Development of a sediment washing technique for the decontamination of heavy metals from dredged sediments in the harbour area of Taranto.

Among the research activities of the Institute for Coastal Marine Environment - "UOS" Taranto, the study the anthropic impact on marine ecosystems and the development of innovative technologies for "environmental remediation" have taken particular significance in recent years. Attention has been paid to the ecological risk analysis for contaminated sites and sustainable management of dredged sediment from coastal areas. The latter issue is of great relevance for the development of harbour areas, especially in Italy. Concerning dredged and contaminated sediments, the easiest option is often the landfill disposal, even if the problem is considerably complicated in relation to the volumes to be managed and/or treated and the simultaneous presence of different types of pollutants. In order to reuse the dredged sediments both civil and industrial sector, in recent years the development of treatment technologies textitex situ has assumed considerable importance. Among these, the "sediment washing" appears very interesting for the removal of toxic heavy metals from dredged sediments. For this purpose research has been started aiming to developing a new method of washing with chelating solutions on samples of sediments in the harbour area of Taranto, it's a site remediation of national interest. Different chelating agents (ethylenediaminetetraacetic acid (EDTA), Ethylenediamine- N,N'-disuccinic acid (EDDS), citric acid) were used at different extraction times. The optimum removal time was found to be 48 h, both with EDTA 0.2 M and EDDS 0.2M. Citric acid was not very efficient for the contamination process. The results suggest that bioavailability and speciation of metals in sediments were the main factors affecting sediment washing. In particular, metal speciation, using sequential extraction technique, were determined before and after washing: this approach was useful to evaluate heavy metals mobility in treated and untreated sediments. The methodology developed could have important implications on industry, also in view of reusing treated material for different purposes (filling, cement production, etc.).