Treatment of pulp and paper industry bleaching effluent by electrocoagulant process

The experiments were carried out in an electrocoagulation reactor with aluminum as sacrificial electrodes. The influence of electrolysis time, current density, pH, NaCl concentration, rotational speed of the stirrer and electrode distance on reduction of color, COD and BOD were studied in detail. From the experimental results, 15 mA/cm2 current density, pH of 7, 1 g/l NaCl, 100 rpm, 28 °C temperature and 3 cm electrode distance were found to be optimum for maximum reduction of color, COD and BOD. The reduction of color, COD and BOD under the optimum condition were found to be 94%, 90% and 87% respectively. The electrode energy consumption was calculated and found to be varied from 10.1 to 12.9 kWh/m3 depending on the operating conditions. Under optimal operating condition such as 15 mA/cm2 current density, pH of 7, 1 g/l NaCl, 100 rpm, 28 °C temperature and 3 cm electrode distance, the operating cost was found to be 1.56 US $/m3. The experimental results proved that the electrocoagulation is a suitable method for treating bleaching plant effluents for reuse.