engleski

The suitability of sewage sludge for soil amendment in relation to its metal and radionuclide levels

The aim of this study was to evaluate the suitability of sewage sludge for soil amendment in relation to its metal and radionuclide levels. The macronutrients were assayed as they may affect the retention of contaminants by sludge biomass. In the dewatered sewage sludge, the contents of total N, P and K were determined using the ISO recommended procedures. Concentrations of total Cd, Ni, Zn were measured using the ICP-OES, while 238U and 226Ra by gamma-ray spectrometry. The results showed that N contents ranging from 0.4–7.7%, while the amounts of P and K were within the limits from 3.2–36.1 and 0.8–4.7 g kg-1 d.w., respectively. Concentrations of Cd, Ni and Zn varied from 0.3–1.3, 7.9–52.6 and 95.7–1254.0 mg kg-1 d.w., respectively, which is below the threshold limits according to Croatia's legislative on sewage sludge agricultural use. Concentrations of 238U and 226Ra, which ranged from 8.7–59.1, and 3.2–44.5 Bq kg-1 d.w., respectively, are in the area of a natural background. Furthermore, the correlations between the N and Cd (r = 0.755) and P and 238U (r = 0.668) indicate that macronutrient compounds may be involved in adsorption of metal contaminants by municipal sludge. According to obtained results it seems that studied municipal bio-solids may be applied to soil considering the legislative-based recommendation. Soil conditioning with sewage sludge may be a promising strategy for nutrient recycling from municipal waste.

soil amendment, sewage sludge, macronutrients, metals, radionuclides

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