Formação de bolhas na geomembrana de lagoas de lixiviado em aterros sanitários

Abstract

Lagoons with HDPE geomembranes (GM) are essential for the storage and treatment of leachate from sanitary landfills. The barrier system of these reservoirs serves to prevent the leakage of the effluent. However, failures in the installation and/or operation of the lagoon can cause holes in the GM, resulting in leachate leakage. The contact of this effluent with the soil can lead to the formation of biogas and the subsequent formation of bubbles in the lagoon. This study inspected the GM of two leachate lagoons at the Aterro Metropolitano de Gramacho (upstream and south lagoons), analyzed the leachate, characterized the bubbles present in the upstream lagoon, and for this reservoir, assessed the properties of the geosynthetics used, characterized the holes found, and examined the soil beneath the GM. The results from the inspections of the two lagoons indicated nine holes in each of them. In the south lagoon, all holes were located at the base, while in the upstream lagoon, eight were at the base (bubble region) and one on the slope. With the exception of the hole on the slope, all other holes were due to the installation process of the GM. Soil samples collected below the GM showed concentrations of ammoniacal nitrogen, chloride, conductivity, sodium, and potassium much higher than the values found in the local soil, indicating contamination by leachate. The study concluded that the cause of the bubble formation was the presence of holes in the GM resulting from the lagoon's installation process. The impacts associated with the occurrence of bubbles were the increased area of leachate leakage relative to the size of the initial hole, soil contamination, and the exposure of the GM to stress conditions for prolonged periods, as well as factors such as high temperatures and UV radiation, which are associated with the premature aging of the geosynthetic material. Recommendations included: the definition of normative requirements in the country, establishing a barrier system compatible with the risk of leachate lagoons; the definition of the maximum action leakage rate for commissioning and operation of lagoons; and the mandatory inspection using the dipole method after installation and during the operation of the reservoirs. The implementation of these recommendations aligns with the Sustainable Development Goals (SDGs) 3, 6, 11, and 14.