Desalter effluent is a difficult to treat wastewater stream emerging from petroleum refining operations. In this study, an osmotolerant and halotolerant yeast, Debaryomyces hansenii, was investigated for the first time for its use in removing phenol from simulated and actual desalter effluent. D. hansenii was able to degrade phenols at substrate COD concentrations ranging from 300-1200 mg L-1, whereas the substrate inhibition was noted as COD increased from 2000-4000 mg L-1. Three kinetic models (Andrews, Aiba, and Edward) were applied as unstructured mathematical models to simulate substrate inhibition kinetics with respect to phenol COD. Among all models, the Edward model best simulated the yeast growth on phenol. Using the Edward model, the model parameters were mu(max) 0.21 h(-1), K-S 633.95 mg center dot L-1, and K-I 1263.61 mg center dot L-1, respectively. The results in this study confirmed that D. hansenii has a high tolerance toward phenols and other organic compounds and salt found in desalter effluent. This yeast is therefore suggested to serve as an appropriate system from biological treatment of phenolic wastes in difficult to treat effluents such as desalter effluent.