Treatment of oil-produced water using a fungus–microalga consortium

The consortium between microalga and fungus can be used in wastewater treatment due the combination of their metabolisms, but this application in petroleum-produced water has not been verified in the literature. This study investigated the microalga-fungus consortium for the treatment of oil-produced water by varying the initial TPH (total petroleum hydrocarbons) concentrations in the effluent between 312 and 2500 mg L −1 , the salinity between 5 and 50 g L −1 , and at different concentrations of nitrogen (25, 50, and 100 mg L −1 ) and phosphorus (approximately 30 mg L −1 ). A synthetic effluent (modified BG-11 medium) with crude oil as a carbon source was used. The microalga Tetradesmus obliquus LCE-01 and the filamentous fungi Aspergillus niger , Penicillium oxalicum , and Cunninghamella echinulata were the species chosen. The experiments were performed in an aerated bubble column reactor at a rate of 1.5 vvm, using illumination of 100 µmol m −2 s −1 (for microalgal experiments) and room temperature between 30 and 35 °C. By cultivating all fungi and microalga separately and in co-culture, it was found that the highest contribution to TPH removal was made by the filamentous fungi, with C. echinulata achieving removal efficiencies between 90 and 95%. With respect to salinity, it was observed that T. obliquus was able to survive up to concentrations of 25 g L −1 , and C. echinulata not only grew in all saline concentrations tested but also significantly removed TPH at rates between 80 and 95%. The co-cultivation of the fungus with the microalga removed higher percentages of nitrogen (as nitrate), of 63.4, 44.4, and 31.7%, considering initial concentrations of 25, 50, and 100 mg L –1 , respectively. A similar average of 36.58 ± 4.82% of phosphorus removal percentage was found for all experiments (initial phosphorus concentration of 30 mg L –1 ). When the real effluent was tested, TPH, nitrogen, and phosphorus were removed efficiently by the microalga–fungus consortium presenting higher efficiency than the monocultures. Graphical abstract