Identificação de compostos orgânicos e avaliação da toxicidade de lixiviado de aterro sanitário “in natura” e tratado por Fenton

Abstract

Landfill leachate is a complex liquid residue of varied composition, characterized by high concentrations of organic and inorganic compounds, recalcitrant and highly toxic. Because of their high polluting potential, leachates must be treated prior to their release. Advanced oxidative processes, specifically the Fenton process, are considered promising for the treatment of landfill leachate, since they are capable of oxidizing a wide range of compounds of difficult degradation by mineralizing them in CO2, H2O and inorganic ions or by making them more readily biodegradable substances. The present study aimed to evaluate the employability of the Fenton process in the treatment of leachate from the metropolitan sanitary landfill of. The leachate, before and after treatment, was characterized by physical-chemical parameters and identification of organic compounds using GC-MS. In addition, toxicity tests were used. To determine the toxicity, tests were carried out to inhibit dissolved oxygen consumption and inhibition in biogas production, as well as acute toxicity tests involving D. magna and L. sativa. Removals of 90% for color, 86% for COD and 56% for Abs254 were obtained in the Fenton process, pH 2.0, iron concentrations of 12 gL^-1 and ratio [H2O2]: [Fe^2 +] equal to 9. Inorganic leachate and Fenton effluent samples were identified as being 43 organic compounds, of which 63% were removed by the oxidative process and 15 compounds were identified as by-products of the oxidation, being present in the Fenton effluent. By toxicity testing, toxicity effects were observed on all test organisms evaluated when using "in natura" leachate samples. The Fenton process was considered efficient in reducing toxicity to aerobic organisms, with no TCO reductions observed in any of the evaluated ratios. As for toxicity to anaerobic organisms, the results of the BMP test showed significant reductions in the toxic potential of the leachate after the oxidative treatment, only in the proportion of 10% of the Fenton effluent levels of inhibition above 50% in the biogas production in relation to the control, at the end of 70 days, were observed. For microcrustacean D. magna, although it shows a reduction in toxicity (the treated sample was three times less toxic than the "in natura" sample), the effluent from the Fenton process is classified as slightly toxic (EC50 21,96). The results indicated a phytotoxicity in L. sativa, when exposed to low concentrations of treated leachate (25%), an inhibition above 58% was observed, reaffirming the toxic potential of the leachate even after oxidative treatment. The results indicate that the treatment of landfill leachate by Fenton process even with high removal efficiencies of physico-chemical parameters did not produce a non-toxic effluent for all test organisms.