Combined homogeneous and heterogeneous advanced oxidation process for the treatment of tannery wastewaters

This study investigated the practical application of combined advanced oxidation processes (AOPs), such as homogeneous TiO₂ photocatalysis and heterogeneous photo-Fenton, for the treatment of tannery wastewaters. An optimization study was conducted on the photocatalytic degradation of tannery wastewaters, in order to understand the effects of different operating parameters on the degradation kinetics. The chemical oxygen demand of tannery wastewater decreased from an initial level of 3,400 mg/L in raw wastewater to 140 mg/L (96% removal) in wastewater treated by the combined advanced oxidation process at optimum pH 7, TiO₂ dosage of 0.2 g/L, Fe²⁺ dosage of 0.5 g/L, H₂O₂ dosage of 1.8 g/L and a treatment time of 4 hours. The biodegradability of wastewater increased from an initial level of 0.4 to 0.7 after treatment under optimum experimental conditions at a treatment time of 60 min. An annual treatment cost of US$21.34/m³ of treated water was obtained. The combined advanced oxidation process proved to be an efficient and appropriate technique for the effective removal of complex organic compounds in industrial wastewater.