| Abstract [eng] |
Sewage sludge production is constantly growing across the world, while sustainable sewage sludge (SS) disposal is a major environmental problem. In European Union the predominant valorization of sewage sludge is agricultural or forestry reuse for soil fertilization or land reclamation/restoration. Sewage sludge secondary use in agriculture is actively promoted for soil quality improvement due to its high amount of organic matter and nutrients. Along with many advantages of SS application to soil, it has drawbacks such as non biodegradable heavy metals, various organic contaminants, pathogenic organisms. Soil contamination with heavy metals not only endangers ecosystems, but also poses human health risk. Biological remediation of contaminated soil offers significant economic, energy, environmental and social advantages compared to traditional (physico-chemical) methods. Earthworms and their products (vermicompost) have emerged as a potential environmentally friendly option among biological remediation solutions. The purpose of this study was to assess the potential of the earthworm Eisenia fetida to remove heavy metals in SS suplemented soil. The vermiremediation process was performed at different SS soil treatments (0-200 kg/ha) using adult earthworms. As a result of vermiremediation, soil heavy metal concentrations were significantly reduced. Higher than 80 % vermiremediation efficiency was reached for a few heavy metals (Ni, Co, Mn), and the bioconcentration factors were as follows: Zn>Co>Cu>Ni>Mn>Cr. In addition, vermiremediation affected soil quality: soil pH was stabilized, organic matter mineralization quickened, K and Mg concentrations have slightly decreased, and the content of Ca and key nutrients (P, S) has increased. The greatest potential for vermiremediation was reached in SS soil treatments of 25-50 kg/ha. It is important to note that higher SS concentrations (? 100 kg/ha) in soil may limit this method’s use due to possible lethal effects on earthworms and growth retardation. Altogether, the study suggests that vermiremediation using Eisenia fetida might be a sustainable, successful and environmentally friendly management strategy for stabilizing SS amended soil, reducing toxic effects and converting it suitable for safe use in agriculture. |
