Slag Disposal Site Research Articles

Comparison of Different Radiological Risk Assessment Scenarios at a Coal Ash and Slag Disposal Site

Coal fly ash and slag waste residuals from coal combustion are an issue of importance as one of the possible sources of environmental contamination and exposure to NORM. This study compares the results of different radiological risk assessment scenarios targeting terrestrial biota at a legacy site in Croatia that contains large quantities of coal ash with an enhanced content of radionuclides originating from previous industrial activities. The ERICA assessment tool was used for a risk assessment, which included data from borehole samples with a maximum depth of 6 m and trees as the primary reference organisms. The results of the risk assessments from various depth ranges found the radiological risk to the reference organisms to be negligible, regardless of the depth range, since the screening dose rate of 10 µGyh−1 was not exceeded in any of the assessments. The risk assessment results from all depth ranges show higher total dose rate predictions when the tool’s default CR values are used, compared to the site-specific ones, which is in agreement with previous studies on the application of the ERICA tool. A comparison of results from different spatial radiological risk assessments showed that sample depth does not affect the estimated total dose rate to biota.

Contaminant release from massive copper metallurgical slags: Insights from long-term monolithic leaching tests

Compared to compliance leaching tests performed on granular materials, leaching experiments on monolithic slags are more suitable for predicting the contaminant release when large boulders or poured slag layers are submerged in water, a specific environmental scenario typical for many smelting sites. We conducted EN 15863 dynamic monolithic leaching tests on massive copper slags over a prolonged period of 168 d. The patterns of the major contaminant (Cu, Co) fluxes indicated an initial diffusion process followed by the dissolution of primary sulfides with the maximum cumulative releases attaining 75.6 mg/m2 Cu and 4.20 mg/m2 Co. A multi-method mineralogical investigation showed that lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) started to form on the slag surface already after 9 d of leaching and partly immobilized Cu (but not Co). Vanadium and other trace elements (Zn, Pb, Cd) were leached to a much lower extent, initially controlled by diffusion followed by depletion and/or sorption to Fe oxyhydroxides. The results of the long-term leaching of the monolithic slag provide new information about the key processes affecting the release of metal (loid) contaminants under specific submerged conditions and have implications for the environmental management of slag disposal sites and/or potential reuse of slags in civil engineering.

REMEDIATION OF COAL ASH AND SLAG DISPOSAL SITE: COMPARISON OF RADIOLOGICAL RISK ASSESSMENTS

Residuals from coal combustion are known as a potential source of radiation exposure, especially in cases where the coal used in the combustion is characterized by increased radioactivity, resulting in coal ash and slag with potentially high activity concentration of radionuclides. This paper presents the results of the radiological risk assessments based on the ERICA Tool approach, used to estimate dose rates to terrestrial biota in the proximity of a coal fired thermal power plant in Croatia. The study consists of three radiological risk assessments using environmental data on activity concentration (Bqkg-1) from samples collected prior to the remediation of the disposal site and samples after the remediation implementation was completed. The resulting total dose rate to biota derived using data prior to the remediation ranged from 3.28 μGyh-1 to 147.68 μGyh-1. Assessment results of total dose rate based on the data from the studied area after remediation ranged from 0.23 μGyh-1 to 18.06 μGyh-1. The results showed that after the remediation only the total dose rate for lichens and bryophytes slightly exceeded ERICA Tool conservative screening value of 10 μGyh-1, which implies that environmental risks in relation to exposure to the disposal site can be considered negligible. The study results confirm the applicability of the ERICA Tool for the assessment of potential radiological impact and the effective remediation implementation at the coal and ash slag disposal site.

Utilization of modified copper slag activated by Na2SO4 and CaO for unclassified lead/zinc mine tailings based cemented paste backfill

Serious heavy metals pollution was characterized in the lead/zinc mine tailings dam and surrounding soils, as well as copper slag disposal sites. This study investigates the efficacy of modified granulated copper slag (MGCS) as a partial replacement of ordinary Portland cement (OPC) for lead/zinc mine tailings-based cemented paste backfill (CPB) application using Na2SO4 (CSN) and CaO (CSC) as alkali-activated materials. The effect of different scenarios was ascertained by unconfined compressive strength (UCS). Also, the correlated microstructural evolution and mineralogical phase generation were obtained by scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and X-ray diffraction (XRD). The main findings proved that CSN was more effective in improving mechanical performance. Na2SO4 was found associated with C–S–H gel formation accompanied by a compact microstructure and better pore distribution with lower porosity. However, deposition of chloride compound was found in the surface layer of CSN samples, which could bring deterioration to the mechanical properties. Results above extend the knowledge of reusing MGCS as supplementary material to CPB, promoting the concept of a circular economy demand for both lead/zinc mine extraction and copper industries.

