Treatment of landfill leachate by electrocoagulation

Abstract

In recent times treatment of landfill leachate by nonconventional methods such as the electrochemical process has been increasing for its treatment efficiency. Among the electrochemical techniques, the process of electrocoagulation (EC) has largely been employed to remove heavy metals from municipal and industrial wastewaters. However, solid waste landfill leachate treatment with the aim of Chemical Oxygen Demand (COD) removal and Ammonia-Nitrogen (NH3-N) removal have not been studied so much using different types of electrodes. Thus, in this study, the efficacy of the process of electrocoagulation using iron and aluminium sacrificial electrodes has been evaluated for Chemical Oxygen Demand (COD) removal and Ammonia-Nitrogen (NH3-N) removal from landfill leachate. Different operating conditions were studied for the removal of COD and NH3-N which includes inter-electrode distance, current density, pH and operating time. The results of the batch experiments showed a maximum COD removal of 100% using iron electrodes at the optimum operating conditions of current density of 3 mA/cm2, electrolysis time of 30 minutes and inter-electrode distance of 2 cm. Whereas the maximum NH3-N removal of 99.83% using aluminium electrodes at the optimum operating conditions of current density of 2 mA/cm2, electrolysis time of 45 minutes and inter-electrode distance of 4 cm. Treatment of landfill leachate wastewater by electrocoagulation process using an aluminium and iron electrode was investigated in a batch electrochemical cell reactor. Response surface methodology based on central composite design was used to optimize the operating parameters for the removal of % COD and % ammoniacal nitrogen (NH3-N) together with power consumption from landfill leachate. Effects of three important independent parameters such as current density (X1), electrocoagulation time (X2), and solution pH (X3) of the landfill leachate sample on the % COD and % ammoniacal nitrogen (NH3-N) removal with power consumption were investigated. A quadratic model was used to predict the % COD and % ammoniacal nitrogen (NH3-N) removal with power consumption in different experimental conditions. The significance of each independent variable was calculated by analysis of variance. In order to achieve the maximum % COD and % ammoniacal nitrogen (NH3-N) removal with minimum of power consumption, the optimum conditions were about current density (X1) 2 mA/cm2, electrocoagulation time (X2) 20.683 minutes and initial solution of effluent pH (X3) 7, with the yield of COD removal of 72.694%, and ammoniacal nitrogen (NH3-N) removal of 86.025% when the inter electrode distance was 4cm and aluminium electrode was used. The electrocoagulation process could be applied to remove pollutants from industrial effluents and wastewater.