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ECN publication
Prediction of the long-term leaching behaviour of a sustainable landfill containing predominantly inorganic waste
Published by: Publication date:
ECN 1-10-2005
ECN report number: Document type:
ECN-RX--05-166 Conference Paper
Number of pages: Full text:
15 Download PDF  

Presented at: Sardinia 2005, Tenth International waste management and landfill symposium, Sardinia, Italy, 3-7 oktober 2005.

The predominantly inorganic waste landfill concept is part of a larger project on sustainable landfill concepts in the Netherlands. The project is aimed at creating biogeochemical equilibrium between a landfill and the environment within a period of 30 years, in order to reduce the long-term risk and the aftercare needs. It has already been reported that there is in general a very good agreement between the leaching behaviour of the constituted waste mix (analysed on laboratory and lysimeter scale) and the leachate as obtained from the full-scale pilot demonstration cell. However, deviations in the leaching behaviour of Cu, Fe and Mn have been found between experiments on laboratory-, lysimeter- and pilot scale. The different redox potentials lead to relatively large deviations in the emissions of Cu, Fe and Mn on the different test scales. It is found that the cumulative release of Cu is much lower in the pilot experiment compared to the other test types (lysimeter and column leaching tests) due to a low redox potential under field situations. Cu(II) is reduced to Cu(I). Moreover, the affinity of humic substances for metal complexation is possibly much lower for Cu(I) species and the formation of relatively insoluble copper sulphides may be a dominant process. Fe and Mn show a relatively high leaching in the pilot experiments, which is in line with the laboratory column test results but much higher than the lysimeter experiments. Fe is normally present as Fe(III) and can easily be reduced to more soluble Fe(II) species in a reducing environment. The leaching of Mn in the pilot experiments and the column experiments is higher than the results for the lysimeters. Under reducing conditions like in the pilot experiment and (to a lesser extent) the column test, the soluble Mn(II) species will be dominant. This species can easily be oxidised to Mn(IV) which forms solid oxides. Geochemical release modelling on column leaching test data showed that the model generally predicts the release of Cu, K, Pb and SO4-2 very well. This implies that the chemical processes leading to release are understood. The results indicate that preferential flow aspects are important for the long-term prediction of the release of mobile elements from a landfill. The model predicts the release quite well. This modeling approach is comprehensive in that it deals with all major, minor and trace elements simultaneously and partitioned between dissolved (free and DOC bound) and solid phases (minerals, Fe-oxide, Al-oxide and particulate organic matter). However, a few contaminants show deviations in concentration of over one order of magnitude and these deviations need to be sorted out in future work.

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