PROGNOSTIC MODEL OF SUBSURFACE CONTAMINATION CAUSED BY NEW EMBANKMENTS ON THE TERRITORY OF MARITSA EAST COAL MINING COMPLEX – CENTRAL SOUTHERN BULGARIA

One of the many environmental problems resulting from electricity generation in thermal power plants is the release of large amounts of solid wastes (coal combustion products). In the absence of effective eco–friendly disposal practices, this waste is accumulated in the form of coal ash embankments or in the excavated parts of the open–cast mines. The so constituted big landfills and surface impoundments emit leachate emissions containing a wide range of conventional pollutants among which, by definition, sulphate ions (SO4) dominate. Using the computer program VS2DI, a numerical model is developed of the conditions for mass transport of pollutants (using the example of SO4) from the designed new embankments for deposition of non–hazardous industrial solid waste from TPP in the area of the internal embankments of Troyanovo–North open–cast mine, part of the Maritsa East Coal Mining Complex. The scheme of convective–diffusion mass transport is employed, taking into account reversible elimination (sorption–desorption), mechanical dispersion and mixing. On the basis of the developed model, a long–term prognosis (100 years) is made for the extent and the degree of subsurface contamination from the new embankments. Based on the model solutions, the retention capacity of the geological foundation and the risk of groundwater pollution are assessed.