Simultaneous nitrification/denitrification in an aerobic biofilm system

In the biological pretreatment of landfill leachate in Mechernich (Germany) a loss of inorganic nitrogen of up to 90% was observed in the nitrification step (rotating biological contactor) under low DO conditions. Ammonia was removed but only small amounts of nitrate were produced. Nitrite accumulation did not occur. In aerobic batch tests nitrogen loss was confirmed without any addition of organic substrate, even when homogenizing the biofilm mechanically-to destroy possible anoxic microzones. N-2 was measured as the gaseous end product of the process. From results presented it can be assumed that a largely autotrophic microorganism population performed this aerobic nitrification/denitrification. (C) 1998 IAWQ. Published by Elsevier Science Ltd.