Biological treatment of organic compounds in produced water with use of halotolerant bacteria

Oilfield produced water (PW) is a mixture of different organic and inorganic compounds. The effects of discharging PW into the environment have lately become a major issue of environmental concern. This study aims to consider the capability of a gram-positive bacterium named Rhodococcus erythropolis PTCC 1767 in biological treatment of synthetic and real PWs. A stepwise adaptation strategy was applied for acclimation of the microorganism, by increasing chemical oxygen demand (COD) of the synthetic PW. The maximum COD removal efficiency was observed at 97% in PW with 600 mg/L COD. Also, by raising concentration of NaCl (up to 60 g/L), the stepwise adaptation strategy was performed for acclimated bacteria. The maximum COD removal efficiency occurred in the presence of 25 g/L NaCl. The results of total organic carbon (TOC) analysis revealed a removal efficiency of 85% and GC-MS analysis indicated a removal of 93% hydrocarbons (C-14-C-26). The adapted cells were then applied for treating the real PW in which a COD removal efficiency of 52% was achieved.