Ecotoxicity Assessment of Landfill Leachates using a Battery of Bioassay and Toxicity Characterization of the Leachates
Abstract : The western part of Teshima Island in the Seto Inland Sea (Japan) had been used as an illegal dumping ground for more than 10 years and the accumulated waste was estimated to be about 510.000 tons. There has been no systematic toxicity assessment conducted on this waste. In this study, a battery of bioassays was applied to the collected leachates. Toxicity of the leachates was evaluated using the Microtox test, umu test (a mutagenicity assay), yeast inhibition zone test, acute lethality tests using crustaceans, and root elongation test using lettuce. The landfill leachates collected at 4 sites on November 7, 1996 were filtered through 0.45 and 0.2 µm filters sequentially. All samples were highly toxic to crustaceans and lettuce, but showed a weak or no toxicity to three kinds of test microorganisms.All samples were also found to have no mutagenic activity, but to have high concentrations of TOC, TN, NH4, Cl, SO4and low levels of heavy metals. Four leachates retained their toxicity to lettuce, despite a 6-months storage at 4° C.
These samples were subject to further toxicity characterization. The results indicated that the toxicity of sample No. 1 could be reduced by aeration, solid phase extraction, autoclaving, and UV-C irradiation. This implies the causative toxicants being some volatile, heat- and photo-degradable nonpolar organics. The toxicity reduction in samples No. 2 and 3 could be only achieved through solid phase extraction. Our study has clearly showed that a systematic identification of toxicants in all leachates samples is needed in the management of toxicity reduction in landfill leachates