Uso de resíduo sólido de lodo de esgoto no cultivo de beterraba (Beta vulgaris esculenta) e alface (Lactuca sativa)

Abstract

Sewage sludge is a byproduct of wastewater treatment produced in large quantities. Rich in organic matter and nutrients, sewage sludge is a good source of organic fertilizer. However, the amount of heavy metals and pathogenic microorganisms present in its composition is a limiting factor, which makes its destination and final disposal even more difficult. In this sense, the objective of this study was to evaluate the effects of applying lime-stabilized sewage sludge as an alternative way for the final disposal of sewage sludge. Beetroot (Beta vulgaris esculenta) and lettuce (Lactuca sativa) were cultivated using the biosolid. The availability of arsenic, cadmium, copper, chromium, mercury and zinc metals in leaves, roots/tubercles and in the cultivation soil was evaluated. Nitrogen and phosphorus levels were also evaluated as a source of nutrients for crop development. Five treatments were carried out with increasing doses of biosolid (T1, T2, T3, T4 and T5) and the control (C) each treatment was composed of 8 units of lettuce or beet seedlings. The treatment of the biosolid with lime reduced the amount of pathogens and heavy metals, and the results obtained in the chemical characterization after treatment are in accordance with CONAMA 498/2020. The values of nitrogen and phosphorus after treatment as a source of nutrients were satisfactory for a good development of the cultures in question. The values found for the metals arsenic, cadmium, copper, chromium, mercury and zinc for treatments T1, T2 and T3 on lettuce and beet leaves are in accordance with legislation IN 160/2022. On the other hand, the roots/tubers of the beet did not develop properly and the values of heavy metals are above the IN 160/2022 legislation. In treatments T4 and T5, the cultivars did not survive the biosolid doses applied. With these results, we observed that the sewage sludge treated with lime is a promising source of low-cost alternative organic fertilizer for planting vegetables, tubers.