Predictions of leaching from municipal solid waste (MSW) and measures to improve leachate management at landfills

Sammanfattning: Landfill leachate from municipal solid waste (MSW) landfills is a long-term emission problem, which may last for several hundreds of years. The waste management resulting in this type of problem cannot be considered sustainable. This doctoral thesis focuses on the possibilities for changing leachate management strategies in order to enable a greater degree of sustainability. The first part of the study focuses on results from laboratory and field experiments and addresses the long-term behaviour of MSW leaching. Methodological considerations, qualitative differences between leachates and quantitative estimations are included. The second, applied, part of the study includes sampling at two different landfills in Sweden and focuses on evaluation of - the possibilities and limitations of separate collection of polluted waters within a landfill area and - the possibilities of extending the content of monitoring programmes without extending the analytical programme. The results of the first part show that predictions of leachate qualities should not be performed with small-scale shaking leaching tests. Landfill simulator reactors are more appropriate. The results also confirm that leachate poses a long-term problem and that nitrogen is likely associated with the longest lasting environmental concerns. The time required to reach concentration limit values depends largely on the actual landfill design. The period to reach concentration limits is more generally expressed in terms of liquid to solid ratios than time. The period may be shortened by enhanced stabilisation of MSW. This may be done by, e.g., an increased water addition to the waste, an increased recirculation and a decreased size of waste particles. The results further show that it would be beneficial to implement separate collection of different polluted waters within the landfill area, especially with respect to surface run-off waters and leachate, but potentially also with respect to different leachates. Such a separate collection would facilitate an effective pollutant-oriented treatment without the need to manage unnecessarily large quantities. The number of analyses within a leachate monitoring programme can, by means of multivariate data analysis (MVDA), be reduced without loss of crucial information about the excluded analyses. Alternatively, it may also be possible to retain the number of analyses, but extend the information to include additional substances, like specific organic compounds. In the latter case, the added substances need to be included in a reference set for model creation.