Acute Toxicity Test of Landfill Leachates Using Protozoan Communities

Leachate contains high concentrations of organic matter, ammonia, metals, and other toxic compounds, which may pose serious risks to ecosystems and human health. In order to set up the appropriate toxicological criteria for the leachate, leachate toxicity tests with various organisms need to be conducted. The objective of this investigation was to evaluate the toxicity of leachate using the protozoan community, and the toxic effects of varies seasonal leachates were also compared. Leachates from two municipal solid waste landfills in Wuhan, China were used to develop short-term acute toxicity testing. Bioassays were conducted recording toxicity against various seasonal protozoan communities as median effective concentrations (EC₅₀ values) of species after 24 h exposure. Various seasonal protozoan communities were all sensitive to the leachate samples and the species of the communities decreased with an increase in the leachates concentrations. The EC₅₀ values of Landfill A oscillated between 1.03% and 2.24%, and the EC₅₀ values of Landfill B were between 2.79% and 6.60%. Fluctuation of physicochemical parameters and EC₅₀s of leachates depended rather on landfill age than season of the year (seasonal variations). The results from the bivariate correlation analyses between EC₅₀s and physicochemical parameters implied that the toxicity of leachate might reliably depend on the chemical oxygen demand (COD) and ammonia nitrogen (NH₄⁺-N).