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

Abstract

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°C. 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.

Performance of dredged sediments based controlled low-strength material

“…Dredging of sediments is a critical operation to maintain and improve the global and national water navigation [1], recreation, and defense systems [2]. Additionally, this operation is of great significance for flood prevention by reducing sea level [3], and coastal protection [4]. The materials excavated from waterbodies including waterways and harbors through dredging activities are recognized as dredged sediments (DS).…”

“…According to the United States Army Corps of Engineers [7], the average annual quantity of material removed from waterways and channels in the United States is approximately 152 million m 3 (212 million yd 3 ) during fiscal years 2008-2012. In many countries, dredged sediments are considered as waste material.…”

“…In most of the countries, only about 10% of dredged materials were reused, and 90% were either dumped into the sea or used for land reclamation [5,8,9]. [10], USACE dredge 152 million m 3 (200 million yd 3 ) of DS per year nationwide to maintain channels' navigation. Approximately, 38 million m 3 (50 million yd 3 ) DS are beneficially reused and 116 million m 3 (150 million yd 3 ) provide opportunity [10]).…”

“…[10], USACE dredge 152 million m 3 (200 million yd 3 ) of DS per year nationwide to maintain channels' navigation. Approximately, 38 million m 3 (50 million yd 3 ) DS are beneficially reused and 116 million m 3 (150 million yd 3 ) provide opportunity [10]). This 116 million m 3 (150 million yd 3 ) DS are enough for covering 1 m (1.1 yard) of approximately 10,918 soccer fields.…”

“…Approximately, 38 million m 3 (50 million yd 3 ) DS are beneficially reused and 116 million m 3 (150 million yd 3 ) provide opportunity [10]). This 116 million m 3 (150 million yd 3 ) DS are enough for covering 1 m (1.1 yard) of approximately 10,918 soccer fields. Some of the beneficial applications of dredged material are for beach nourishment, topsoil creation/enhancement, land creation/enhancement, habitat restoration and construction materials [11].…”