Abstract

The management of dredged material for beneficial use requires the assessment of all-possible strategies and available technologies to reduce the open sea dumping. The recoveries of sand of dredged material for beach nourishment harbour facilities, and for land improvement, are considered to be the most valuable activities for re-use of marine sediment.
  To this end, a pilot project was carried out in order to investigate the quality of separated sand from polluted dredging sediment. This project was conduced with a small sand separation plant where the sieved dredged material was introduced into a settling basin, allowing the progressive settling of coarse, heavy and medium particles. Two areas with different chemical and grain size composition of sediments were chosen in Livorno harbour as study site. The quality of the materials was estimated through sediment texture analyses, level of contaminants and ecotoxicological tests. The results of ecotoxicological analyses showed a high toxicity in the sediment sampled in situ and in the different grain size fractions separated through the pilot plant. Taking into account the contaminant distribution, a different behaviour was observed between the two different areas. In particular, in the less contaminated area the process of mechanical separation determined a reduction of the pollutants in the sand fraction more effective than in the more contaminated one. This might depend on the presence of particle aggregates, physically similar to the sandy fraction, but that could concentrate high amounts of contaminants.
  The results of these investigations evidence the necessity to develop further treatment processes addressed to a reduction of the toxicity case-by-case.