Determinação de variáveis hidráulicas e do potencial poluidor da massa de resíduos sólidos urbanos com diferentes porcentagens de matéria orgânica e massa específica

Abstract

The great generation of municipal solid waste (MSW) is among the most significant and representative environmental challenges faced by the country. It is a highly heterogeneous material, which the hydraulic properties, and polluting potential of byproducts generated by biological decomposition vary widely depending on the characteristics of the waste, what makes the project development of landfill and leachate treatment systems more difficult to be done. In this context, this study had as objective to evaluate the influence of gravimetric composition and specific weight of MSW in the determination of hydraulic conductivity (K) and field capacity () through tests using large permeameters, as well as to evaluate pollution potential of leachate generated by MSW compacted into six lysimeters which were exposed to the environment. To determine hydraulic conductivity (K) and field capacity (θ), waste were separately collected, weighed, and then portions of it were mixed seeking to have 3 different gravimetric compositions with 20%, 40% and 60% Organic Matter (OM) percentage. Later, waste was compacted in the permeameters seeking to reach specific weights of 3 and 5kN m-3, in a total of 6 tests. To evaluate leachate potential of pollution, waste was compacted within 6 lysimeters varying the same physical characteristics for the test using the permeameters. After the test set up, leachate was collected every two weeks for analysis of physics and chemical parameters. It was obtained for the compacted waste at 5kN m-3, a hydraulic conductivity value of 3.57 x 105m s-1, 2.53 x 10-5m s-1 and 7.52 x 10-5m s-1 to the tests with 20%, 40% and 60% of OM, respectively. Unable to perform the test with 20% organic material compacted waste to 5 kN m-3. As for the waste with a specific weight of 3kN m-3, hydraulic conductivity varied from 4.33 x 10-4 ms-1, 4.10 x 10-4 ms-1 and 2.93 x 10-3 m s-1 to the tests with 20%, 40% and 60% of OM respectively. It was found a field capacity of 14.98% and 14.72% for MSW with a specific weight of 5kN m-3 and tests with 40% and 60% of OM, respectively, and equals to 9.17%, 8.77% and 9.25% for MSW with a specific weight of 3kN m-3 and tests with 20%, 40% and 60% of OM, respectively. In the 3 lysimeters filled with compacted MSW at 3kN m-3, and consequently filled with less OM than the 3 lysimeters with MSW at compaction of 5kN m-3, it was observed a gradual fall in the analyzed parameters, except for pH and lead which grew over time.The lysimeters with a specific weight of 5kN m-3 did not have a gradual fall, having fluctuations over time. Therefore, it could be concluded in this study that the hydraulic conductivity of MSW decreased while increasing specific weight, and field capacity increases when the MSW are more compacted. However, regarding the influence of gravimetric composition nothing can be inferred from these tests, it is needed more experiments with this variable. In the lysimeters, in general, it was observed that the higher the amount of OM, the greater the polluting potential of the leachate, showing a decrease over time.