On the desalination of dredged sediments for beneficial use: case studies, CHALLENGES and best practices
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
Maria Barciela-Rial, Claudia Mc Leod and Wouter R.L. van der Star
Abstract
Large amounts of sand are used in infrastructure projects and industry. Sandy sediments are therefore becoming scarce while billions of cubic meters of fine cohesive sediments are dredged worldwide to maintain navigation channels. Consequently, more and more of these fines will have to be used in infrastructure development. However, compared to sand, dredged cohesive sediments are more complex to use because they consist of a heterogeneous mixture of water, fines, sand, organic matter and gas, amongst other components. Sediments from marine areas also contain salt, which influences the physical and (bio)chemical behavior of the mixture. A study on the desalination of dredged marine sediment for different cases with different beneficial use of sediment goals (agriculture, flood defense, ceramic industry) was carried out. This included a desk study and laboratory experiments. The results of the lab tests show that mixing with freshwater reduces the concentrations of ions. As expected, the reduction of bi- and trivalent ions (Ca2+, SO42-) is lower than monovalent ions (Na+, K+, Cl-). Monovalent ions such as sodium and chloride are released immediately when mixing, keeping the concentration stable during the rest of the experiment. However, ions with higher valence such as sulfate are released progressively during a longer period of time. To the best of our knowledge, the present work represents the first systematic study on the desalination of dredged marine sediment. This work aims to bring insights on the evolution of the properties of cohesive sediment after being mixed with fresh water, and on the points of attention, challenges and best practices.
Keywords: Desalination of dredged sediment, beneficial use, best practices, sediment composition