Strategy for Complete Nitrogen Removal in Bioreactor Landfills

Waste acclimation and batch microcosm studies containing digested municipal solid waste were conducted at different temperatures (22, 35, and 45°C ) and gas-phase oxygen concentrations (0.7–100%, by volume) to provide guidance for field-scale implementation of in situ nitrogen removal processes. Results demonstrate that in situ ammonia–nitrogen is feasible in decomposed aerated solid waste environments at the gas-phase oxygen concentrations and temperatures evaluated and the potential for simultaneous nitrification and denitrification in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. Small amounts of oxygen were found sufficient for nitrification/ammonia removal to proceed, although removal rates increase with oxygen concentration. Laboratory results suggest field-scale implementation of in situ nitrogen removal occur in small dedicated treatment zones containing previously degraded waste (later in the life of a bioreactor landfill). Model simulations indicate removal of ammonia–nitrogen to low levels can occur with relatively short aeration depths (depth estimates ranged from 1.6 to 7.2m below the point of leachate injection). Field-scale verification of these depth estimates is required prior to routine acceptance.