Effect of Chemical and Thermal Treatment on the Geotechnical Properties of Dredged Sediment

Dredging of sediments is necessary in order to maintain maritime activities and for flood prevention. However the increased industrial activities are causing accumulation of pollutants in the sediments. The main contaminants are heavy metals and organic compounds. Because of the cost of storage, treatment and valorization can be economically sound. This study focuses on the technology to treat heavy metals from dredged sediments using phosphoric acid (H3PO4) (the Novosol® process developed by Solvay company) with a goal to stabilize heavy metals by capturing them in calcium phosphate matrix and to destroy organic matter by calcination at 650 oC. Several studies have been conducted in this field. The stabilized materials obtained have been used in civil engineering. However these studies have never assessed the effect of the composition of the phosphoric acid on the treatment. In this paper the effect of two types of phosphoric acids with various composition and origins were compared. The investigation focuses on the effect of the phosphoric acids on the environmental behavior of metals and on the geotechnical properties of the dredged sediment.