Fenton-biological coupled biochemical oxidation of mixed wastewater for color and COD reduction

This study was focused to investigate the effectiveness of Fenton and photo-Fenton processes as a post-treatment technology for anaerobically pre-treated domestic, industrial, and combined (domestic + industrial) wastewater. Different dosage combinations of Fenton reagents (FeSO4/H2O2) were used to determine their optimum levels for the removal of color and chemical oxygen demand (COD). Optimum Fenton reagent combinations were found based on their color and COD removal efficiency given as: 10 mg FeSO4/L + 0.5 mL H2O2/L for domestic and combined wastewater, and 10 mg FeSO4/L + 1 mL H2O2/L for industrial wastewater. Photo-Fenton treatment (UV irradiation  30 min) showed the high color (> 90%) and COD (>80%) removal efficiency for all the three types of wastewater samples. Photo-Fenton process improved color removal up to 34% and COD reduction up to 40% compared to Fenton process. Statistical analysis showed that nature of wastewater did not affect the efficiency of photo-Fenton process. Thus, photo-Fenton treatment can be integrated with anaerobic process for the effective disposal of combined wastewater. This process integration may not only satisfy the national discharge limits of effluent, but it may be applied to the existing wastewater discharge settings in Pakistan.