NITROGEN LOSS IN A NITRIFYING ROTATING CONTACTOR TREATING AMMONIUM RICH LEACHATE WITHOUT ORGANIC-CARBON

Extended loss (up to 70%) of nitrogen is observed in a nitrifying rota ting biological contactor (RBC) treating ammonium - rich leachate of a hazardous waste landfill. Due to pretreatment (flocculation, POD-remo val activated carbon) DOC was less than 20 mg/l so heterotrophic denit rification can be excluded. The nitrification rate reaches 3-4 g NH4-N m(-2) d(-1) at a pH of 7-7.3 in the first two of three RBC compartmen ts. An increasing partial pressure of oxygen and ammonium concentratio n favor nitrogen removal over ammonium oxidation. The reduction of nit rite produced in the aerobic biofilm layer close to the surface might therefore be coupled with ammonium oxidation and takes place in the de eper or temporarily anoxic layer of the biofilm. (C) 1998 IAWQ. Publis hed by Elsevier Science Ltd.