Assessment of the State of Soil’s Microbial Community in Condition of Intensive Influence of Pollutants

Abstract This paper presents the study of toxicological state of the soil. It shows ecological and microbiological properties of the soil mantle in the areas of technological environmental impact and evaluates changes in the number of soil microorganisms as a result of toxic contamination of urban soil at different distances from the Moscow loop highway, and also as a result of dumping aluminum foundry slag in Orel region. Soil-inhabiting invertebrates species composition was evaluated at different soil contamination conditions. It was proven that the state of microbiocenosis changes depending on the intensity and character of the anthropogenic impact. It was established that soil fermentation and microbiological activity changes depending on the value of the cumulative heavy metals’ build-up coefficient. Study of interelement ties between the heavy metals concerned showed that they too may have the same anthropogenic origin regardless of their sources of origin. Pollution index indicates medium to high level of soil contamination in explored urban territories where vehicle emission is the main source of pollution, and dangerously high contamination of light-gray soil in the small settlement impacted by a nearby slag disposal site.

Study on Safety and Stability Evaluation of Waste Disposal Field of a Hydropower Station Based on <i>In Situ</i> Monitoring

Reasonable site selection, blocking to meet design standards, interception and drainage and other protective measures are the basic conditions for not causing disaster in slag disposal site. A hydropower station is located in mountainous area, the amount of slag abandoned is large, the grade of slag disposal field is high, and the site selection is difficult. On the basis of in Situ deformation monitoring, the slope stability of slag disposal site is calculated by Swedish arc method through the analysis of the scale, grade, site selection, surrounding environment, cut and discharge, blocking and protection design standards of slag disposal site. Under normal and abnormal operating conditions, the slope stability of slag disposal site meets the requirements of the code, and the results of in Situ deformation monitoring verify the calculation results of slope stability of slag disposal site by Swedish circular arc method.

Environmental radiological risk assessment of a coal ash and slag disposal site with the use of the ERICA Tool

The aim of this study was to assess the environmental radiological risk of coal ash and slag to terrestrial wildlife. The research site used in this study was a disposal site of coal ash and slag with enhaced content of uranium decay chain radionuclides. With the use of the ERICA Tool, total dose rates to wildlife and risk of resultant radiobiological effects were estimated. As input data for the assessment, experimental activity concentrations of 238U, 226Ra and 210Pb in coal ash and slag and best estimates of activity concentrations for related daughter radionuclides and 235U decay chain were used. Where possible, the experimental data for activity concentrations of 238U, 226Ra and 210Pb in plants and related concentration ratios were used. Results were compared to background dose rates, also estimated by the Tool. The Tool's assessment data indicated internal exposure as the prevalent exposure pathway with 226Ra and 210Po as the main dose contributors. Also, the contribution of 235U decay chain to the total dose rate was not negligible since for some organisms it represented up to 11% of the total dose rate. The risk of an occurrence of radiobiological effects in plants on the coal ash and slag disposal site can be considered negligible since the estimated total dose rates were below the screening dose of 10 μGyh−1 and near the dose rates estimated for plants in the control area. However, the estimated dose rates for reference animals and Lichen & Bryophytes were above the screening dose rate for most organisms and on average 13 times higher than the estimated background dose rates. At the given dose rates, an occurrence of different radiobiological effects could not be excluded for animals in close contact with coal ash and slag such as earthworms and small burrowing mammals. A separate assessment performed on an example of reference plants showed that the use of activity concentrations in organisms as input data can result in an order of magnitude smaller estimates of dose rates in comparison to activity concentration in coal and ash as input data. Our study highlighted the need for experimental data in radiological risk assessments to mitigate the conservatism of the ERICA Tool and its tendency to overestimate dose rates.

