To develop an effective technique for enhancing the removal efficiency of ammonium and phosphate at low concentrations without losing potential removal capacity, Na-ZFA (zeolite synthesized from fly ash) was converted into Ca, Mg-, Al-, and Fe-ZFA by salt treatment and the simultaneous removal of ammonium and phosphate by ZFA saturated with different cations was investigated. It was shown that Al3+-ZFA had the highest removal efficiencies (80-98%) for ammonium, followed by Mg2+ (43-58%), Ca2+ (40-54%), Na+ (< 20%), and Fe3+ (< 1%). Both alkaline pH values (in the cases of Na+, Ca2+, Mg2+) and acidic pH value (in the case of Fe3+) inhibited the sequestration of ammonium. At low initial phosphate concentrations, the efficiency of phosphate removal by Al3+-and Fe3+-ZFA approached 100%, followed by Ca2+ (60-85%), Na+ (< 25%), and Mg2+ (< 5%). The difference in phosphate removal efficiency was explained by the adsorption mechanisms. It was concluded that ZFA could be used in simultaneous removal of NH4+ and phosphate at low concentrations with presaturation by an appropriate cation such as 4 Al3+ through salt treatment. (c) 2006 Elsevier Inc. All rights reserved.