The final leachate from a municipal landfill, using a wetland tertiary treatment system, and water in the receiving environment were chemically characterized and evaluated for acute and sublethal aquatic toxicity. In addition, the effects of leachate discharges on the benthic macroinvertebrate community were determined. Samples were not acutely toxic to rainbow trout (Oncorhynchus mykiss), Daphnia magna and Vibrio fischeri. There was no detrimental effect on the survival and reproduction of Ceriodaphnia dubia, although a slight effect on reproduction was detected in river water at the control station (700 m upstream). Moderate toxicity to Selenastrum capricornutum was detected at the control and at station #2 (40 m from the outfall). Ames tests revealed no mutagenic or cyto-toxic effects in the final leachate or in river water downstream. Benthic macroinvertebrate sampling revealed that the leachate discharge had a localized impact on community structure near the outfall, but by 50 m downstream, the conditions were approaching those upstream of the discharge point.

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