Avaliação geotécnica de misturas de solo e composto orgânico para uso como biocoberturas em aterros sanitários.

Abstract

The landfill cover layer in Brazil is generally characterized as a conventional layer consisting of compacted soil, which can act as a physical, chemical or biological barrier. However, due to the weather conditions, with wetting and drying cycles, especially in semi-arid regions, layers of compacted soil for landfills eventually lose their efficiency, resulting in the escape of gas into the atmosphere and the impairment of environmental quality. The addition of organic compost to landfill covers may be economically and environmentally feasible, including reducing the required amount of soils from the deposits. Another important factor is that organic material, such as pruning residues from several sources, can be used as organic compost and incorporated to the soil, improving the geotechnical characteristics of the cover layers. Therefore, the objective of this research is to evaluate the geotechnical properties of soil and organic soil-compost mixtures, in proportions of 1: 1 and 3: 1, by weight, aiming the use of biocovers in landfills. For this purpose, the collection and characterization of the soil cover layer in the cell 2 from the Campina Grande (PB) Landfill was done, the defined organic soil-compost mixtures, the physicochemical analyzes as well as the obtaining of the moisture retention curves, with analyzes of the adjustments of the experimental points of the curves to the models proposed in the literature. The collection of soil samples in the cover layer was obtained at certain points through the Limit Central Theorem. The results showed that the addition of organic compost to the soil in all proportions modified the geotechnical properties, reducing compaction, increasing liquidity limits, permeability and also the moisture retention capacity. In addition, in relation to the granulometric distribution, the 1: 1 mixture presented a well-graded mixture, in relation to the other samples, and an increase in the percentage of coarse particles, mainly sand, was verified with the addition of compound organic. The adjustment of the Van Genuchten curve to the experimental points of the retention curve met the conditions of agreement from the analyzed statistical parameters, for all the samples, with better results for the 1: 1 mixture. It was also found that there was no significant change in the unsaturated hydraulic conductivity with the addition of the organic compound. In relation to the physico-chemical characteristics, it was observed that the addition of organic compound contributed to the increase of the organic matter content, macronutrient content, pH and Cation Exchange Capability in the samples, especially in the 1: 1 mixture. It can be concluded that among the mixtures studied, 1: 1 presented better results in relation to the aspects related to the use of biocovers, however it is suggested the use of the mixture of type 3: 1, because for some geotechnical parameters it was adequate, besides being more feasible, since pruning waste in high quantities is not always available in landfills. This study can still be extended to landfills with similar characteristics to the Landfill in Campina Grande - PB, in terms of meteorological conditions and types of residues.