The characteristics of leachate from landfill disposal site vary according to the operational stage of the ladfill. Leachates from "old" landfills are often rich in ammonia nitrogen due to the hydrolysis and fermentation of nitrogenous fractions of biodegradable refuse substrates. The relative concentration accumulating as stabilization progresses is also influenced by washout as leachate is collected and removed for external treatment. However, in landfills operated as bioreactors with leachate containment, collection and in situ recirculation to accelerate decomposition of readily available organic fractions of the refuse, leachate ammonia nitrogen concentrations may accumulate to much higher levels. High leachate ammonia nitrogen concentrations in land-fill leachate have been reported~1, resulting in separate treatment challenges if direct discharge to either land or receiving waters is practiced.
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