Treatment of real wastewater from a paper mill with combined treatment of electrochemical oxidation and ultrasonic irradiation

Abstract

This study presents the effect of combined treatment of ultrasonic irradiation (UI) and electrochemical oxidation (EO) on real wastewater from a paper mill. Firstly, wastewater was treated with UI and EO separately and then it was treated with UI and EO together. Separate UI treatment of wastewater was able to achieve COD and color reduction by 40 % whereas the separate EO treatment was able to achieve COD and color reduction by 70–90 % (depending upon the combination of various parameters like current density, electrolyte concentration, pH, magnetic stirrer speed). However, when both processes were combined, they were able to achieve 100 % reduction of COD and color and that too in very less operation time (less than 80 min). Platinum coated titanium (Pt/Ti) sheet was used as anode and stainless steel sheet as cathode. Combined treatment was carried out at optimal conditions derived from separate EO treatment. These optimal conditions were 6 mA/cm2 current density, 1.5 gm/l NaCl concentration, 6 pH, and 400 rpm magnetic stirrer speed. UI not only provided an alternative way of creating turbulence but also helped in decomposing the pollutants by weakening their bonds. Moreover, it was found that energy consumption in combined UI and EO treatment is much less than the energy consumption in separate EO treatment with magnetic stirrer.