DOI: http://dx.doi.org/10.1065/jss2001.11.031 - - -
Remediation techniques on contaminated sediments are generally much more limited than for most other solid waste materials, except for mine wastes. The widely diverse contamination sources in larger catchment areas usually produce a complex mixture of contaminants that is more difficult to treat than an industrial waste.
In the first two chapters, additional information will be presented on in-situ treatment methods, which were the central topic in the Spittelwasser Case Study (JSS – Journal of Soils and Sediments, Vol. 1, No. 3, pp. 181–187), and on the development of ecologically sound dredging and processing techniques, where practical applicability had to be demonstrated as part of an integrated remediation chain. In the latter respect, mechanical separation of less strongly contaminated fractions may be a useful step prior to the final storage of the residues (see chapter 2, Treatment of Strongly Contaminated Dredged Materials). For most sediments from maintenance dredging, there are more arguments in favor of disposal rather than treatment (see chapter 3, Subaqueous Storage and Capping).
Consideration about the comparative assessment of the two basic management options of in-situ capping and dredging followed by sub-aqueous disposal are discussed on a legislative, economic and technical-environmental basis. The concept of capping of contaminated sediments in-situ has been developed in the last two decades as an ecologically sound and economic alternative to more costly remediation techniques. The main characteristics are related to the passive character of this concept, which minimizes labor and process costs. Mechanisms of contaminant retention in sediment caps is discussed with special regard to the chemical isolation component. From this consideration, the development of the active barrier concept is derived that denotes the use of reactive additives in capping layers to chemically bind one or more contaminants specifically. |
