Projects / Programmes
In-situ remediation of polluted ground in the area of the Old Zinc-Works at Celje
| Code |
Science |
Field |
Subfield |
| 7.00.00 |
Interdisciplinary research |
|
|
| Code |
Science |
Field |
| P420 |
Natural sciences and mathematics |
Petrology, mineralogy, geochemistry |
| Code |
Science |
Field |
| 1.05 |
Natural Sciences |
Earth and related Environmental sciences |
Polluted soil, heavy metals, in-situ remediation, engineering fill, geochemical modelling, LCA, LCCA, guidelines
Researchers (17)
Organisations (4)
Abstract
The project proposal addresses remediation of the soil in the area of Old Zinc-Works at Celje, which is so severely contaminated with heavy metals (Cd, Pb, Zn, and As) that it has a status of a hazardous waste. This degraded area is the vicinity of the centre of the city, covering an area of approximately 30 hectares in size and is the site of the former zinc smelting and chemical industry. After the relocation of industrial activities to a location outside the city, this area was not remediated and have remained more than 40 years a source of pollution for urban environment, presenting a possible health threats to the environment and biota through emissions of hazardous substances into water and air. Since the soil has a status of hazardous waste, there are two possibilities according to the national legislation: either transport of the soil abroad to be disposed at a landfill for hazardous waste (which is practically unrealistic because of approximately 3 million tons of waste) or remediation of the soil and its conversion into a building material that will be built in back into the ground at the same location as a quality engineering fill.
The scientific part of the proposed project includes several research parts in which the following activities are planned: (a) characterization of different types of the soil depending on the type and amount of pollution and soil’s geomechanical and hydrological properties – this is important both from the standpoint of planned remediation as well as from the point of engineering fill, (b) preparation of a large number of formulations with a range of immobilization additives (iron nanoparticles, calcium fly ash, bentonite clay, zeolite tuff) and optimization in view of their quantity, type and combination, (c) detailed characterization of the most promising formulations (regarding the mechanism and the rate of the reaction), (d) applying of the selected formulations of remediated soils as an engineering fill and instrumentation of the fill for long-term monitoring as the test field, (e) study of the long-term effectiveness of the immobilization with a laboratory simulation using the column tests at different pH values and different regimes of wetting and drying on one hand, and monitoring the composition and transport of the aqueous leachates within of the remediated soil installed as a fill at the test fields on the other hand (geochemical modelling and theoretical speciation of heavy metals will be performed as part of activity in this section), (f) the calculation of life cycle analysis (LCA) and life cycle cost analysis (LCCA), both in comparison with a deposal of contaminated soil at the landfill for hazardous waste.
On the basis of the acquired knowledge and field validations of remediation procedures, the first national guidance for professional, holistic and sustainable approach for the remediation of the areas contaminated with heavy metals will be created, which will serve as a background for technically feasible remediation also in other similar contaminated areas.
Envisioned procedures for remediation and construction of the fill can be done with the existing standard construction equipment. In addition to that, all proposed immobilization additives are locally available materials, from natural sources or generated as industrial by-products (nanoparticles) or combustion residues (fly ash). These facts are vital in assessing the economic acceptability of the use of these procedures for long-term remediation practice in this field and increase the possibility that it will gradually be possible to remediate the whole area and return it to the city for urbanization and new activities.
