Objective
THE RESULTS OF THE PROPOSED RESEARCH ARE DATA TO BE USED IN GROUNDWATER QUALITY MODELS TO ASSESS THE IMPACT OF DIFFERENT OPTIONS FOR DISPOSAL AND UTILIZATION OF COMBUSTION RESIDUES.
THE PROPER EVALUATION OF THE MAGNITUDE OF WASTE PROBLEMS, RESULTING FROM ENERGY CONVECTION SYSTEMS, AND SOLUTIONS IN TERMS OF UTILIZATION OF COMBUSTION RESIDUES IS A SUBJECT OF INTEREST TO ECN. FOR OTHERS THE DATA GENERATED AS WELL AS ASSESSMENTS OF ENVIRONMENTAL IMPACT OF OPTIONS CHOOSEN ARE RELEVANT.
THE EXPECTED RESULTS WILL BE USED BY INSTITUTES AND ORGANIZATIONS DEALING WITH GROUND WATER QUALITY.
IT IS EXPECTED THAT IN PARTICULAR VALUABLE NEW INFORMATION WILL BE OBTAINED ON THE MOBILITY OF DIFFERENT POLLUTANTS IN COMBUSTION RESIDUES, THE PRODUCTS OF COMBUSTION RESIDUES AND THE SOIL SYSTEM UNDERLYING A GIVEN UTILIZATION OF THESE MATERIALS.
Research has been carried out into the leaching from and mobility of contaminants in combustion residues. Attention was given to the source term for release to the environment and to phenomena at waste soil interfaces. Radiotracer diffusion methods and leaching tests have been applied to study. The diffusion measurement procedure, has been modified and applied to the measurement of trace element diffusivities in coal fly ash, coal fly ash products, clay soil, peat and sandy soil. In all matrices, sodium or tritium have been measured as a reference to identify effects of porosity, pore structure and degree of saturation with water. The influence of speciation, cementation, contaminant concentration and degree of saturation on the effective diffusion coefficients of some selected trace contaminants have been measured in a combustion residues and in soil. Rather than a change in porosity or pore structure due to cementation, the decreased effective diffusion coefficient for molybdenum is explained by loss of pore water in the cementation reaction.
The diffusion measurement set up has been modified to be able to measure the behaviour of (trace) elements under low flow conditions. Data obtained by this diffusion measurement method were compared with those of other diffusivity measurements.
The study of interface effects at the waste soil boundary by combining 2 different materials in a diffusion tube and measuring the diffusion of a labelled component from one material into the other has yielded valuable information. The processes occurring at interfaces can be studied in detail now in the laboratory. Precipitation reactions at or close to the interface appear to be particularly important for the net transport into the environment, when the effective diffusion coefficients of contaminants in the adjoining materials differ. The behaviour of molybdenum at the waste soil interface has been characterized for combinations acidic, neutral and alkaline ash with clay, sand and peat, respectively. The use of a constant source term for groundwater transport has been shown to be invalid for many constituents.
THE OBJECTIVE IS TO DEVELOP IN A JOINT EFFORT WITH VKI, OPERATIONAL MATHEMATICAL DESCRIPTIONS FOR THE MOBILITY OF RELEASED POLLUTANTS, IN PARTICULAR ANIONIC SPECIES OF AS, SE, SB, MO, B, W AND V, FROM
- DEPOSITS OF COMBUSTION RESIDUES;
- PRODUCTS CONTAINING COMBUSTION RESIDUES AND;
- WASTE FROM THESE PRODUCTS,
IN THE UNSATURATED ZONE AND IN GROUNDWATER FOR A BETTER ASSESSMENT OF ENVIRONMENTAL IMPACT WITH SPECIAL REFERENCE TO LONG TERM EFFORTS.