Hydraulic conductivity and soil-sewage sludge interactions

Abstract

One of the main problems faced by humanity is pollution caused by residues resulting from the production and use of goods, e.g, sewage sludge. Among the various alternatives for its disposal, the agricultural use seems promising. The purpose of this study was to evaluate the hydraulic conductivity and interaction of soil with sandy-silty texture, classified as Spodosols, from the Experimental Station Itapirema -IPA, in Goiana, state of Pernambuco, in mixtures with sewage sludge from the Mangueira Sewage Treatment Station, in the city of Recife, Pernambuco at rates of 25, 50 and 75 Mg ha -1 . Tests were conducted to let water percolate the natural saturated soil and soil-sludge mixtures to characterize their physical, chemical, and microstructural properties as well as hydraulic conductivity. Statistical data analysis showed that the presence of sewage sludge in soils leads to an increase of the < 0.005 mm fraction, reduction in real specific weight and variation in optimum moisture content from 11.60 to 12.90 % and apparent specific dry weight from 17.10 and 17.50 kN m -3 . In the sludge-soil mixture, the quartz grains were covered by sludge and filling of the empty soil macropores between grains. There were changes in the chemical characteristics of soil and effluent due to sewage sludge addition and a small decrease in hydraulic conductivity. The results indicate the possibility that soil acidity influenced the concentrations of the elements found in the leachate, showing higher levels at higher sludge doses. It can be concluded that the leaching degree of potentially toxic elements from the sewage sludge treatments does not harm the environment.

Codisposição de lodos de tratamento de esgotos em aterros sanitários brasileiros: aspectos técnicos e critérios mínimos de aplicação

“…Os aterros de resíduos têm sido projetados, em termos de segurança estrutural, segundo os princípios da mecânica dos solos, considerando-se cada tipo de resíduo como nova unidade geotécnica. Embora pesquisas venham sendo realizadas sobre o comportamento geotécnico do lodo de ETE (BRINGHENTI, 1998;FERREIRA, 2010;FERREIRA et al, 2011;AGODA-TANDJAWA et al, 2013; entre outros), o nível de conhecimento das características e das propriedades geotécnicas desse lodo, para diferentes tipos e níveis de secagem, ainda é limitado (O'KELLY, 2006).…”