Utilization of fly ash for stabilization/solidification of heavy metal contaminated soils (original) (raw)
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Sustainability
The aim of this work was to check the possibility of using a concrete matrix to immobilize contaminants from ash (fly and bottom) originating from the combustion of solid municipal waste. This work presents tests of ash from a Polish incineration plant. Nowadays, the management of ash poses a big problem with respect to the high concentration of contaminants that constitutes an environmental nuisance (heavy metals, chlorides, sulfates, etc.). The excessive leaching of contaminants disqualifies ash from being deposited in landfills for hazardous wastes. Bottom ash following the combustion of solid municipal waste mainly contains calcium (23.81%), chlorine (5.44%) and heavy metal (Σ 11.27 g/kg) compounds, while fly ash is characterized by a high content of chlorine (7.22%) and heavy metals (Σ 7.83 g/kg). In the next stage, two concrete mixtures were designed and prepared, containing 30% of ash from combustion of solid municipal waste. The most advantageous physicomechanical properties...
Municipal waste incineration is a common technology applied worldwide in order to recover the energy content from waste. The solid residues from waste incineration are generated in significant quantities which end mostly in landfill disposal. The major environmental concerns in relation to the short and long term impact of landfilling are connected with the risk of leaching and subsequent release of potentially harmful substances, particularly inorganic salts and metals/trace elements, into environment (soil, water, air). For fly ash and slag arisen from fired coal power plants the dense slurry technology was developed, in order to minimize the risk of the landfill disposal leaching. The final product of this technology is the ash rock formed by the pozzolanic activity of the fly ash. The present study relates to research and analyze of results accomplished on a small scale facility upon the encapsulation of the solid waste incineration residues into coal fly ash rock matrix, thus reducing the leaching risks and making the landfilling possible. Thus a novel technology is proposed that turns a hazardous material into a less harmful one. Remarks in reference to the main factors of influence are expressed as well.
Applied Sciences
This study presents an innovative stabilization method of fly ash derived from co-combustion of municipal solid waste and sewage sludge. Bottom ash, obtained from the same process, is used as a stabilizing agent. The stabilization method involved the use of two other components—flue gas desulfurization residues and coal fly ash. Leaching tests were performed on stabilized samples, aged in a laboratory at different times. The results reveal the reduction of the concentrations of heavy metals, particularly Zn and Pb about two orders of magnitude lower with respect to fly ash. The immobilization of heavy metals on the solid material mainly depends on three factors—the amount of used ash, the concentrations of Zn and Pb in as-received fly ash and the pH of the solution of the final materials. The inert powder, obtained after the stabilization, is a new eco-material, that is promising to be used as filler in new sustainable composite materials.
Thermal treatment of toxic metals of industrial hazardous wastes with fly ash and clay
Journal of Hazardous Materials, 2007
Waste generated from galvanizing and metal finishing processes is considered to be a hazardous due to the presence of toxic metals like Pb, Cu, Cr, Zn, etc. Thermal treatment of such types of wastes in the presence of clay and fly ash can immobilizes their toxic metals to a maximum level. After treatment solidified mass can be utilized in construction or disposed off through land fillings without susceptibility of re-mobilization of toxic metals. In the present investigation locally available clay and fly ash of particular thermal power plant were used as additives for thermal treatment of both of the wastes in their different proportions at 850, 900 and 950 • C. Observed results indicated that heating temperature to be a key factor in the immobilization of toxic metals of the waste. It was noticed that the leachability of metals of the waste reduces to a negligible level after heating at 950 • C. Thermally treated solidified specimen of 10% waste and remaining clay have shown comparatively a higher compressive strength than clay fired bricks used in building construction. Though, thermally heated specimens made of galvanizing waste have shown much better strength than specimen made of metal finishing waste. The lechability of toxic metals like Cr, Cu, Pb and Zn became far below from their regulatory threshold after heating at 950 • C. Addition of fly ash did not show any improvement either in engineering property or in leachability of metals from the solidified mass. X-ray diffraction (XRD) analysis of the solidified product confirmed the presence of mixed phases of oxides of metals.
