Estimation of the hazard of landfills through toxicity testing of leachates—I. Determination of leachate toxicity with a battery of acute tests

Twenty-seven landfill leachates were tested on a battery of conventional toxicity tests (microalgae, daphnids, duckweeds) and new microbiotests (rotifers, crustaceans, protozoans, luminescent bacteria). The toxicity varied substantially from one test species to the other, from one site to the other, as well as from one type of landfill to the other. Leachates of domestic wastes were significantly more toxic than those of pure industrial wastes; the most toxic leachates were found for landfills receiving hazardous industrial wastes mixed with domestic wastes. The highest sensitivity was found for the protozoan assay, followed by the crustacean microbiotests. All other types of bioassays appeared to be substantially less sensitive to the toxicants present in the landfill leachates. The results of a Principal Component Analysis suggest that in approximately 90% of the cases the toxicity of landfill leachates can be assessed by applying a test battery composed of a bacterial assay, a protozoan test and an assay with micro-algae, jointly with one of the following bioassays: higher plants, rotifers or crustaceans. The application of a factor 100 to to the highest toxicity figure for each landfill leachate to extrapolate a Predicted No-Effect Concentration (PNEC) revealed that in quite a number of cases, the leachates need to be diluted by more than 10.000 times to make them innocuous for environmental biota.