Oil field wastewater treatment in Biological Aerated Filter by immobilized microorganisms

As an alternative to the conventional activated sludge (CAS) process, this paper investigates the use of B350M and B350 group microorganisms immobilized on carriers in a pair of Biological Aerated Filter (BAF) reactors to pre-treat oil field wastewater before desalination. By operating the biodegradation system for 142 days with a hydraulic retention time (HRT) of 4 h and volumetric load 1.07 kg COD (m3 d)−1 at last, the reactor immobilized with B350M achieved mean degradation efficiencies of 78% for total organic carbon (TOC) and 94% for oil, whereas that with B350 only reached 64% for TOC and 86% for oil. The influent wastewater contains organic substances from C13H28 to C32H66, and a total of 16 polycyclic aromatic hydrocarbons (PAHs). The degradation efficiencies of PAHs in the BAF immobilized with B350M and B350 microorganisms are 90% and 84%, respectively. It is observed that the biological diversity of microorganisms in the reactor containing B350M (seven more strains of bacteria survive) is richer than in that containing B350. A large quantity of filamentous microorganisms developed in both reactors without causing foaming or bulking.