Biotechnology for thermal power plants. A review of recent and perspective technologies

The article considers key Biotech trends for thermal power engineering, in particular in wastewater treatment, flue gas cleaning, remediation of ash and slag disposal sites and oil-contaminatedsoils. An overview of key technological solutions in these areas is provided. Special attention is paid to phototrophic microorganisms application for CO2 fixation. List of possible products that can be obtained from these microorganisms is given. The latest data about lipids (main component for biodiesel production) productivity from different strains in different conditions are presented. Also, other possible applications of phototrophic microorganisms in combination with carbon dioxide fixation (biological pre-treatment and biodesalination) are shown. Aquaporin based reverse osmosis membranes are discussed. It is shown that today the introduction of such technologies becomes economically feasible, especially in the case of flue gases from thermal power plants used for the cultivation of phototrophic microorganisms to further obtain a wide range of products including pharmaceutical substances, biofuels and animal feeds.

Options for managing alkaline steel slag leachate: A life cycle assessment

Management of steel slag (a major by-product of the steel industry) includes the treatment of highly alkaline leachate (pH > 11.5) from rainwater infiltration of slag deposits to prevent adverse impact upon surface or ground waters. This study aims to compare different treatment options for steel slag leachate through a life cycle assessment (LCA). Five options were compared: active treatment by acid dosing (A-H2SO4), active treatment by carbon dioxide dosing (A-CO2), active treatment by calcium chloride dosing (A-CaCl2), passive treatment by cascade and reedbeds with pumping (P-P), and passive treatment by cascade and reedbeds in a gravity-driven configuration (P-G). The functional unit was 1 m3 of treated leachate with pH < 9, considering 24 h and 365 days of operating, maintenance operations every year, and service life of 20 years. Inventory data were obtained from project designers, commercial suppliers, laboratory data and field tests. The environmental impacts were calculated in OpenLCA using the ELCD database and ILCD 2011 method, covering twelve impact categories. The A-CaCl2 option scored worse than all other treatments for all considered environmental impact categories. Regarding human toxicity, A-CaCl2 impact was 1260 times higher than the lowest impact option (A-CO2) for carcinogenics and 53 times higher for non-carcinogenics (A-H2SO4). For climate change, the lowest impact was calculated for P-G < P-P < A-H2SO4 < A-CO2 < A-CaCl2, while for particulate matter/respiratory inorganics, the options ranked as follows P-G < P-P < A-CO2 < A-H2SO4 < A-CaCl2. The major contributor to these impact categories was the Solvay process to produce CaCl2. Higher uncertainty was associated with the categories particulate matter formation, climate change and human toxicity, as they are driven by indirect emissions from electricity and chemicals production. Both passive treatment options had better environmental performance than the active treatment options. Potential design measures to enhance environmental performance of the treatments regarding metal removal and recovery are discussed and could inform operational management at active and legacy steel slag disposal sites.

Adverse health effects of ferronickel manufacturing factory on local residents: An interrupted time series analysis

The first ferronickel manufacturing factory of the Republic of Korea was opened in Gwangyang City on October, 23rd, 2008. There has been public concern regarding heavy metal dust blown from the factory and slag disposal site. Therefore, we evaluated the health impact of the ferronickel factory on Gwangyang City residents by using interrupted time series analysis. We analyzed the monthly incidence patterns of asthma, allergic rhinitis, and dermatitis in Gwangyang City residents from 2004 to 2014. Data were gathered from the National Health Insurance Service database which covers all the hospital use data of entire city residents. Seasonality adjusted quasi-Poisson regression model was used to evaluate whether the operation of the ferronickel factory was associated with the immediate changes in the monthly disease incidence patterns. We set a control region, Yeosu City, near Gwangyang City to ensure that the changes in the disease incidence were specific to Gwangyang City. We conducted sub-regional level analysis to evaluate whether the disease incidence patterns were affected by the distance from the ferronickel factory. The risk estimates after operation of the ferronickel factory showed an abrupt increase in the monthly incidence of unspecified dermatitis [RR (95% CI), 1.75 (1.17–2.60)] and vasomotor and allergic rhinitis [RR (95% CI), 1.23 (1.08–1.39)] in men, and pruritus [RR (95% CI), 1.95 (1.51–2.52)], unspecified dermatitis [RR (95% CI), 1.65 (1.04–2.60)], and vasomotor and allergic rhinitis [RR (95% CI), 1.17 (1.04–1.31)] in women. These findings were significant even after accounting for the changes of the corresponding disease incidence of the comparison city, Yeosu. The effects were greater in young children (aged 0–9) and sub-regions near the ferronickel factory. Our study suggests possible association between the operation of the ferronickel factory and an abrupt increase of pruritus, unspecific dermatitis, and vasomotor and allergic rhinitis in Gwangyang City residents.

