Jadwiga Szczepańska

III.7 – Coal combustion waste

Coal combustion residues are one of the most abundant high-volume waste materials. Their proportion in the total waste stream highly depends upon the role of coal in power production, and is, as a rule, the highest in coal producing countries. Coal-based power production results in generating a huge amount of coal combustion waste (CCW) worldwide. Coal statistics reflect on one hand, the range of CCW in the total waste stream and on the other hand, non-uniformity of the distribution of this waste in particular countries, producers, and the users of coal. The beneficial properties of CCW make it suitable for a wide array of commercially and technically proven applications. The traditional leading markets for CCW use are cement and concrete production, structural fills, road base and sub-base, and blasting grit/roofing granule. Traditional ways of CCW disposal are surface ponds (lagoons) or landfills. In dry compacted landfills, CCW are disposed pneumatically. For both disposal systems—that is, ponding and landfilling—a long-term environmental evaluation of disposed fly ash (FA) in relation to the actual field conditions is necessary because it has direct environmental and economic consequences.

III.6 – Mining waste

Mining waste is the high-volume material that originates from the processes of excavation, dressing, and further physical and chemical processing of a wide range of metalliferous and non-metalliferous minerals by opencast and deep shaft methods. It comprises overburden, run-of-mine rock, as well as discard, slurry and tailings from the preparation/beneficiation or extraction plants. The kind of mining waste and its share in the total waste stream in different countries highly depend on their natural resources, economic value of a mineral, and market demand, and therefore ranges from almost none to a predominant proportion. The major high-volume waste-generating mining activity in many countries worldwide is coal mining. Coal plays an integral role in the economy of many countries, and thus constitutes a substantial part of the global stream of mining waste. Petrographically, coal mining waste consists of argillaceous and arenaceous rocks, represented mainly by mudstone, siltstone, and sandstone with admixture of coal and coal shale. The properties of freshly wrought waste largely depend on the regional variability and stratigraphic position of mined coal seams. Mineralogical composition of the waste material is determined by the presence or dominance of the particular lithological types of carboniferous rocks, which is, in most cases, mudstone.

Chlorides in the Carboniferous rocks of the Upper Silesian coal basin: Environmental contamination and prognosis

Abstract The spoil discharged from coal mines in the Upper Silesian coal basin contains considerable amounts of readily soluble chloride salts which leach out causing deterioration of the quality of surface and underground waters in the vicinity of the spoil tips. The salinity of these Carboniferous rocks has been shown to be a result of the saturation of pore spaces with underground waters of variable salt content. This relation can be used to determine the chloride content of spoils based on the regional distribution of underground water salinity. Knowledge of the spatial variability of the chloride content of the Carboniferous rocks can be used to forecast the properties of deposited spoils and to neutralize their impact on the adjacent hydrogeological environment.

Occurrence and Mobilization Potential of Trace Elements from Disposed Coal Combustion Fly Ash

