Gas permeability and retention study on Ämmässuo temporary landfill cover structures made with municipal solid waste incineration bottom ash

Abstract

This thesis focused on the gas permeability and retention study of the temporary landfill test cover structures made with Municipal Solid Waste Incineration Bottom Ash (MSWI BA). This study was done for Helsinki Region Environmental Services Authority to incorporate MSWI BA in the impermeable layer of the landfill cover structure. Accordingly, gas permeability studies were done in the Ämmässuo landfill on two different landfill test cover structures made with MSWI BA. Literature review was done for acquiring the knowledge on landfill cover construction, gas flow mechanism and the factors affecting the gas emission through the landfill cover structures. Impermeable layer of one of the test structures was made with 0-5mm MSWI BA and the other structures was made with 0-2mm MSWI BA and 3% polymer modified sodium bentonite. There was a considerable difference in the measured gas emission above the impermeable layer between these two test structures. This research study also explored the factors affecting the gas emissions through the impermeable layer of the landfill test structures. In addition to the gas permeability study of the two different landfill test cover structures, an experimental study was done on the MSWI BA-clay mixture to use it as an improved construction material for the impermeable layer of the landfill cover structure.

From the analysis on the gas measurements of the two test cover structures, it was revealed, the test structure that made with MSWI BA (0-2mm) and 3% polymer modified sodium bentonite was more effective in reducing the landfill gas emission than the other one. Experimental study results on MSWI BA-clay mixtures exhibited that the requirements of impermeable layer could not be completely satisfied with mixtures used for the tests. Outcome from the gas permeability study on the temporary landfill test cover structures and the experimental study on MSWI BA-clay mixture aided the Ämmässuo landfill in constructing the 2018 - temporary test landfill cover structure.