Biological treatment of leachate from the uncontrolled landfill: evaluation of toxicity and heavy metals reduction

ABSTRACT This work assesses the efficiency of biological processes in reducing leachate toxicity, using tests of phytotoxicity, cytotoxicity and heavy metals assay. Concerning metal load of raw leachate, iron is the most abundant with a value of 77.23 mg/L; combined treatment is most effective in reducing metals with abatement rates of: Al (94.96%), Fe (99.23%), Pb (90.53%), Sn (90.25%) and Zn (90.43%). The phytotoxicity of raw leachate is total against all tested seeds, this phytotoxicity was decreased after treatment with SBR, and the germination indices are between 3.60%−65.36%, 0.25%−39.99% and 5.36%−35.55% respectively for Daucus carota, Lactuca sativa and Hordeum vulgare seeds. Leachate treated with the combined treatment exhibits no inhibition of germination even at concentrations of 100%. Regarding cytotoxicity assessed via Brine Shrimp test, raw leachates were cytotoxic killing all Artemia salina larvae even at low concentration of 1%. After the treatments, cytotoxicity of leachate was decreased especially in leachate treated by SBR and combination with inhibition percentages up to 16.66%. The experimental results obtained were confirmed using PCA which showed that the SBR and combination treatments have common purification characteristics and also the inverse correlation between heavy metal concentrations and germination indices indicate that these metals are involved in leachate toxicity.