Assessing fly ash treatment: Remediation and stabilization of heavy metals
Journal of Environmental Management, 2010
Fly ashes from Municipal Solid Waste (MSW), straw (ST) and co-combustion of wood (CW) are here analyzed with the intent of reusing them. Two techniques are assessed, a remediation technique and a solidification/stabilization one. The removal of heavy metals from fly ashes through the electrodialytic process (EDR) has been tried out before. The goal of removing heavy metals has always been the reuse of fly ash, for instance in agricultural fields (BEK). The best removal rates are here summarized and some new results have been added. MSW fly ashes are still too hazardous after treatment to even consider application to the soil. ST ash is the only residue that gets concentrations low enough to be reused, but its fertilizing value might be questioned. An alternative reuse for the three ashes is here preliminary tested, the combination of fly ash with mortar. Fly ashes have been substituted by cement fraction or aggregate fraction. Surprisingly, better compressive strengths were obtained by replacing the aggregate fraction. CW ashes presented promising results for the substitution of aggregate in mortar and possibly in concrete.
Fuel, 2009
Coal fired electric power plants produce large volumes of fly ash and other coal combustion by-products (CCBs) every year. Although almost 50% of the fly ash produced in the US is recycled for beneficial use, most of the ash material is disposed in dry landfills and ash lagoon impoundments. Fly ash may contain hazardous leachable trace elements such as As, B, Cr, Mo, Ni, Se, Sr and V which have a negative impact on the environment due to potential leaching by acid rain and groundwater with time. Many of the older CCB disposal facilities are unlined and unmonitored and as a result the EPA is currently developing national standards for monitoring CCB disposal sites. The cost to the US electric power industry could exceed one billion dollars if existing and closed CCB disposal facilities come under regulation. Thus simple, low-cost and effective in situ chemical treatment techniques are needed to stabilize hazardous leachable trace elements in the coal combustion by-product (CCB) materials. This paper reports the results of experiments designed to chemically treat fly ash with ferrous sulfate solutions to immobilize hazardous leachable trace elements after disposal.
Archives of Civil Engineering
The growing number of municipal sewage treatment plants in Poland raises the problem of managing more and more sludge. The thermal treatment of municipal sewage sludge (TTMSS), which significantly reduces the volume of waste, results in an increase in the concentration of heavy metals in the fly ashes – the final products of the process. The search for methods of utilization of fly ash from TTMSS resulted in attempts to use it in hardening slurries widely used in hydro-engineering. Due to the nature of the application of this material in the cut-off walls (exposure to groundwater flow) one of the key issues is the degree of heavy metal immobilization. The paper attempted to determine the degree of leaching of selected heavy metals from the hardened hardening slurry, composed of fly ash from TTMSS. For this purpose, the eluates were prepared from samples, after various periods of curing, using a dynamic short-term method called “Batch test”. The liquid used for leaching was: distille...
A public property site, situated on an alluvial terrace of the Idice Stream (Emilia Romagna Region-Italy) was contaminated by a layer of waste, constituted by vitrified fly ashes and ceramic materials produced by an incinerator of municipal solid waste. The waste had high contents of heavy metals which exceeded the Italian legal concentration limits for Cd, Cu, Pb and Zn (D. Lgs. 152/06, all. 5, tab.1). The in-situ remediation of the area was possible. In this study, alternative materials than the Portland cement were tested for the environmental restoration and the further naturalization of the area. Leaching tests were carried out treating the ashes with different concentrations of hydrated lime (CaOH 2) and also with lime at 20% concentration and smectic marlstone. At the end of the leaching test, most of the heavy metals in the waste were immobilized in the waste by the lime/marlstone treatment.
Journal of Environmental Management, 2019
This paper proposes, for the first time, the use of sewage sludge ash (SSA), obtained by sludge combustion for the stabilization of fly ashes containing heavy metals as Pb and Zn. In particular, the proposed method aims to take advantage of valuable raw materials present in SSA, such as phosphate, silica, and alumina. The stabilization has been explained by the synergic phosphate, carbonation, and pozzolanic reactions together with the Friedel's salt formation. This method to sewage sludge management allows the complete recovery of valuable raw materials otherwise destinated for lanfill. This is virtuous example of the use of waste materials for de-pollution processes.
In this study, the efficiency of metals immobilization in sludge using pozzolanic materials fly ash and cement clinker dust (CCD) was investigated. Also, estimation of the optimum binder to waste ratio was determined. Different leaching tests such as the standard European (EN) 12457-2 leaching tests; the toxicity characteristic leaching procedure; and the multiple extraction procedure test were used to evaluate the efficiency of metals stabilization in sludge matrix, and they showed that the availability of metals leaching (Cd, Cu, Cr, Pb, Ni, Zn) from the stabilized sludge were lower than the permissible limit set by National and International regulations for hazardous waste management. Examination of the solidified sample for its compressive strength after curing for 28 days yielded a value of 1.55 and 4.57MPa for fly ash, and CCD which indicates that the treated sludge was well solidified and safe to be used in a wide variety of applications, for instance as a raw material for pavement blocks.