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Intermediate covering of municipal solid waste landfills with alkaline grits, dregs and lime mud by-products of kraft pulp production

2019; Elsevier BV; Volume: 239; Linguagem: Inglês

10.1016/j.jclepro.2019.117985

1879-1786

Rogério Machado Pinto Farage, Cláudio Silva, Ana Augusta Passos Rezende, José João Lelis Leal de Souza, Antônio Teixeira de Matos, Antônio José Vinha Zanuncio,

Phosphorus and nutrient management

The increasing demand for intermediate covering materials in municipal solid waste landfills stimulates studies for finding alternative materials for this purpose. This study evaluates the use of dregs and grits and of lime mud generated in kraft pulp mills in considerably large volumes as covering materials in municipal solid waste landfills. Emphasis was given to the generated leachate quality and effects on the microbiological activities within the landfill cells. Three experimental units simulating landfill cells, 3 m high and 1 m in diameter, were assembled and monitored during 6 months. Unit 1 (U1) was filled with municipal solid waste (MSW), and a mixture of dregs and grits in a proportion of 70% and 30%, respectively, was used as covering material. Unit 2 (U2) used lime mud as covering material, and Unit 3 (U3) was filled solely with MSW without any covering material, as a control. The concentration of the leachate's Chemical Oxygen Demand (COD) decreased by 91% and 92%, respectively, for U2 and U3: a decrease was not observed for U1, which remained above 30,000 mg/L, until the end of the six-month monitoring interval. Nine months after this interval, the COD decrease for U1, U2 and U3 was 92%, 98% and 97%, respectively. The metal concentrations in the leachates of the three experimental units were below the legal limits for discharge into watercourses in Brazil. The substitution of soil by the mixtures of dregs and grits and lime mud proved to be technically feasible, but the concentration of sodium in the leachate produced in Unit U1 (12,480 mg/L) was 13 times higher than U3 (control unit) and should be taken into consideration. This fact may have caused inhibition of the bioactivity in the cell and thus delayed the degradation of organic matter.