The applicability of combined physico-chemical processes for treatment and reuse of synthetic textile reverse osmosis concentrate

The purpose of this research aims to investigate the feasibility of combined processes by applying electrocoagulation (EC), electrofenton (EF) enhanced by electrodialysis (ED) for treating a synthetic textile reverse osmosis (RO) concentrate stream, using different concentrations of dyes (mixture of reactive red 70% and reactive orange 30%) and monovalent NaCl salt. Firstly, single degradation step was integrated using aluminum and iron electrodes respectively for EC and EF, to reduce COD and color, under operating parameters such as electrolysis time, current density, pH, interelectrode distance and peroxide dosage. Secondly, ED was applied for desalination step. Finally, cost analysis was made according to sludge removal, chemicals, electrodes and energy consumptions, for all systems. Hybrid EF/ED and EC/EF/ED were found as effective and economically feasible for treating RO concentrate, as they presented similar results and the best removal efficiencies (total decolorization, 98 and 99.2% COD, 92 and 94% salinity, respectively). As regards hybrid EC/ED, COD, color and salinity abatement rates did not overpass 58, 86 and 40%, respectively. Moreover, by implementing EF, operating cost (2.41 US$/m(3)) was slightly low comparing with EC (3.56 US$/m(3)), and therefore cost analysis proves EF was economically more efficient than EC. EF/ED process was suitable in reducing ED membrane fouling and improving deionization efficiency of the treated RO brine, which facilitates its direct discharge or reuse.