The purpose of this research project was to study the biological treatability of a leachate from an “older” landfill, with specific regard to the removal of ammonia by nitrification and denitrification. A single sludge denitrification system with recycle was used. Leachate ammonia concentrations of up to 288 mg/L-N were reduced to less than 1 mg/L. The ammonia was removed by nitrification and bacterial uptake. Glucose was added to aid denitrification. The degree of denitrification was dependent on the glucose loading to the anoxic reactor. The influent leachate COD removal was 20%; however after the addition of glucose to the system, a mean COD removal of 74% was obtained. The four metals monitored, zinc, manganese, nickel and iron were removed by the biomass, but not to the same extent. At the metal concentrations observed, there was no inhibitory/toxic effect to the ammonia removal system employed.