ANAEROBIC TREATMENT OF A MUNICIPAL LANDFILL LEACHATE

Leachate from a municipal landfill site was treated in a laboratory us ing fixed-film cultures under anaerobic conditions. Serum-bottle cultu res were used for optimization of the growth parameters. The reduction of the chemical oxygen demand (COD) of the leachate was faster at 29 degrees C compared with lower temperatures. Gradual acclimation of the microbial population to temperatures as low as 4 degrees C considerab ly increased the rate of COD removal at these temperatures. Addition o f supplements to the leachate was not needed and it was not necessary to adjust the pH (5.9) for optimal COD reduction. Continuously fed rea ctors were also used to treat the leachate. The maximum organic loadin g rate of the reactor at 22 degrees C to obtain 85% COD removal was 2. 1 kg COD . m(-3) . day(-1), which corresponded to an hydraulic retenti on time of 1.5 days. After treatment under these conditions, the toxic ity (Microtox method) of the leachate was completely eliminated and th e required quality standards were met for iron, oil and grease, and ph enols. The fermentative microorganisms in the biofilm of the reactor w ere evaluated to 4.6 X 10(7) cells . cm(-2) and identified as Streptoc occus gallinarum, Clostridium glycolicum, Clostridium bifermentans or sadallii, Citrobacter amalonaticus, Bacteroides capillosus, and Eubact erium sp.