The application of a combined electrochemical/membrane filtration process for treatment of wastewaters containing persistent pollutants was investigated. Phenol and an azo dye (Acid Orange 7, AO7) were used as model pollutants. A boron doped diamond electrode, the state-of-the-art in electrode material, was used as anode in the electrochemical treatment, following previous excellent results obtained with this kind of electrodes in the removal of soluble organic compounds from aqueous solutions. Reverse osmosis and nanofiltration membranes were used in the concentration step of a two-stage combined process.
The experimental conditions were selected in order to test the applicability of a model developed here, which predicts the chemical oxygen demand (COD) removal in the electrochemical treatment. The model was applied to estimate the COD evolution in the electrochemical reactor along a certain number of cycles of combined electrochemical/membrane filtration treatment using experimental data of observed rejections of the pollutants.
In terms of the overall efficiency of the treatment, the results show that very high COD removal values can be obtained in both the cases of phenol and AO7, above 95%, when comparing the COD of the membrane permeates which constitute the treated effluent, with the feeding solutions. © 2010 American Institute of Chemical Engineers Environ Prog, 2011.