Role of a halothermophilic bacterial consortium for the biodegradation of PAHs and the treatment of petroleum wastewater at extreme conditions

Abstract

Petroleum hydrocarbons are major pollutants in marine environments. The present study describes the potential of a halothermophilic bacterial consortium capable of degrading polycyclic aromatic hydrocarbons (PAHs) in petroleum wastewater under extreme conditions. The consortium was enriched from brine originating from a desalination plant. The consortium efficiently degraded both the low molecular weight (LMW) PAHs-naphthalene (NAP), phenanthrene (PHN), anthracene (AN) and fluorene (FLU) as well as the high molecular weight (HMW) PAHs-pyrene (PY), benzo(e)pyrene (B(e)P) and benzo(k)fluoranthene (B(k)F), respectively. A nearly quantitative release of carbon dioxide (85 ± 1.2%) in conjunction with significant reduction of PAH concentration and an increase in bacterial cell count (from 104 to 109 cfu/mL) pointed at mineralization of PHN. The consortium was able degrade 86± 2.7% and 58± 4.1% of PHN (200 ppm) at 20% and 30% NaCl concentration respectively. Co-metabolism with PHN thereby enhanced the degradation of HMW PAHs. In petroleum refinery wastewater the PAHs were potently degraded by the bacterial consortium with 94 ± 3.8% COD removal in a continuous stirred tank reactor. Ochrobactrum halosaudia strain AJH1, Ochrobactrum halosaudia strain AJH2 and Pseudomonas aeruginosa strain AJH3 were present in the PAH-degrading halothermophilic consortium.