Pulp mill wastewater management using an advanced oxidation process and activated sludge

In this study, the electro-Fenton process (with response surface methodology as an experiments design and optimisation technique) was applied to evaluate the effects of five independent variables on the chemical oxygen demand (COD) and colour removal from paper pulp wastewater (PW). The parameters were statistically optimised under response surface methodology. The optimum conditions for 98.2% of COD and 96.8% of colour removal experimentally were at a reaction time of 30 min, current density of 79.9 mA/cm(2), pH of 6.9, hydrogen peroxide (H2O2)/PW volume ratio of 1.7 ml/l, hydrogen peroxide (H2O2)/ferrous ions (Fe2+) molar ratio of 1.6, electrode consumption of 0.1 (g/l) and energy consumption of 1.3 (kWh/m(3)). In the next step, the filtration process was carried out on the treated effluent obtained at the optimal conditions. Then, this was mixed with activated sludge in a ratio of 1 : 10; 99.9% of COD and colour removal was found after 150 and 60 min, respectively.