Assessment of landfill leachate toxicity reduction after biological treatment.

In the present article, the efficiency of biological treatment of landfill leachates was evaluated by implementation of physicochemical characterisation and a complex toxicity assessment. An array of toxicity tests using bacterium Vibrio fischeri, alga Desmodesmus subspicatus, crustacean Daphnia magna, and embryo of fish Danio rerio, as well as unconventional methods using biochemical biomarkers (protein content, enzymes cholinesterase, and glutathione-S-transferase), were employed. Toxicity of leachates varied depending on the season of collection in relation to their different physicochemical characteristics. Uncommon effects of leachates on organisms, such as hormetic-like increases of algal growth and reproduction of daphnids, were identified. New approaches using the activities of enzymes were found unsuitable for routine hazard assessment of leachates. Although physicochemical parameters and toxicity decreased significantly after biological treatment, the effluents did not meet the demands of the current Slovenian legislation; thus, the existing biological treatment was found inappropriate. The development of advanced treatment techniques for landfill leachates is thus encouraged.