A pilot project was carried out to investigate the possibility of recovering sand from polluted dredging sediments and to evaluate its quality. This project was conduced with a small separation plant where the sieved dredged material was introduced first into a settling basin, allowing the progressive sedimentation of coarse, heavy and medium particles, and then in a hydrocyclone. Two areas with different chemical and grain size sediment composition were chosen in Livorno Port (NW Italy). The quality of the materials was estimated through analyses of sediment grain size, level of contaminants and bioassays on marine species (Vibrio fischeri, Corophium orientale and Paracentrotus lividus). Taking into account the contaminant distribution, different behaviors were observed between the two considered areas. In particular, the process of sand separation worked best in the less contaminated dredging sediment. This might depend on the presence of particle aggregates, physically similar to the sandy fraction, which could concentrate high amounts of contaminants. The results of bioassays provided a positive toxic response both in the two types of dredging sediment and in the resulting grain size fractions after the remediation process; tests carried out on elutriate accounted for a lower toxicity than those on bulk sediment. This suggests the presence of mixtures of hydrophobic contaminants associated with the solid phase. The results of these investigations demonstrate the necessity to develop further treatment processes to reduce the contamination and the toxicity in the sandy fractions separated from dredging sediments, in order to make them suitable for reuse.

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