Electrochemical Removal of Ammonia in Wastewater.

Abstract

The principal objective of wastewater treatment is to allow human and industrial effluents to be disposed of without any danger to human health or unacceptable damage to the natural environment. The composition of wastewater can be complicated depending on the purpose and it contains organic matters, ammonia, phenols, cyanide and other aromatic organics which are treated with coagulation, oxidation, adsorption, and etc. However, the main disadvantage of these technologies is that they are lacking of effectiveness if applied individually. For example, biological treatment is the most common and oldest treatment process used to treat municipal and industrial wastewater to produce high degree of purity quality of the effluent, but these systems are generally energy intensive and require high investment, maintenance, operating costs, and also produce large amount of sludge, which itself requires treatment. In addition, these systems cannot be employed for the most of the industrial effluents since they are bio-toxical and recalcitrant to biodegradation, so fails to eliminate chemical oxygen demand, ammonia and color such as textile wastewater. Recently, the electrochemical treatment technique has been considered as a promising alternative for the treatment of wastewater due to its unique advantages such as high treatment efficiency, environmental compatibility, versatility, robustness, and amenability to automation. In this study, the focus is given to the direct electrochemical oxidation of ammonia in wastewater since this process has shown that is very effective, compact and economically practical compared to other technologies. In this context, an electrochemical reactor designed which consists of a graphite felt working electrode and a counter electrode and a saturated Ag/AgCl electrode as reference electrode and operated under batch mode with recirculation at a flow rate of 10 ml/min. The potential of working electrode was controlled relative to reference electrode using a potentiostat. To study the rate of anodic oxidation of wastewater, the working electrode was polarized at 2V versus Ag/AgCl. The electrochemical cells was sampled every 30 minutes to monitor ammonia (NH4 + ) concentration. After 4 hours of treatment, only 21.9% of ammonia is oxidized via electrochemical oxidation. Given the results of the study of ammonia oxidation were confirmed that the oxidation of ammonia are possible with direct anodic oxidation and proved that electrochemically NH4 + removal an alternative method to biological nitrification.