Despite many beneficial properties, high amounts of fly ash (FA) from coal-fired power plants have been disposed in landfills. These amounts are continuously growing in consequence of the limited possibility to utilize all generated FA due to the lack of market for it, or too high shipping/handling costs compared to the natural competing materials. Besides landfilling, the increasing utilization of FA as agricultural soil amendment that give an opportunity to dispose this material in a big scale also leads to its spreading on the vast land surface where it is exposed to the atmospheric conditions. To assess the effect of weathering processes on the mobilization potential of trace elements in disposed FA, the unique studies were carried out that comprised sampling FA along the vertical profile of 12 years’ old FA pond in the post-closure period, extracting pore solution from the material by a pressure method and direct analysis of its chemical composition using ICP-OES technique. Studied FA represented alkaline aluminum silicate material of a composition and trace element enrichment within the range typical for FA from the majority of other hard coal-fired power plants. The chemical composition of pore solutions along the three vertical profiles in the fly ash disposal pond in the post-closure period after 12 years’ operation was found to reflect both the altered water flow (vertical downward redistribution of ions) and the changed equilibria conditions. While the pore solution in FA in H6 profile reflects the Dissolution stage (II) (pH 7–10), in the looser FA profiles H-2 and H-3 it indicates alteration of buffering properties of the system that can be defined as Delayed Release (III) stage. The character of pore solutions along these profiles suggests that the major buffering mechanisms controlling pH after depletion of carbonates comprise reactions involving hydrolysis of aluminum ions from amorphous phase exposed to the direct contact with percolating water due to the devitrification of glaze, with further formation of the secondary minerals. These processes in simplified form can be described as reactions between dissolved silica, water, as well as kaolinite and gibbsite at the stage of their formation. This caused high non-linear release of trace elements from FA and significant qualitative/quantitative increase of its contamination potential with respect to the ground water and soils in adjacent area (decrease of pH to min. 4.3–4.5, and delayed extensive release of Zn, Fe, Mn, Mo, Cd, Cr, Be, B, Vin high concentrations). In conformity with pH-Eh-stability fields metals can be grouped according to the similar release-dissolution response to controlling parameters, e.g.: I: (Zn-Cd-W-Be); lI:(FeMn) (reverse pH-dependent increase). Several metals (mainly oxyanions with broad fields of aqueous species) show weak influence of pH-Eh parameters (Li, Mo, Se, Sr, B), while Al, Cu and V are immobilized at pH 4.3–5.0. The screening study proved (i) possibility of FA acidification and discontinuous non-linear time-delayed increase of its pollution potential to the hazardous level due to weathering transformations (ii) necessity of life-cycle screening/monitoring of FA disposal sites for trace element release as a function of controlling factors along the vertical profile of anthropogenic or natural vadose zone. The results suggest also caution in use of FA as acidic soils improver.

VI.6 - High-volume mining waste disposal

This chapter discusses a risk management approach to the contamination caused by high volume mining waste disposal in the current disposal strategies and practices with respect to coal mining waste in the Upper Silesia coal basin (USCB) in Poland. Mine waste management practices in Australia and the United States are also discussed. Mining waste disposal permanently brings about a contamination threat to the groundwater of unprotected aquifers and surface water in dumping sites all over the world. At the stage preceding the design and construction of a dump or earthworks, the reliable evaluation of pollution potential to ground- and surface-water from waste, as well as the prognosis of the life-cycle leaching behavior and of impact on the aquatic environment in the area of the prospective waste disposal should be the basis for the dump location permit, rejection, or acceptance of a material for civil engineering constructions and protective measures to be applied.

Use of neural networks for assessment of adverse impact duration of solid waste disposal facilities on the aquatic environment

Routine monitoring and long-term studies conducted in 19-years’ hydrologic cycle in the Upper Silesia Coal Basin (USCB), Poland, show extensive release to ground and surface waters of contaminant loads from mining waste. For simulation of the time-dependent changes of Acid Rock Drainage (ARD) generation expressed as sulfate formation due to oxidation of ferrous sulfides occurring in solid phase of mining waste, models of supervised neural networks were used. It was found that with use of such a model, the time span in which the concentration of a contaminant will reach the permissible level or the process of its release will terminate could be evaluated with a precision sufficient for practical purposes (the relative error did not exceed 1%). The results of simulation of temporal and spatial contaminant concentration changes will be utilized as a basis for assessment of an extent of the environmental deterioration dependent on the duration of a waste disposal in the site. These analyses enable to obtain reliable models describing time-dependent changes of water quality in the vicinity of long-term contamination sources, which seems to be their most essential merit The models allow also to evaluate the duration of the adverse impact of a facility on the aquatic environment and to reduce the expenses on the monitoring through the reduction of a number of samples and analyses.

Precision of selected trace elements in groundwater: examples from regional groundwater quality monitoring in the Upper Vistula River Basin (Poland)

