Treatment of landfill leachate: Removal of ammonia by struvite formation

Abstract

This paper presents a study of ammoniacal nitrogen removal by chemical precipitation resulting in the formation of ammonium and magnesium phosphat (MgNH 4 PO 4 ·6H 2 O), known as struvite, from the leachate in the Delta A landfill, located in the city of Campinas, São Paulo, Brazil. After the addition of a magnesium source (MgCl 2 ·6H 2 O), and phosphorus (Na 2 HPO 4 ·12H 2 O), ammoniacal nitrogen was precipitated as highly insoluble salt. The removal of ammoniacal nitrogen from the leachate exceeded 85% when the reaction was performed at an initial pH of 10.0. The highest efficiencies were achieved when the molar ratio between the ions involved in the reaction, i.e., Mg 2+ :PO 4 3- :NH 4 +, was 1.2:1.0:1.0, respectively.