An evaluation of technologies for the heavy metal remediation of dredged sediments

Sediments dewatering is frequently necessary after dredging to remediate an d treat contaminants. Methods include draining of the water in lagoons with or without coagulants and flocculants, or using presses or centrifuges. Tr eatment methods are similar to those used for soil and include pretreatment , physical separation, thermal processes, biological decontamination, stabi lization/solidification and washing. However, compared to soil treatment, f ew remediation techniques have been commercially used for sediments. In thi s paper, a review of the methods that have been used and an evaluation of d eveloped and developing technologies is made. Sequential extraction techniq ue can be a useful tool for determining metal speciation before and after w ashing. Solidification/stabilization techniques are successful but signific ant monitoring is required, since the solidification process can be reversi ble. In addition, the presence of organics can reduce treatment efficiency. Vitrification is applicable for sediments but expensive. Only if a useful glass product can be sold will this process be economically viable. Thermal processes are only applicable for removal of volatile metals, such as merc ury and costs are high. Biological processes are under development and have the potential to be low cost. Since few low cost metal treatment processes for sediments are available, there exists significant demand for further d evelopment. Pretreatment may be one of the methods that can reduce costs by reducing the volumes of sediments that need to be treated. (C) 2001 Elsevi er Science B.V. All rights reserved.