Evaluation of a novel electrochemical pilot plant process for azodyes removal from textile wastewater

A novel pilot plant for the electrochemical treatment of textile wastewater is discussed in this paper. The process is based on the electrolytic degradation of azodyes, applying a specific potential with on line measurement of current, pH and temperature. Batch experiments are performed for single electrolytic cell and continuous flow experiments for serial electrolytic cell apparatus (cascade system), using both synthetic and real wastewater samples. For synthetic samples treatment, four commercially pure azodyes (Reactive Orange 91, Reactive Red 184, Reactive Blue 182 and Reactive Black 5) are used, while sodium chloride (NaCl) and sodium sulfate (Na2SO4) are tested as supporting electrolytes. Real wastewater treatment under optimal conditions yield 94.4% dye removal and neutral final pH. Biologically Oxygen Demand measured after 5 days (BOD5) and Chemically Oxygen Demand (COD) values are reduced by 35 and 45%, respectively, while COD/BOD5 ratio is reduced from 4.3 to 3.6 final value. The proposed pilot plant achieves almost complete decoloration requiring no further addition of electrolyte or any other chemical agent. Thus, it could easily be used as a pretreatment stage prior to biological treatment.