Abstract

MIGUEIS, Daniel; RODRIGUES, Paula; ROBOREDO, Marta  and  SOUSA, João Ricardo. Effect of direct application of treated sludge on soil habitability: avoidance assays with Eisenia fetida. Rev. de Ciências Agrárias [online]. 2022, vol.45, n.4, pp.601-610.  Epub Dec 01, 2022. ISSN 0871-018X.  https://doi.org/10.19084/rca.28557.

The increasing urbanization and industrialization have promoted a considerable expansion in the production of sewage sludge, which it is important to recycle and valorise in the circular economy context, with soil application being a viable, low-cost alternative, due to its high fertilizing value. Tough the legal policies considered limit fixed quantities of heavy metals and pathogenic microorganisms, the direct application of these residues may potentiate risks to soil quality, since it does not consider the effects of different contaminants presence. The objective of this work is to evaluate the effect of direct application of sewage sludge, at different application rates (0, 2, 5 10, 15, 30 and 60 t/ha) on soil habitability, based on rapid tests defined by ISO guidelines, through the evaluation of the behaviour of Eisenia fetida. The results reveal no effects on the behaviour of E. fetida in all treatments studied with sewage sludge (p>0.05), with a percentage of negative avoidance varying between 40 and 60%, compared to the control group. These results are related to the low levels of heavy metals and to the improvement of the physical-chemical conditions of the soil, resulting in an increase attractiveness of the biological model used. Other studies, with other soils, bioindicators type and methodologies, with longer exposure time, will be necessary to validate the observed aptness.

Keywords : sewage sludge; Eisenia fetida; avoidance; pollution; soil.

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