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ECN publication
Systematic leaching behaviour of worldwide MSWI bottom ashes in spite of their variability in content
Zomeren, A. van; Sloot, H.A. van der
Published by: Publication date:
ECN Environment & Energy Engineering 26-2-2014
ECN report number: Document type:
ECN-B--14-003 Book
Number of pages: Full text:
17 Download PDF  

Published in: Sustainable Landfilling, 366, 376, 978-88-6265-005-2, CISA Publisher, Italy.

Municipal Solid Waste Incineration (MSWI) bottom ash is used in several countries as a construction product. The percentage of the total annual production of ash used beneficially for construction purposes in different countries varies substantially (Chandler et al., 1997;CEWEP, 2010). The environmental properties of the material have been studied extensively in the last decade (Chandler et al., 1997; Dijkstra et al., 2002; Dijkstra et al., 2006b; Dijkstra et al., 2006a; Johnson et al., 1996; Meima et al., 1999; Meima and Comans, 1997; Rendek et al., 2006; Yan et al., 1999; Zevenbergen et al., 1994; Chen, 2007; Kalbe, 2007) The leaching behaviour of Municipal Solid Waste Incinerator bottom ash was already identified as rather systematic (van der Sloot et al., 1996). Dijkstra et al. (2006a; 2008) have shown that leaching tests (pH dependence test (CEN/TS 14429, 2006) and the percolation test (CEN/TS 14405, 2006)) are highly suitable to characterize MSWI bottom ash leaching behaviour. For a mechanistic interpretation of test results and their translation to field situations, knowledge is required on the geochemical and mass transfer processes that control the leaching of contaminants in a percolation regime. Reactive transport modeling will be a valuable instrument to identify and describe the dynamic leaching processes of constituents from a material (the “source term”) as well as their further transport in soil and groundwater. A key issue for the commercial use of MSWI bottom ash in construction is the type of testing and the frequency of testing required to meet regulatory criteria, such as the Dutch Soil Protection Act (2008). A hierarchy in testing is a very powerful means of providing the detailed knowledge, which it is needed for criteria development and product improvement, and the quick information, which is needed for regular quality control of the final product prior to delivery. There are developments in Europe in relation to the essential requirement number 3 on health and environment under the Construction Product Directive (1988). This work has just started in CEN/TC 351 with the development of the tools for national regulations to refer to. The aim of this study is to review current knowledge on leaching test methods and the data-interpretation of MSWI bottom ash test results. It will be shown that the leaching behaviour of MSWI bottom ash is rather systematic within a certain bandwidth and that the remaining variability of results can be explained by (the extent of) chemical processes leading to release. This work on MSWI bottom ash can be shown to be of relevance for the entire range of bottom ashes produced in one installation of relevance for ashes from different Dutch installations as well as bottom ashes produced in different countries. For this the database /expert system LeachXS provides unique capabilities (van der Sloot et al., 2003) allowing such comparison and data evaluation.

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