Ammonium ion removal from wastewater using Australian natural zeolite: Batch equilibrium and kinetic studies

The removal of nutrients from wastewater is becoming increasingly important throughout the world. This paper reports work on batch equilibrium and kinetic laboratory studies conducted to establish the efficiency of ammonium ion removal from wastewater effluent using a natural zeolite from the Werris Creek region in New South Wales. Experiments were conducted using samples of secondary treated domestic wastewater effluent and synthetic wastewater (ammonium chloride solution). The amount of powdered zeolite added ranged from 5 to 50 g l(-1). Experiments were undertaken to characterise the zeolite in terms of its ion exchange capacity and rate of ammonium ion adsorption under various conditions. The effects of the amount of zeolite added, initial ammonium ion concentration arid pH of the sample on ammonium ion removal were studied. Results were analysed using existing ion exchange models. The results indicate that a significant reduction of N as NH, (up to 80%) can be achieved using batchwise addition of powdered natural zeolite to NH4Cl solution. The ammonium ion removal capacity from wastewater effluent using 5 g l(-1) zeolite is about 2 mg g(-1) (compared to 3.7 mg g(-1) from NH4Cl solution) for an initial ammonium ion concentration of 25 mg l(-1). The ammonium ion removal efficiency increases with higher initial ammonium ion concentration and is highest for pH 5.5. Two adsorption models were fitted to the equilibrium data. The Freundlich adsorption model gives a better fit than the Langmuir model in the range of pH studied (pH 4-7) suggesting lateral interactions between adsorbed ions. From kinetic experiments 90% of ammonium ion removal occurs within 10-15 minutes and equilibrium is reached within 1.5-2 hours.