Dewatering and remediation of dredged sediments under varying heavy metal contamination types and levels using electrokinetic geosynthetics-assisted vacuum preloading combined with electroosmosis

Electrokinetic geosynthetics-assisted vacuum preloading combined with electroosmosis (VPE) has been demonstrated to be effective for dredged sediment improvement. However, existing studies have mainly focused on dewatering, leaving the coupled mechanisms of dewatering and remediation in dredged sediments insufficiently understood. In this study, dredged sediments contaminated with Cu, Zn and Cu-Zn at two contamination levels were treated using VPE to investigate their dewatering and remediation behaviours. The results showed that higher initial Cu or Zn concentrations resulted in greater drainage volumes. The final drainage volume increased by 7.5% as Cu concentration increased from 50 to 800 mg/kg, and by 32% as Zn concentration increased from 200 to 2000 mg/kg. Compared with dredged sediments contaminated with Cu or Zn alone, those co-contaminated with Cu and Zn exhibited further enhanced dewatering performance. As initial contamination levels increased, the proportion of initial Cu inventory removed decreased from 28% to 10%, despite an increase in the absolute amount of Cu removed, whereas both the proportion and absolute amount of Zn removed increased, with the former increasing from 18% to 33%. At the same initial Cu concentration, Cu removal was enhanced in co-contaminated dredged sediments, whereas the presence of Cu did not promote Zn removal.