Phytoremediation of azo dye containing wastewater by using up-flow constructed wetlands

Abstract

Phytoremediation of a xenobiotic, like a textile azo-dye, acid orange 7 (AO7) in a pilot constructed wetland (CW), is feasible even for very high concentrations ([AO7] = 96.61 ± 3.57 mg/l). Removal efficiencies of approximately 99.03 %; 91.33% and 86.17% were obtained for AO7, COD and Ammonical Nitrogen (AN), respectively. Combination of aerobic and anaerobic processes in constructed wetlands can enhance the treatment performance in textile wastewater. This study assessed the treatment of azo dye Acid Orange 7 (AO7) a using three laboratory-scale up-flow constructed wetlands (UFCW) with and without supplementary aeration. Supplementary aeration controlled the size of aerobic and anaerobic zones in the UFCW reactors as evidenced by the oxidation–reduction potential (ORP) and dissolved oxygen (DO) profile of the UFCW. The AO7 removal efficiency was above 90% in all UFCW reactors and most of the color was extensively removed in the anaerobic region of the UFCW beds. The intermediates produced through the breakage of azo bond were significantly reduced in the UFCW reactors with supplementary aeration.