Degradation of organic compounds in a municipal landfill leachate treated in a suspended‐carrier biofilm process

Abstract

Leachate from a Swedish municipal landfill was analyzed for organic compounds before and after biological treatment in a pilot plant. The treatment consisted of two stages: one aerobic (nitrification) and one anoxic (denitrification), both working as suspended‐carrier biofilm processes. The chemical oxygen demand reduction in the aerobic stage was 15 to 30% during the study. Ultrafiltration and gel filtration chromatography studies showed that mainly organic compounds with a low molecular weight were degraded during treatment; however, a fraction of these low‐molecular‐weight compounds was still left after treatment. Furthermore, reversed‐phase chromatography analyses indicated that a large part of the hydrophilic fractions of the organic compounds were unaffected by the treatment. Gas chromatography–mass spectrometry analyses showed that the leachate contained low concentrations of plasticizers and polycyclic aromatic hydrocarbons. Toxicity tests indicated that much, but not all, of the toxicity depended on the high ammonium ion concentration in the untreated leachate.