Decontamination of tannery industry wastewater containing high organic load along with Cr3+: a comparative study

Abstract

ABSTRACTThe applicability of different advance oxidation processes (UV, H2O2/UV, Fe2+/H2O2/UV and Fe3+/H2O2/UV, Fe2+/H2O2) to treat real tannery wastewater was investigated in this work, and their efficiency was compared. Reduction of chemical oxygen demand (COD) and removal of chromium was envisaged through two consecutive processes: COD reduction followed by chromium removal. Comparisons of the specific energy consumption between UV, UV/H2O2 system, UV/H2O2/Fe2+, UV/H2O2/Fe3+ system were also reported. The chemical precipitation processes with different precipitating agents, CaO, MgO and NaOH, for the removal of chromium was investigated. Chromium removal and sludge volume at different pH values for three precipitating agents were assessed. The sludge generated during chemical precipitation has been characterized. The experimental results show that optimum conditions for Fe2+/H2O2 are 2 M H2O2, 0.04 M Fe2+, pH 3 and for Fe2+/H2O2/UV these are 0.5 M H2O2, 0.04 M Fe2+. The photo‐Fenton system with lower H2O2 dosage (0.5 M) and lower duration (60 min) could achieve same extent of COD reduction (97%) achieved in Fenton's treatment with higher (2 M) H2O2 dosage and longer duration (90 min) of treatment.The results demonstrated that the photo‐Fenton process was superior over other processes. The wastewater treated with CaO and MgO met the stringent discharge limit of below 1 mg/L for total chromium. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.