Using microalgae for remediation of crude petroleum oil–water emulsions

Crude petroleum oil spills are among the most important organic contaminations. While the separated oils accumulated on the surface water are relatively easily removed, the emulsified portions are more difficult to remove and pose significant threats to the environment. Bioremediation using bacteria has proven to be an effective method, but the biomass produced in this case does not have any significant remunerative value. In this work, microalgae were proposed to combine emulsified oil remediation process with the potential of microalgae as a biofuel feedstock, thus enhancing the economic and environmental benefits of the process. A freshwater strain of Chlorella vulgaris was grown in water containing different concentrations of emulsified crude oil at different temperatures. The specific growth rate (μ_max) of the microalgae for each initial oil concentration was determined and was found to increase with the increase in initial oil concentration. For example, at 30°C, the specific growth rate, μ increased from 0.477 to 0.784 per day as the oil concentration increased from 57 to 222 mg/L. At 30°C, the effect of substrate concentration agreed with that of the microalgae growth, whereas at 40°C, the drop in oil concentration decreased with the increase in concentration. The results were fitted to a modified Monod kinetics model that used specific interfacial area as the influential substrate instead of the actual concentration. The results of this study clearly show the potential of using microalgae for emulsified oil remediation at relatively high concentrations.