Characterisation of organic substances in waste materials under alkaline conditions

Sammanfattning: Organic substances are important constituents of different types of inorganic waste in that they can strongly influence the chemical behaviour and environmental properties of the waste materials. Two alkaline waste-material systems containing organic constituents were investigated: a cementitious radioactive waste repository and residues of incinerated municipal solid waste. Low- and intermediate-level radioactive waste to be deposited in a cementitious underground repository contains cellulose that will undergo slow alkaline degradation, and it is expected that the water-soluble species produced will influence the release of radionuclides to the environment. The rate and products of alkaline degradation of cellulose were investigated in a long-term (3-year) laboratory experiment. The main degradation products were identified and the kinetic relationships for cellulose degradation under the given conditions were determined. Degradation products were also examined regarding their behaviour in cementitious environments and their effects on radionuclide mobilisation. It has been established that the organics present in incineration residues of municipal solid waste can enhance the mobility of heavy metals, but little is known about the bulk composition of this organic matter, particularly the water-soluble fraction. A method for characterisation of this fraction was developed, and a number of individual compounds were identified. Based on the results and on data from the literature, a very rough estimate was made of the total chemical composition of organic matter in bottom ash.