Specification of the problem

Coal and mixed sulphide mining and beneficiation activities, in Russia, have resulted in the generation of hundreds of millions of tons of hazardous mine wastes and tailings containing high loads of sulphur bearing minerals, such as pyrite, arsenoryrite, chalcopyrite and sphalerite. These wastes have been (are) deposited, throughout the years, in huge stockpiles and dams, in the outskirts of major Russian cities. Due to the action of rain, oxygen and bacteria, the sulphidic compounds of the hazardous wastes are oxidised, solubilize heavy metlas, and produce acidic waters with extremely low pH and high concentration of toxic elements. These leachates migrate and severely contaminate major lakes, rivers, other vital water reservoirs and therefore contribute to widespread environmental and health damages. In addition, these hazardous wastes are considered highly toxic, with high bioavailable and phytotoxic fractions of heavy metals; so, under the action of the wind, fine particles with elevated concentrations of toxic elements are transported over long distances and contaminate large agricultural areas. In such cases, toxic elements can be taken up by plants and finally enter the food chain, with adverse effects on human health.

Pollution in these sites, in the vicinity of major Russian cities, is progressively expanding, because hazardous waste dumps are continuous sources of contamination. Acidic water generation is a perpetual process, which, if started cannot be halted, due to the oxidation of the sulphidic phases with direct and indirect physico-chemical mechanisms. Therefore, the environmental situation in these areas rapidly deteriorates, affecting the quality of soils, water reservoirs (such as lakes, rivers and groundwater) and finally human health.

Industrial objectives

The main objective of this project is the development of innovative, cost effective and environmentally acceptable technologies, which will be applied on an industrial (large) scale, in order to prevent: (a) acidic water generation from hazardous mining waste dumps and (b) aerial transfer of fine grained contaminated wastes. When preventive technologies cannot be applied, decontamination of the effluents will be attempted, in order to prevent migration of the toxic elements and minimize the adverse effects on major aquatic systems. In addition, the development of an integrated environmental management scheme, based on the outcome of a risk assessment analysis, will produce a novel methodology for the proper disposal of the hazardous mining wastes and the application of preventative and remedial technologies for the protection of soil and water quality. It will also provide useful data concerning life cycle assessment of mining operations, aiming at waste minimization and long term control of rehabilitated sites.

The technologies that will be examined involve:

1.  Decontamination of hazardous wastes by a) chemical leaching, to permanently remove the toxic metals, b) bacterial leaching, to permanently break down the sulphide lattice and subsequently remove and recover toxic elements and c) chemical stabilisation, involving in-situ or ex-situ addition of chemical compounds to the hazardous dumps, in order to immobilise the heavy metals, by transforming them to less soluble and chemically stable compounds.

2.  Removal of heavy metals from acidic mine waters and leachates produced from hazardous waste dumps, by a) application of chemical treatment b) use of reactive barriers and c) construction of artificial wetlands

3.  Prevent a) oxidation of the sulphidic phases in the waste dumps, be impeding influx of water (precipitation and surface water) and oxygen into the waste mass and b) aerial transfer of contaminated fine particles by the application of a composite cover.