ABSTRACT: Sol id waste dumping on land is the most practical and economical method among other solid waste treatment methods. However, the leachate generated from these areas is a significant environmental hazard. The landfıll leachate is usually high strength wastewater with high chemical oxygen demand (COD), biochemicaloxygen demand (BOD) values, as welli as with high ammonium ion concentrations. The objective of this study is to investigate the capacity of natura zeolite (clinoptilolite) to remove ammonium ions present in landfıll leachate under both batch andjlow-through conditions. The ammonium adsorption capacity of zeolites from Bigadiç and Gördes area in Turkey was tested with respect to ammonium concentration in leachate and zeolite partide size. Ammonium adsorption increased with decreasing partide size. On the other hand, both zeolite types exhibited similar ammonia nitrogen (NH3-N) removing capacity. Ammonium adsorption capacity increased with increased ammonium concentration in the leachate. it was observed that ammonium exchange capacity of the zeolites was reduced due to the competition with coexisting cations present in the leachate.