Autotrophic nitrification and denitrification characteristics of an upflow biological aerated filter

Wastewater nitrification was carried out using a laboratory-scale upflow biological aerated filter (BAF) packed with a polyurethane-based porous medium. The filtration medium has macropores which provide a greater surface area for the development of biofilms. The macro-pores have both aerobic and anaerobic zones, depending on the depth of oxygen penetration in the medium. Wastewater ammonium was oxidized at a maximum rate of 1.8 kg NH4+ m(-3)d(-1) and showed more than 90% nitrification efficiency in the BAF. During the biological nitrification of wastewater, considerable nitrogen loss was observed in the BAF under oxygen-limited conditions when organic carbons were not provided for denitrification. Most probably, the lost nitrogen was converted to gaseous nitrogen compounds including dinitrogen by autotrophic dentrification and anaerobic ammonium oxidation. (C) 2001 Society of Chemical Industry.