Treatment of a biodiesel effluent by coupling coagulation-flocculation, membrane filtration and Fenton reactions

The conditions for treatment of a biodiesel effluent, combining coagulation-flocculation and membrane filtration with Fenton/photo-Fenton reactions, in order to ensure the reuse of water, are presented in this work. Coagulation-flocculation and membrane filtration were applied as a first stage to remove the turbidity, suspended solids, apparent color and oil & fats. In the second stage, Fenton/photo-Fenton reactions were used to reduce the organic load. Under the best condition achieved for this stage (3500 mg L−1 H2O2, 25 mg L−1 Fe2+ and pH between 2.5 and 2.9), 90% of the dissolved organic carbon and the same percentage of chemical oxygen demand were removed after 24 of irradiation. In addition, the same acute ecotoxicity to Vibrio fischeri was obtained, when compared to the effluent treated in the first stage and diluted to 20% v/v. These results demonstrate the effectiveness of coupling physical processes with photo-Fenton reactions to promote the treatment of biodiesel effluent.