Regional Groundwater Quality Monitoring (GQM) in the Upper Vistula River Basin (UVRB) is a pilot scale element of an Integrated Water Management System in SE Poland (about 50,000 km2). The system is currently in the implementation phase. The objectives of the regional GQM network are: (1) to provide data for quality control in regionally important groundwater basins, particularly Major Groundwater Basins (MGWB) in this area; (2) to establish the groundwater vulnerability to large scale diffuse sources of pollution; (3) to perform the prognosis and to identify trends of long time groundwater quality change; (4) to establish the extent of natural and anthropogenic processes impact on groundwater quality. During the sampling of the groundwater monitoring network the Quality Assurance/Quality Control (QA/QC) program for hydrogeochemical measurements was implemented in parallel. The QA/QC program included the collection (using the same equipment as for normal groundwater samples) and analysis (to the same extent as in the normal samples) of additional special samples. The duplicate samples taken from randomly selected GQM sites were used to assess the precision of hydrogeochemical measurements based upon the analysis of variance (ANOVA). The QA/QC program as applied to the GQM in the Upper Vistula River Basin is illustrated in this paper in the examples of two selected trace elements: fluoride (F) and zinc (Zn). Technical variance ((sigma) tech2) values calculated by means of the classical and robust ANOVA are lower than 20% for the discussed trace elements. This confirms the satisfactory precision of hydrogeochemical measurements.

Assessment of chemical quality of ground waters exemplified in Major Groundwater Basin 332

The chemical state of groundwater in the Major Groundwater Basin (MGWB) 332 was assessed on the grounds of hydrogeochemical monitoring conducted in 2001-2003 in the network that comprised 37 monitoring wells (points). On the basis of concentration data of organic and inorganic chemical constituents, the chemical quality of water in the monitoring wells was evaluated. Aggregated data were used for an assessment of the chemical state of the whole basin. The evaluation of the water quality in the monitoring wells was conducted in accordance with the Directive of the Minister of Environment (RMS, 2004) by the comparison of concentrations of analyzed chemical constituents with limit values in the quality classes I-V. In general, the water quality fulfilled the criteria of III class, occasionally of IV and V.class. Water chemical state in MGWB 332 was evaluated as good, following the criteria specified in the EU Water Framework Directive 2000/60/EC and the draft EU Directive on the protection of groundwater against pollution (COM 2003), based on the mean values of chemical indicators for the whole basin. The recommended method of the chemical state assessment on the basis of mean concentrations in all the monitoring points caused vanishing the zones of unsatisfactory quality (class IV) in the averaged backgrounds. In practice, this will result in desisting from any action aiming to improvement of water quality in these zones. The results of this study show the need of reporting chemical state of groundwater quality also in the specific monitoring points, and not just in the averaged hydrogeologic units or subunits.

IV.5 – Principles of vadose and saturated zones monitoring in solid waste sites exemplified in mining waste dumps

Waste disposal sites (landfills) can be classified as potential non-point small-area sources of aquatic environmental contamination, though the area occupied by such facilities can range from several tens of square meters to several hundred hectares. They may be formed either as waste dumps on the land surface, or onto the land as impoundments. The amount of atmospheric precipitation that percolates through the vadose zone depends upon the infiltration rate ( I) . At solid waste disposal facilities, particular attention should be paid to the conditions of contaminant migration in the anthropogenic vadose zone of a landfill and in the natural vadose zone beneath the landfill base. The concept behind developing vadose zone monitoring is to provide an early means to detect and, subsequently, intercept or remediate contaminants release from waste disposal facilities before they infiltrate into the saturated zone and degrade recoverable groundwater resources. By providing an early warning for taking instant remedial actions, the potential costs and the loss of recoverable groundwater resources can be greatly reduced.

Screening and characterization of pollution potential from solid industrial waste dumps

Solid industrial waste dumps, being an anthropogenic part of the vadose zone, are potential non-point sources of ground water contamination. The early warning provided from qualitative and quantitative information on contaminant migration within a dump is an essential element in monitoring and screening sites for hazardous waste deposition that prevents degradation of recoverable ground water resources and permits to avoid either false positive or false negative errors in evaluation and prediction of the extent of environmental hazard. Multilevel sampling of dump and vadose zone cross-sections in the defined points of known waste age and dump construction delivers direct information on vertical distribution of contaminants as a function of time, that is a resultant of a dump and vadose zone hydrogeology, as well as of the mechanism and dynamics of constituent release, interaction and biogeochemical transformation in pore solution. The current presentation describes a procedure for multilevel sampling, pore solution extraction and examination and provides data (vertical profiles of contaminants distribution from a selected landfill site) that exemplify necessity of dump/vadose zone multilevel sampling for correct assessment of contaminants migration rate, understanding processes and conditions affecting contaminant transport, and enhancement of remedial response measures.