Characterisation of organic materials from incineration residues

Abstract: The organic material present in incineration residues has been examined. Water leachable organic material was characterised and classified into hydrophilic and hydrophobic acids, neutrals and bases. Changes of the organic material during weathering were followed. Levels of polycyclic aromatic hydrocarbons in residues from the incineration of municipal solid waste and biofuel in a heating-plant, as well as in a biofuel and papermill ash mixture were determined. The total amount of organic material was higher in fresh bottom ash than in aged ash after open-air storage. Concentrations of organic carbon in the aqueous extracts were similar, resulting in increasing percentage of leachable organic carbon in course of time. The largest fractions of organic carbon in aqueous extracts from fresh municipal solid waste incineration ash were classified as hydrophilic neutrals and bases. During weathering, the composition of water leachable organic carbon changed. In aqueous leachates from a four-year-old ash deposit, some 5070% of leachable organic carbon was classified as organic acids. Levels of PAHs in the ashes varied widely. In MSWI bottom ash and heating-plant fly ash the levels of PAHs were low, but the mixed biofuel and papermill ash contained PAH levels exceeding the Swedish generic guidelines for PAHs in soil. The amount of carcinogenic PAHs in weathered MSWI bottom ash was, in some cases, found to exceed the Swedish generic guidelines for sensitive land use. However, the results imply that the amount of PAHs in fresh and weathered bottom ash are similar, indicating that the PAHs are strongly bound to the ash and not released to the environment after deposition on e.g. an open-air landfill. In heating-plant fly ash, the levels of carcinogenic PAHs were related to the amount of sleepers in the fuel. The distributions of PAHs were similar in all ashes and were dominated by low molecular weight PAHs such as naphthalene and phenanthrene.