Treatment of real wastewater from the graphic industry using advanced oxidation technologies: Degradation models and feasibility analysis

Abstract

Many organic contaminants present in industrial effluents are resistant to conventional treatments. The application of Advanced Oxidation Technologies (AOT's) to a system of great complexity and unknown composition was studied. The proposed AOT's arise from the combination of UV light irradiation (254 nm) in the presence of commercial steel wool (CSW - zerovalent iron) and H2O2 as an oxidant, resulting in degradation processes by UV photolysis, UV/H2O2, Fe°/H2O2 and UV/H2O2/Fe°. The system used was an effluent from a graphic industry. High organic load and low biodegradability are characteristics of these wastewaters. The CSW was characterized by SEM/EDS. The effect of pH, H2O2 concentration, mass of CSW, intensity of UV light and temperature on the reduction of chemical oxygen demand (COD) of the effluent was evaluated employing a screening design. Afterwards, significant factors ([H2O2], light intensity and temperature) were selected to study their effect on COD reduction employing a central composite design. Optimum operating conditions predicted (0.06 mol L− 1 of H2O2, UV254 nm of 1.6 × 10− 5 E s− 1 and 44 °C at pH ca. 6.5.) generated an experimental COD reduction of 98.22% at lab scale. These conditions were also tested at pilot scale. Furthermore, phytotoxicity of treated effluents was analyzed.