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Final Report Summary - RECOAL (Reintegration of coal ash disposal sites and mitigation of pollution in the West Balkan area)

The aim of the RECOAL project was to assess the actual risk associated with the abundant coal ash disposal sites in the West Balkan area and to develop and test innovative low-cost methods for remediation of coal ash deposit surfaces and treatment of effluent waters.

The initial project phase was devoted to risk assessment and socio-economic problem analysis. Low cost technologies were developed in bench scale experiments. Thereafter potentially feasible technical solutions were tested in the field. This included the application of amendments and cover soils to reduce transfer of toxic elements and installation of a passive aeration cascade and filter systems to reduce the pollutant load and pH of alkaline ash disposal leachate. Moreover, pollutant low-uptake crops and cultivars were identified for minimising the risk of food chain contamination.

The specific project objectives were the following:
- Providing the scientific and technological basis for safe re-integration of ash dump sites in the West Balkan area using a combination of agronomic, ecological, soil technological and socio-economic approaches.
- Providing solutions for the protection of the food chain using low-pollutant uptake varieties of local crops combined with soil cover and soil amendments.
- Providing low-cost solutions for dust reduction by integrating measures of landscaping (buffer strips, wind belts), crop selection and crop rotation / inter-cropping (to provide permanent vegetation cover). Results and the feasibility of their implementation was demonstrated on two field sites.
- Providing innovative low-cost solutions for reducing pollution of local rivers from dump site effluents, using novel soil filter - phytoextraction and rhizo-filtration / chemical fixation technologies.
- Developing these technology packages in partnership with end users (farmers, municipalities), problem holders (power plant companies), stakeholders and policy makers in the West Balkan area, as part of the socio-economic work of the project.
- Fostering collaboration among countries and various ethnic groups in the West Balkan area and mediating the dialogue between local inhabitants and municipalities as well as power plant companies.

The project was divided into five work packages (WPs 1-5).

Work package 1 - problem / risk assessment:

The involvement of local people in the project was a priority of RECOAL. Collaboration with Municipal authorities was essential as they held the key for the long-term sustainability of the recommendations of RECOAL. The Municipality was the most important potential end user of the guidelines or toolkit that the project produced.

The stakeholder analysis revealed the importance of ensuring the effective participation of local communities and the municipal authorities. However, major issues rose regarding the involvement of local communities. There was a need for a much better understanding of their perceptions of the pollution problems and potential solutions.

At two experimental sites previous remedial efforts included the covering of ash deposits with mineral soil to prevent spreading of ash particles via wind erosion. However, tilling, as part of uncontrolled farming on some sites, caused mixing of mineral soil and ashes thus exposing ashes again to wind erosion and potentially contaminating food and fodder crops. Additionally, potential risk could arise from large Mo uptake by alfalfa (Cu:Mo ratio 1.25) which could cause hypocuprosis in ruminants. Trace element concentrations in crops were expected to increase if tilling of the soil was continued. Therefore, soil tillage should be avoided particularly on plots where the soil cover was less than the ploughing depth (30 cm). Establishing a permanent grass cover instead of tilling farming would reduce both: exposure of ash on the surface and the risk of hypocuprosis. Wild plants growing on barren landfill sites accumulated considerable amounts of trace elements including As, B, Cr and Mo. Remarkably high B concentrations of up to 1120 mg kg-1 were detected in leaves of willows. Compared to freshly-disposed ash, aged Coal Combustion Residues (CCR) showed decreased pH, EC and water extractable element fractions with the exception of As. Reducing conditions in the lower layers of the ash body of an abandoned landfill enhanced As concentrations in landfill leachates. The discharge of untreated, alkaline and toxic ash transport water from the active disposal site posed a large additional environmental burden to local water resources and aquatic organisms.

Work package 2 - processes / technology development:

Different locally available materials were tested for their pollutant sorption and pH reduction capacity. The best performing materials were subsequently tested in field studies.

Soil materials that were available in the vicinity of the experimental site and could be obtained at low cost and minimal work input were characterised according to standard soil analytical procedures.

