Utilization of municipal solid waste incineration bottom ash in the temporary landfill capping

The suitability of municipal solid waste incineration bottom ash (MSWI BA) for a temporary landfill capping was studied in real scale lysimeter tests. The main target was to investigate the performance of a capillary barrier... [ view full abstract ]

The suitability of municipal solid waste incineration bottom ash (MSWI BA) for a temporary landfill capping was studied in real scale lysimeter tests. The main target was to investigate the performance of a capillary barrier system built from the two mineral fractions of the MSWI BA. A capillary barrier system would be used in a temporary landfill capping as an alternative liner system.

Four capping structures with a capillary barrier system were investigated in the lysimeter container. The cross area of the container was 12.3 m²  and the length of the slope was 5.25 m. The used inclination of the slope was 1:7 which is the theoretical minimum for the capillary barrier system based on the literature. The seeping water was collected through welded feedthrough pipes to the farmer tanks (1 m³). The irrigated and seeped water were weighted using fork-lift scale (precision 0,5 kg). Three different top soil materials were applied: first so called “Helsinki moraine”, i.e. surplus soil containing some waste particles, second compost, and third gritting sand (2/3) mixed with fine crushing aggregate (1/3).  Two different mineral fractions of the MSWI BA were used in the capillary barrier system: 0-4 mm in an upper capillary layer and 4-12 mm in a lower capillary block. The performance of the capping structures were investigated based on the amount of water seeping through the different material layers and structures.

Based on the real scale lysimeter tests, only maximum 2.2 % of irrigated water seeped out from the capillary layer thus, the drainage capacity of the capillary barrier system wasn’t effective. A capillary barrier system built from the MSWI BA needs further research. The performance of the low permeability top soil layers (“Helsinki moraine” and compost) and the drainage geocomposite proved to be very effective to decrease the seeping of water through the underlying structures. However, the material, that is clayey or contains a lot of organic soil, was proved to be not suitable for the top soil layer due to the puddling and particle erosion. Only maximum 1.6 % of the irrigated water seeped through all the structure layers. Other potential further research option is to study compacted 0-4 mm mineral fraction of the MSWI BA use as a liner system or part of it for example with a compacted mineral soil.