Autotrophic nitrification and denitrification characteristics of an upflowbiological aerated filter

Wastewater nitrification was carried out using a laboratory-scale upflow bi ological aerated filter (BAF) packed with a polyurethane-based porous mediu m. The filtration medium has macropores which provide a greater surface are a for the development of biofilms. The macro-pores have both aerobic and an aerobic 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 obse rved in the BAF under oxygen-limited conditions when organic carbons were n ot provided for denitrification. Most probably, the lost nitrogen was conve rted to gaseous nitrogen compounds including dinitrogen by autotrophic dent rification and anaerobic ammonium oxidation. (C) 2001 Society of Chemical I ndustry.