial wastewater