In addition, locally available materials expected to immobilise pollutants in the coal ash and to support a rapid revegetation were tested in batch experiments.

Generally, organic amendments like sewage sludge and mixtures thereof, and brewery waste had a mobilising effect on arsenic, presumably due to displacement by negatively charged dissolved organic carbon. In contrast, maybe the major problem element for re-vegetation of freshly disposed ash, tended to be immobilised by the organic amendments. Therefore a sewage-sludge compost was produced on site and tested on a field scale in WP 3.

Pot experiments showed, that even compost of limited quality, mixed into the ash with volume ratios of approx. 1,25% to 2,5% or higher significantly improved the fertility of the ash. Ash amended with compost showed high yields of Festuca rubra. In comparison to pure ash 3 to 6 times more biomass was produced by plants grown in ash / compost mixtures.

Grass grown in ash / compost mixtures appeared to be more vital compared to grass grown in pure ash. Moreover, grass grown in ash / compost mixtures developed more root biomass and even longer roots than grass grown in pure ash.

Microbial activity in compost-amended ash was increased at higher compost application rates.

However, high boron uptake was observed in the course of the experiment for grass grown in pure ash and ash amended with compost.

In summary, compost applied to ash was observed to significantly promote plant growth and to substantially enhance the fertility of initially infertile ashes.

A series of crop varieties was tested in a green house study. The aim was to identify the crops / varieties with the least transfer of pollutants into edible plant tissues. Plants were grown in ash with or without amendments.

Pollutants transfer was generally high in non-amended ash. In general, barley cultivars showed less toxicity symptoms and accumulated lower concentrations of pollutants into edible / aerial plant part than bean cultivars and the fodder crop lucerne.

Work package 3 - testing:

- The application of compost made of sewage sludge, saw dust and straw to enhance rapid revegetation was tested on a barren plot of the site Divkovici I.
- An experiment at coal ash disposal site Dreznik for testing the effect of soil covers of varied thickness that had been abandoned during the Bosnian war was partly reactivated for the RECOAL project. The results revealed that cover soils generally should provide a more fertile substratum than pure ash.
- Three approaches for testing passive treatment of alkaline waste waters were tested under field conditions. Their principles and efficiency had been tested before in bench scale experiments.

Wind barriers were an effective method to prevent the dispersion of dust from the disposal sites. The presence of hedges and wooded landscapes also would have high acceptance among local residents and citizens from Tuzla. The dominant species of trees growing in the areas surrounding the disposal sites were Willows, Poplars, Maple, Beech, Alder, Hazel, Hornbeam, Elder, Ash and Horse Chesnut. Using native species in shelterbelts would help establish a stable wind barrier and preserve / improve local ecosystems. Attending to their landscape characteristics, RECOAL recommended the use of Poplar and Hazel.

Work package 4 - decision tools:

This report introduced decision support tools for putting together a strategy for the remediation and reintegration of Coal Ash Disposal (CAD) sites. The tools were developed as part of the RECOAL research project. The tools and the framework were largely aimed for use in the Balkan countries. However, its principles and structured approach could be suitable and useful for many other regions and countries within and outside Europe.

Work package 5 - project management, dissemination of knowledge, handbook:

Communication and management activities occurred virtually on a daily basis. Detailed project plans and related time schedules for the reporting period, agendas for the consortium meetings provided an overview of coming tasks and facilitated planning and collaboration of partners. The dialog among partners from West Balkan and EU was stimulated through the joint project activities, and in particular, through the joint meetings and sampling campaigns. Links between the EU and West Balkan partners were established to make some steps towards integration of the West Balkan teams into the European research scene.

A stakeholder workshop which was held in Tuzla, was designed to include a 'Presentation Session' and 'Poster Exhibition' that would enable the RECOAL partners to introduce the project and present its main findings, and a 'Group Session' with the aim of enabling key stakeholders to express their views on specific remediation options.

The handbook served to promote and support the reintegration of coal ash disposal sites in the Western Balkan area and to mitigate environmental risks that could result from industrial coal ash disposal. It provided structured tools to guide the user through key issues relevant to rehabilitating coal ash disposal sites.

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