Recycling contaminated marine sediments as filling materials by pilot scale stabilization/solidification with lime, organoclay and activated carbon

Abstract

Nowadays, stabilization/solidification (S/S) applied to the treatment of contaminated marine sediments (CMSs) represents a key technology for the production of new materials for civil engineering. Literature has shown the feasibility of CMSs recycling, although sediment needs pre-treatments for the removal of organic matter and to improve the mechanical properties of the product post S/S. In view of the full-scale applicability where it is essential to reduce any additional phase (i.e., pre-treatments), this study is aimed at demonstrating the technical feasibility of recycling CMSs as filling materials by S/S treatments with lime, organoclay and activated carbon. The original sediments are contaminated with heavy metals, PCBs, and PAHs, exceeding limits values prescribed by law. Different mixtures were tested on the STABSOL-P pilot scale plant. The absence of specific CMSs pre-treatments resulted in failure to comply with the 28-days leaching test only for copper; greater air curing with 56-days allowed it to be complied with for all the investigated metals. The organic contamination, while slowing down the process of chemical stabilization, allowed in any case to get a product environmentally compatible. The unconfined compression strength tests showed values (>28 kPa) that would allow potential CMSs recycling for environmental enhancement. The mass balance of the case study of the Mar Piccolo of Taranto (Southern Italy) showed potential recycling of marine sediments (the production of 974 kg filling materials per 1000 kg of dredged sediment) with a consequent missed disposal in landfills of 0.65 m3/1000 kg of sediment.