Toxicidade de lodo de esgoto sanitário: subsídios para tomada de decisão ambientalmente correta antes da incorporação em solos agrícolas

Abstract

In the State of Parana, Brazil, the use of calcined sewage sludge (biosolids) without remediation as a fertilizer by corn producers is recurrent. In the present study, the chemical composition, pathogenic potential and toxic potential to vegetal sistem and Eisenia fetida of biosolid produced by a sludge generating unit located in the southwest of the state were evaluated. The analysis of heavy metals and pathogens, based on Resolution 498/2020 of the Brazilian National Council for the Environment, classified the residue as suitable for incorporation into crop soils in Brazil. Concentrations 100; 50; 25; 12.50 and 6.25% of the biosolid caused phytotoxicity to Lactuca sativa, Cucumis sativus, Trititcum aestivum and Allium cepa, however, germination and root elongation were beneficial in Zea mays L. In root meristems of A. cepa bulbs, the five concentrations caused disturbances in cell division and the 100% concentration caused significant cell death. All concentrations promoted swelling in onion bulb roots, in addition to drastic inhibition of the enzyme’s ascorbate peroxide and superoxide reductase, activation of the enzyme guaiacol peroxidase and lipid peroxidation in their meristems. In earthworms, biosolid concentrations in the soil scared away animals in high percentages. In the mortality test, the three highest concentrations caused the death of all earthworms, and at 12.50% the death of 41% of the animals. In the surviving animals, catalase and guaiacol were active, demonstrating ample production of ROS in their tissues. The toxicity results suggest a potent hazard of the biosolid to plants and soil organisms. It is imperative that the sludge generating units in Parana subsidize adequate management of the residue before its availability to farmers, since its routine use can drastically impact the survival of different species and compromise the entire associated trophic chain.