Significance for science
The contamination of soil, especially with potentially toxic metals, is a globally widespread problem. Compared to the expensive transport of contaminated soil to a hazardous waste landfill site, in which case valuable resources are wasted because the excavation site has to be filled with some other material, the in-situ remediation of contaminated soil is the most sustainable and also the best economic choice. In order for this process to be successful, basic knowledge is needed about the mechanisms and processes of immobilization of potentially toxic metals, as well as about the latter's stability at the site selected for their installation, regardless of any unpredicted changes in the environment. Appropriate immobilization additives are needed for each specific application, and, if possible (in order to reduce the size of the carbon footprint and increase viability), these additives should be available in the local environment, where the remediation is to be carried out. It is equally important to develop a process for the correct installation and curing of the produced composites, where all the steps of this process are important (homogenization of the soil, mixing with the selected additives, the use of suitable compacting machines, and definition of the thickness of individual layers). Within the scope of the project the above-described knowledge and competences were obtained by means of selected laboratory and field investigations. At the laboratory level, characterization of the contaminated soil was first carried out, and then, on the basis of these results, effective immobilization additives were selected. The immobilization mechanisms of the toxic metals were defined on composites made from the contaminated soil and the selected additives. Mixing and placing procedures were optimized on a special test field, and appropriate monitoring was also performed in order to verify the effectiveness of the performed immobilization. The executed project has already had an important role in the achievement of an in-depth understanding of the processes in which many toxic metals can be bound, and also of their stability in the immobilization process taking place inside building composites. This knowledge is important for procedures which will be used in the future for the remediation of contaminated soils, and will encourage the development of reliable and long-term stable procedures. The acquisition and use of these skills in operational practice will ensure faster and more efficient remediation, and accelerate the remediation of brownfield sites. It can reasonably be expected that such newly acquired knowledge will be important not only for Slovenia, but also for other parts of the world where there are serious problems with contaminated soil. By means of comprehensive research, which is intended primarily for industry, the project has contributed to new knowledge in the fields of geology, chemistry, and construction, up to the international level. This is proved by an international patent which has been taken out on this subject (described as achievement 1 in point 7). In 2017 an international patent was applied for, with regard to the topic of water remediation (using zero-valent iron nanoparticles), which is partly related to the topic of the remediation of contaminated soils. Within the framework of the project, the young researcher Primož Oprčkal upgraded his knowledge in this field, and will defend his doctoral thesis on 26.3.2018: The topic of his PhD research is the remediation of contaminated water and soil, with the title “Innovative Approaches for the Sustainable Remediation of Contaminated Waters and Soils”.
Significance for the country
The research was performed in order to find out how, in Slovenia, to best approach the question of the in-situ remediation of soil polluted by toxic metals, i.e. what kind of remediation procedures could be used, and which locally available additives might be the most appropriate. Such an approach represents a shift from the established practice in which excavated contaminated soil is transported to other countries, or else ends up in "ad hoc created locations", which means that the problem has simply been moved from one location to another. The results of the scientifically based research will be of particular importance for the project co-financers. All three of them work in the construction industry, and are particularly involved in the search for more sustainable technologies and materials; in this field environmental pollution has already been identified not only as an important problem but also as a business opportunity. They have recognized that solutions for the remediation of contaminated soils can be optimized and integrated into their own work in the field of the recycling and use of various non-hazardous industrial and municipal waste. According to the Waste Directive the term "non-hazardous" includes waste that is inherently inert, as well as waste that should be deposited in municipal landfills. The project co-financers usually have to deal with waste of the second type, which means that its useful value in the construction industry depends on the success of the immobilization procedure. Based on knowledge and experience obtained in this project, they will be able to develop their own procedures and methods. The project will thus increase their competitiveness and offer them new business opportunities for the development of new products / technologies / business models with added value. Important aspects of these new opportunities include the possibility of the closing of material loops at the local level, and the creation of opportunities for cross-sectoral cooperation between builders and owners / owners of waste / owners of contaminated land. This is in line with the current EU and Slovenian strategies, which also require more sustainable management of resources (i.e. increased efficiency in the consumption of raw materials), and the reduction of greenhouse gas emissions. The wider professional public, too (i.e. construction companies, holders of industrial and municipal waste, designers, legislators and other decision makers) will be able to benefit by making use of the prepared Guideline and through further dissemination of the project results. Expected synergy in the field of land remediation and the remediation of industrial and municipal waste will bring positive environmental and economic effects. The project will also bring social benefits, and, with the gradual implementation of the practice developed in the project, the quality of life of the inhabitants of the Republic of Slovenia will increase due to a cleaner environment. Putting the research into practice: this was done in the manner that was the subject of the research in the project, on part of the site of the Old Zinc Works at Celje, where, in 2014/2015, approximately 13,500 m3 of contaminated soil was remediated. Paper ash from the firm Vipap Videm Krško was used for this purpose. This in-situ remediation method will also be used for contaminated soil, which was excavated in 2017 during the rehabilitation of the railway-line which runs through Celje. This work is expected to begin in the autumn of 2018, after the obtaining of a corresponding environmental permit. In the same way, contaminated soil will be rehabilitated on land with the parcel number Teharje 115, if the detailed research, which will begin shortly, confirms that the practically certain assumption that this contaminated soil has a negative impact on the environment.
Most important scientific results
Annual report
2014,
2015,
final report
Most important socioeconomically and culturally relevant results
Annual report
2014,
2015,
final report
