Potential application of chilean natural zeolite as a support medium in treatmentwetlands for removing ammonium and phosphate from wastewater

Abstract

This study aims to evaluate the sorption characteristics of NH4+-N and PO43--P onto the surface of natural zeolites coming from Chile and their potential application in the subsurface-flow treatment wetlands for wastewater treatment in rural areas. For this purpose, adsorption experiments onto the zeolite were developed in batch assays. The effects of the adsorbent quantity (20 g and 50 g) and particle size (0.2-1.0 mm; 1.5-3.0 mm, and 5.0-8.0 mm) were evaluated in terms of adsorption capacity at different NH4+-N and PO4-3-P concentrations. Then, the obtained laboratory results were adjusted to theoretical models: Saturation-growth-rate and Langmuir. The saturation adsorption of NH4+-N on the zeolite increases at the same time that the initial concentration increases for the same zeolite quantity; however, the saturation values were similar between the different zeolite sizes tested. For PO4-3-P, the adsorption did not have a direct relationship with the initial concentration nor zeolite quantity and better results were only achieved for zeolite sizes of 1.5-3.0 mm. Regarding the Langmuir model, sizes of 1.5-3.0 mm had the best adsorption characteristics, with the maximum adsorption capacity of up to 1.58 mg/g for NH4+-N and up to 0.08 mg/g for PO4-3-R Therefore, a new material-a natural zeolite from the Maule Region of Chile-is described as a potential support medium for treatment wetlands.