Developing a microalgal-bacterial consortium for the removal of organic pollutants from petrochemical industry

Abstract

Organic pollutants are one of the most hazardous contaminants due to their toxicity and ubiquity. The presence of organic compounds, such as phenol or BTEXs (benzene, toluene, ethylbenzene and xylene), in petrochemical wastewater causes severe damage in aquatic environments. Different bioremediation technologies have been tested, but with limited efficiencies. This work assessed the biodegradation potential of a consortium composed of the microalga Chlorella vulgaris and the bacterium Rhodococcus opacus at different levels of phenol and BTEXs in batch assays, which could be a first step to solve the limitations of previous technologies, especially at low concentrations of pollutants. The results showed that C. vulgaris tolerated and metabolized high concentrations of these contaminants: 100 mg L 1 of phenol, 15, 8, 3 and 1 mg L 1 of benzene, toluene, ethylbenzene and o-xylene, respectively. Moreover, the co-cultivation of R. opacus and C. vulgaris enhanced organic pollutant biodegradation when using NO3 and NH4 + as nitrogen sources. Finally, cultivation of the consortium under N2/CO2 (70/30 %) atmosphere resulted in a significant enhancement in phenol and BTEX biodegradation. Under optimized con- ditions, the consortium C. vulgaris-R. opacus metabolized 100 % of a mixture of phenol, benzene, toluene, eth- ylbenzene and o-xylene at 25, 3, 3, 3 and 1 mg L 1, respectively, within 6 days of cultivation. These results highlight the potential of algal-bacterial consortia to biodegrade organic pollutants from petrochemical in- dustries, which can be a low-cost and sustainable alternative for the biodegradation of petrochemical effluents.