Plant uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K from a coal ash and slag disposal site and control soil under field conditions: A preliminary study

The aim of this study was to investigate the uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K by plants that grow on a coal ash and slag disposal site known for its higher content of naturally occurring radionuclides. Plant species that were sampled are common for the Mediterranean flora and can be divided as follows: grasses & herbs, shrubs and trees. To compare the activity concentrations and the resultant concentration ratios of the disposal site with those in natural conditions, we used control data specific for the research area, obtained for plants growing on untreated natural soil. Radionuclide activity concentrations were determined by high resolution gamma-ray spectrometry. Media parameters (pH, electrical conductivity and organic matter content) were also analysed. We confirmed significantly higher activity concentrations of 238U, 235U, 226Ra and 210Pb in ash and slag compared to control soil. However, a significant increase in the radionuclide activity concentration in the disposal site's vegetation was observed only for 226Ra. On the contrary, a significantly smaller activity concentration of 40K in ash and slag had no impact on its activity concentration in plant samples. The calculated plant uptake of 238U, 235U, 226Ra and 210Pb is significantly smaller in comparison with the uptake at the control site, while it is vice versa for 40K. No significant difference was observed between the disposal site and the control site's plant uptake of 232Th. These results can be the foundation for further radioecological assessment of this disposal site but also, globally, they can contribute to a better understanding of nature and long-term management of such disposal sites.

Geotechnical Properties of Fresh and Aged Basic Oxygen Furnace Steel Slag

AbstractThe steelmaking industry in the United States generates 9–16 million metric tons of steel slag every year. The excess steel slag (∼15 to 40%) that is not reutilized is stockpiled in steel plants and eventually landfilled at slag disposal sites. Use of steel slag in civil engineering applications can help alleviate the steel slag disposal problem and help preserve natural resources. Understanding the in-service performance of steel slag is essential for its proper use as a geomaterial by the construction industry. In this paper, the results of a series of tests (grain-size analysis, X-ray diffraction, specific gravity, compaction, maximum and minimum dry unit weight, direct shear, consolidated-drained triaxial compression, and long-term swelling tests) performed on samples of both fresh and aged basic oxygen furnace (BOF) steel slag from a steel plant in Indiana are presented and analyzed. The test results indicated that both fresh and aged BOF steel slag exhibit superior strength and stiffness cha...

Pollution Level and Assessment of Chromium in Agricultural Soil around Chromate Plant

Based on the environmental standard and environmental quality risk assessment criteria for soil of China, the pollution level and assessment of chromium in agricultural soil samples around chromate plant were analyzed. The 176 agricultural soil samples were collected according to radial distribution method near chromium slag disposal site and a radius of 150m in 11 areas at 10cm interval from the surface layer to the underground 150cm vertically on each monitoring point. The results showed that the concentration of Cr (VI) and total chromium decreased with the increase of the chromium slag disposal site distance. The content of Cr (VI) in the soil near pile of chromium slag was significantly higher than the background value and the surface soil Cr (VI) content is up to 30.54 mg/kg that the pollution index was 5.7. The content of Cr (VI) decrease with increase of the soil depth. The total chromium pollution index in surface soil near Chromium slag heap is highest for 4.61. The Cr (VI) content in soil is less than the standard value proposed by Environmental quality risk assessment criteria for soil at manufacturing facilities.

Characterization of a Cd2+-Resistant Strain of Ochrobactrum sp. Isolated from Slag Disposal Site of an Iron and Steel Factory

A cadmium-resistant bacterium designated as CdSP9 was isolated from the slag disposal site of IISCO, Burnpur, West Bengal, India. The isolate was identified as Ochrobactrum sp. on the basis of 16S rDNA sequence-based molecular phylogenetic approach and phenotypic characteristics. It is a Gram negative, short rod (0.5-1.0 micro), aerobic bacterium, growing well in LB medium between temperatures 10-42 degrees C, pH 6.0-9.0, and between 2 and 6% NaCl. The most preferred nitrogen and carbon sources for the strain are L: -proline, L: -lysine and fructose, maltose, respectively. Superoxide toxicity minimization by increased level of SOD activity also occurs in this bacterium. The heavy metal accumulation efficiency as determined by atomic absorption spectroscopy was found to be 0.214 mg/g of the dry weight at late log phase. The accumulation efficiency was directly proportional to the optimum growth conditions.

