Removal of Chemical Oxygen Demand and Color from Simulated Textile Wastewater Using a Combination of Chemical/Physicochemical Processes

Abstract

The treatment of simulated textile wastewater [chemical oxygen demand (COD) = 3360 mg/L] was performed using three chemical/physicochemical processes, viz., coagulation, Fenton oxidation, and adsorption. Coagulation of the wastewater was performed in a jar test apparatus using inorganic and organic coagulants. The best color removal (∼96%) was obtained with FeSO4 while FeCl3 and MgCl2 caused ∼75% and ∼53% color removal, respectively. The optimum dose for iron-based coagulants was 3 g/L, whereas it was 6 g/L for MgCl2. FeSO4-treated wastewater showed the best results with regard to the settling of flocs. Chitosan was effective for the decolorization of wastewater at low dose (=10 mg/L) and acidic pH (∼3.0) showing ∼20% and 30% COD and color reductions, respectively. For coagulation with FeSO4 followed by adsorption, overall COD and color removal of 85% and 99%, respectively, could be achieved. The raw wastewater treated by Fenton’s process (H2O2 dose = 10.5 g/L and H2O2/Fe2+ molar ratio = 20) exhibited COD and color removal of ∼80% and 99%, respectively. Using Fenton oxidation as a post-treatment step after coagulation with FeSO4, the COD removal was enhanced to ∼83%, although the color removal remained unaffected. The sequential treatment also increased the BOD5 (biochemical oxygen demand) to COD ratio of the treated wastewater to 0.51.