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

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 NO 3 − and NH 4 + as nitrogen sources. Finally, cultivation of the consortium under N 2 /CO 2 (70/30 %) atmosphere resulted in a significant enhancement in phenol and BTEX biodegradation. Under optimized conditions, the consortium C. vulgaris-R. opacus metabolized 100 % of a mixture of phenol, benzene, toluene, ethylbenzene 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 industries, which can be a low-cost and sustainable alternative for the biodegradation of petrochemical effluents. • C. vulgaris tolerates high concentrations of phenol and BTEX compounds. • The co-culture of R. opacus and microalgae improves pollutants biodegradation. • NH 4 addition to culture medium enhances the consortium microalga-bacterium. • Gaseous CO 2 supplementation improved biodegradation efficiencies. • Complete removal of BTEX and phenol at 3 mg L −1 under optimized conditions