Composting sewage sludge with green waste from tree pruning

Abstract

ABSTRACT:Sewage sludge (SS) has been widely used as organic fertilizer. However, its continuous use can cause imbalances in soil fertility as well as soil-water-plant system contamination.The study aimed to evaluate possible improvements in the chemical and microbiological characteristics of domestic SS, with low heavy metal contents and pathogens, through the composting process. Two composting piles were set up, based on an initial C/N ratio of 30:1, with successive layers of tree pruning waste and SS. The aeration of piles was performed by mechanical turnover when the temperature rose above 65 ºC. The piles were irrigated when the water content was less than 50 %. Composting was conducted for 120 days. Temperature, moisture content, pH, electrical conductivity (EC), carbon and nitrogen contents, and fecal coliforms were monitored during the composting. A reduction of 58 % in the EC of the compost (SSC) compared with SS was observed and the pH reduced from 7.8 to 6.6. There was an increase in the value of cation exchange capacity/carbon content (CEC/C) and carbon content. .In SSC, helminth eggs were eliminated, making application sustainable for agriculture purposes.

Solid Waste in Agricultural Soils: An Approach Based on Environmental Principles, Human Health, and Food Security

“…However, research has shown that applying these wastes to the soil may cause environmental problems due to the addition of excess N, pathogens, heavy metals [31][32][33][34], acidiication [35], and salinization of agricultural soils [36].…”

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“…Os compostos nutricionais com maiores teores em sua composição foram óxido de cálcio e sulfato, seguidos pelo pentóxido de fósforo. Moretti et al (2015) encontraram valores de grandeza semelhantes para composto de lodo de esgoto, na ordem de 18, 12 e 3 g kg -1 para NPK e 21, 3 e 5 g kg -1 para Ca, Mg e S. Entretanto, os resultados são discrepantes para K e S, os quais podem ser explicados devido à sazonalidade na composição física, química e biológica do esgoto bruto. …”

The Evaluation of Hazards to Man and the Environment during the Composting of Sewage Sludge

“…Composting is a controlled aerobic process where complex consortia of microorganisms, whose structure depends on environmental conditions and substrate composition, degrade the readily available organic components or transform them into stable humic-like compounds. A decrease in the content of organic pollutants and a reduction in the bioavailability of heavy metals have also been reported during composting [7][8][9][10]. In this context, composting may be considered as a preferred strategy for utilising sewage sludge [11].…”