Anaerobic treatment of a municipal landfill leachate

Abstract

Leachate from a municipal landfill site was treated in a laboratory using fixed-film cultures under anaerobic conditions. Serum-bottle cultures were used for optimization of the growth parameters. The reduction of the chemical oxygen demand (COD) of the leachate was faster at 29 °C compared with lower temperatures. Gradual acclimation of the microbial population to temperatures as low as 4 °C considerably increased the rate of COD removal at these temperatures. Addition of supplements to the leachate was not needed and it was not necessary to adjust the pH (5.9) for optimal COD reduction. Continuously fed reactors were also used to treat the leachate. The maximum organic loading rate of the reactor at 22 °C to obtain 85% COD removal was 2.1 kg COD∙m−3∙day−1, which corresponded to an hydraulic retention time of 1.5 days. After treatment under these conditions, the toxicity (Microtox method) of the leachate was completely eliminated and the required quality standards were met for iron, oil and grease, and phenols. The fermentative microorganisms in the biofilm of the reactor were evaluated to 4.6 × 107cells∙cm−2and identified as Streptococcus gallinarum, Clostridium glycolicum, Clostridium bifermentans or sadallii, Citrobacter amalonaticus, Bacteroides capillosus, and Eubacterium sp.Key words: anaerobic treatment, landfill, leachate, growth parameters, fixed-film reactor, microbiology.