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Title:
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Prediction of the long-term leaching behaviour of a landfill containing predominantly inorganic waste
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Author(s):
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Published by:
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Publication date:
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ECN
Environment & Energy Engineering
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26-2-2014
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ECN report number:
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Document type:
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ECN-B--14-001
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Book
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Number of pages:
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Full text:
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25
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Download PDF
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Published in: Sustainable landfilling, 168, 186, 978-88-6265-005-2, CISA Publisher, Italy.
Abstract:
Although more waste materials are recycled or re-used nowadays, landfilling of waste materials is
still necessary in the future. The necessary everlasting aftercare of landfills raises concern. In the Netherlands, a Sustainable Landfill Foundation was set up in order to stimulate the development of new landfill technologies to minimize impact and thus reduce or eliminate the need for long-termaftercare. A five-year research program was started in order to develop and evaluate four sustainable landfill techniques (predominantly inorganic waste, organic waste, bioreactor and stabilised waste). The complete results of the project can be found in (Mathlener et al., 2006; van Zomeren and van der Sloot, 2006). The project aims at creating a iogeochemical equilibrium between a landfill and the environment within a period of 30 years, in order to educe the long-term risk and the aftercare needs. This can be accomplished by constructing a landfill that has chemical properties that will minimize leaching of contaminants (e.g. neutral pH, slightly reduced conditions, low organic matter content and relatively low salt loads).
Waste acceptance criteria such as specified in the EU landfill directive (1999) are based on test results from individual waste materials. However, it is unclear whether these results have any significance with regard to the final behaviour and emissions of a complete landfill. In earlier work (van der Sloot et al., 2001) laboratory tests were performed with relatively
small additions (up to 10%) of contaminated (or alkaline) waste materials to a stable (neutral pH, low organic carbon content) waste material (mix of sludge, soil remediation sludge and construction and demolition waste). We have shown that relatively small additions (up to 10%) of contaminated waste materials do not significantly disturb the leaching behaviour of the total waste mix. Key controlling factors for this predominantly inorganic waste disposal are controls on the individual waste dissolved organic carbon levels, mobile inorganic (e.g. Chloride and sulphate) and water-soluble organic contaminant levels. The long-term leaching behaviour of a landfill is strongly affected by the macro-chemistry, which is currently largely ignored in monitoring of percolate water. At the start of the project additional parameters have been identified that needed to be measured to enable chemical speciation modelling in order to understand the chemical processes in the landfill leading to a release of contaminants. A major challenge is to develop means to predict the long-term leachate quality based on geochemical reactive transport modelling taking into account the geochemistry as well as preferential flow aspects, which are occurring in landfills. The anticipated outcome is a disposal practice through waste acceptance that will reduce the contaminant emissions to acceptable levels on the long-term. Predic- tion of the long-term leaching behaviour of a landfill is particularly relevant for judging the need for aftercare. In this study, the results from column leaching tests are described by geochemical reactive transport modelling. This approach will enable
understanding of release processes under field conditions. Furthermore, preferential flow aspects will be addressed in the paper by comparison of the cumulative release of mobile species in lysimeter and field situations with the laboratory characterisation of the mixed waste entering the landfill. This gives an indication of the extent of preferential flow in the landfill compartment. This work provides a means of gaining more understanding and subsequently more control over the long-term release of inorganic contaminants and identification of possible long-term processes that can disturb the biogeochemical equilibrium of the landfill.
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