Produced water treatment by membrane aerated biofilm reactors at elevated oxygen partial pressures

Produced water (PW) is a waste stream of crude oil extraction with high content of organic materials, metals and high salinity. Membrane aerated biofilm reactors (MABRs) can be a method to reduce the organic matter and toxicity of this streams prior to discharge in the sea. Given the limited space on offshore platforms, it is preferred to locate the reactor on the seafloor. This could result in energy savings due to more efficient oxygen mass transfer at high pressures. Treatment of PW by three MABRs operating with lumen pressures of 0.2, 0.6 and 1.0 bar oxygen was investigated at laboratory scale. Reactors were fed continuously at hydraulic retention times (HRTs) of 24, 12 and 6 hours. After adaptation, 24 h batch experiments were conducted to assess biokinetics. All reactors removed a large fraction (up to 55 – 75%) of the organic content. The initial toxicity was completely removed with 24 hours.