Desalination of dredged sediments for beneficial use: a case of study for raising agricultural peatlands

Purpose

Sediments from marine areas contain salt, limiting beneficial use possibilities. This study investigates the impact of rinsing with fresh water on ion concentration and organic matter (OM) content in marine sediments, and how salinity hinders water release under induction.

Methods

In a lab simulation, marine sediment was mixed with fresh water (1:6 volume ratio) for 5 min at 285 rpm using a HOBART planet N-50 Mixer. An adapted Thermogravimetric Analysis (TGA) procedure determined the OM content and the temperature at which all water was released.

Results

Mixing sediment with fresh water reduced ion concentrations. Monovalent ions like sodium and chloride were released immediately, while higher valence ions like sulfate and phosphate were released gradually. Rinsing with fresh water also reduced OM content. A second mix with the salty supernatant water did not further reduce salinity or OM.

Conclusion

Determining OM content in salty sediments requires continuous mass loss monitoring to identify the temperature at which all water is removed. For agricultural reuse, maintaining nutrient levels and OM while reducing salt content to prevent groundwater salinization is crucial. Supernatant water should be removed promptly after rinsing to halt nutrient removal. The results of this study contribute to beneficial reuse of dredged sediment.