Hydrogeochemistry of Alkaline Steel Slag Leachates in the UK

Drainage from steel slag disposal sites can be extremely alkaline and a source of pollution to surface and ground waters. Data is presented detailing the hydrogeochemistry of seven highly alkaline (pH > 10) steel slag surface discharges in the UK. While there is the consistent presence of Ca–OH type groundwater in all the discharges, there are clear disparities in hydrochemical facies within and between sites, reflecting native hydrochemistry, source material and hydrogeological setting. The longevity of the pollution problem from steel slag disposal sites is highlighted at one site where the water quality records date back three decades. The consistent presence of Al, B, Ba, Fe, Sr, V and occasional presence of Cr, Mo, Ni, Pb were found at concentrations typically below surface water quality standards in the leachates. Some of the monitored metals (Al, Fe, Ni, V) were found to be lost from solution downstream of emergence in calcite-dominated precipitates which rapidly form at all sites at rates up to 100 g m−2 day−1. The low concentrations of potentially problematic trace elements in both solution and the sediments are discussed with regard development of economically viable passive treatment wetlands for highly alkaline industrial discharges.

Use of 87Sr/86Sr and delta11B to identify slag-affected sediment in southern Lake Michigan.

Slag is a ubiquitous byproduct of the iron-smelting industry and influences geochemistry and water quality in adjacent geologic units, ground and surface water. Despite extensive slag deposition along the Indiana shoreline of Lake Michigan, definitive evidence that slag has affected lakebed sediments has not been established. Concerns for the protection of water and ecosystem resources in the Great Lakes motivated this study to determine if strontium and boron isotopes could be used to identify and delineate slag-affected bed sediment in Lake Michigan. Sixty-five samples of bed sediment were acquired from the southern lobe of Lake Michigan and analyzed for 87Sr/86Sr and deltat11B. Samples immediately offshore from Indiana steel mills and slag-disposal sites contained higher median 87Sr/86Sr values (0.70881) than shoreline sediments collected elsewhere in the basin (0.70847) and uniquely decreased with increasing distance from the shoreline. The highest delta11B values occurred in sediments from the Indiana shoreline (+12.9 to 16.4/1000) but were also elevated in sediments collected offshore from three Lake Michigan cities (+11.7 to 12.7/1000). Contoured isotope data indicated that 82-154 km2 of bed sediment along the Indiana shoreline had elevated 87Sr/86Sr and delta11B values relative to shoreline sediments elsewhere in southern Lake Michigan.

Mineral precipitation and dissolution at two slag-disposal sites in northwestern Indiana, USA

Slag is a ubiquitous byproduct of the iron- and steel-refining industries. In northwestern Indiana and northeastern Illinois, slag has been deposited over more than 52 km2 of land surface. Despite the widespread use of slag for fill and construction purposes, little is known about its chemical effects on the environment. Two slag-disposal sites were examined in northwestern Indiana where slag was deposited over the native glacial deposits. At a third site, where slag was not present, background conditions were defined. Samples were collected from cores and drill cuttings and described with scanning electron microscopy and electron microprobe analysis. Ground-water samples were collected and used to assess thermodynamic equilibria between authigenic minerals and existing conditions. Differences in the mineralogy at background and slag-affected sites were apparent. Calcite, dolomite, gypsum, iron oxides, and clay minerals were abundant in native sediments immediately beneath the slag. Mineral features indicated that these minerals precipitated rapidly from slag drainage and co-precipitated minor amounts of non-calcium metals and trace elements. Quartz fragments immediately beneath the slag showed extensive pitting that was not apparent in sediments from the background site, indicating chemical weathering by the hyperalkaline slag drainage. The environmental impacts of slag-related mineral precipitation include disruption of natural ground-water flow patterns and bed-sediment armoring in adjacent surface-water systems. Dissolution of native quartz by the hyperalkaline drainage may cause instability in structures situated over slag fill or in roadways comprised of slag aggregates.