BIOLOGICAL NITROGEN REMOVAL FROM MUNICIPAL LANDFILL LEACHATE IN A PILOT-SCALE SUSPENDED CARRIER BIOFILM PROCESS

Leachate from a municipal landfill receiving both household and indust rial waste was treated in pilot scale suspended carrier biofilm reacto rs for removal of nitrogen and organic matter. Nitrification was studi ed in two parallel aerated reactors, filled to 60% (v/v) with two diff erent models of carrier media with specific surface areas of 210 and 3 90 m(2)/m(3) media, respectively. Denitrification was carried out in a mechanically stirred, anoxic reactor filled to 40% with the carrier m edia having a surface area of 210 m(2)/m(3). Nitrified leachate from o ne of the aerobic reactors was fed to the anoxic reactor together with external carbon source, initially acetic acid and later methanol, to promote denitrification. The leachate temperature varied between 10 an d 26 degrees C during the study. Nitrification proceeded well in this temperature range. The highest volumetric nitrification rate, 24 g N/m (3) reactor h (16 degrees C), was obtained for the media with the larg est surface area. The maximum denitrification rate with methanol as ca rbon source was approximately 55 g N/m(3) h. As the process had reache d optimal operation, inorganic nitrogen was almost completely removed and the removal of total nitrogen was approximately 90%. The chemical oxygen demand (COD) removal was around 20% during the study. (C) 1998 Elsevier Science Ltd. All rights reserved.