Efeitos ecotoxicológicos de lixiviado de aterro sanitário bruto e tratado por destilação em Eisenia andrei

Abstract

Sanitary landfill leachate is highly polluting, with high concentrations of heavy metals and toxic substances. In Brazil, this effluent must meet the standards and conditions for releasing effluents present in Resolution nº 430 of CONAMA/2011 and, at the state level, Resolution n° 355 of CONSEMA/2017. However, leachate treatment is complex and requires the use of several treatment methods to obtain a leachate that can be discharged into water bodies. Distillation is a method that can be used to treat the leachate using alternative heat sources, such as the use of biogas or solar energy, and has already shown effectiveness in removing color, turbidity and COD from the raw leachate. Ecotoxicological tests are adequate to verify the effects that the post-treatment effluent causes on bioindicator organisms. Therefore, this study aims to investigate whether the distillation method reduces the toxic potential of leachate from a landfill using the earthworm Eisenia andrei as a test organism, representing the terrestrial environment susceptible to contamination with leachate. The raw leachate was collected from storage ponds at the landfill in Santa Maria, Rio Grande do Sul and the leachate was treated in a bench-mounted simple distillation scheme. The experiment was conducted by exposing 10 earthworms in containers with soil containing two types of leachate, raw and treated, in triplicate, and in four doses: 0.0% (control), 0.1%; 0.15%; 0.25% and 0.35% (v/v). At 7, 14 and 28 days of exposure, 3, 3 and 4 earthworms were collected, respectively, for later biochemical analysis. The results of this study show that the simple distillation method decreased the concentration and diversity of drugs and metals in the crude leachate, and reached national and student release standards for Cu, Zn, Fe and Mn. In the concentrations with crude leachate, there were no significant alterations in the activity of GST and AChE, and only alterations occurred in the concentrations with treated leachate. The same occurred with the level of hydrogen peroxide. It is believed that the simple distillation method decreased the toxicity of the raw leachate by decreasing or changing characteristics of the raw leachate. The levels of lipid peroxidation in the concentrations with crude leachate showed that there was oxidative damage in the earthworms not contained by the defense mechanisms of the GST enzyme. In the concentrations with treated leachate, the effect of hormeses occurred, increasing the activity of GST to AChE at the lowest concentration and decreasing the activity as the concentration increased. It is concluded that the simple distillation method is effective in the treatment with leachate, but it must be associated with other treatment methods, as it was not able to avoid effects on the earthworm Eisenia andrei.