Cloud point extraction procedure was used to remove hydrocarbons from aqueous streams coming from fuels storage centre. This real effluent was characterized by a high chemical oxygen demand (COD = 7000 mg O-2/L) clue to significant concentration of hydrocarbons as gasoline diesel and kerosene. Two biodegradable non-ionic surfactants (Lutensol AO7 and Triton X-114) were employed to treat this effluent. First, the phase diagrams of the binary systems, water-surfactant and the pseudo-binary system, water-surfactant-hydrocarbons were determined. The effect of sodium sulphate on water-surfactant-hydrocarbons systems was studied. The experimental results, with respect to surfactant wt.% and temperature, were expressed in term of residual (soluble) chemical oxygen demand (CODs), residual concentrations of surfactant in the dilute phase (X-t,X-w) converted to chemical oxygen demand (CODTA) and the volume fraction of coacervate (phi(C)) at the equilibrium. The results obtained for each parameter were represented on three-dimensional diagrams using an empirical fitting method. For instance, COD can be decreased from 7000 mg O-2/L to 50 mg O-2/L and 30 mg O-2/L. using Triton X-114 and Lutensol AO7, respectively at room temperature. However, the extraction extent of such effluent was found to be low at basic pH, which may be useful for surfactant regeneration. (C) 2010 Elsevier B.V. All rights reserved.