Municipal Solid Waste Incineration Bottom Ash Research Articles

Comparison of Digestion Methods for Analysis of Heavy Metals in MSWI Bottom Ash

This work aims to develop a proper digestion method for measurement of heavy metal content in municipal solid waste incineration (MSWI) bottom. Different digestion methods by HNO3, HNO3/HCl, HNO3/HCl/HClO4, HNO3/HCl/H2O2, HNO3/HClO4, HNO3/H2O2, were compared in digestion efficiency, and Cu, Pb, Zn and Cd were analyzed using atomic absorption spectrum (AAS). The method using mixed HNO3/HCl/HClO4 was recommended for digestion of MSWI slag for measurement of Cu, Pb, Zn, and the method of HNO3/H2O2 recommended for digestion for measurement of Cd.

Use of Municipal Solid Waste Incineration Bottom Ash in Adsorption of Heavy Metals

Bottom ash from municipal solid waste incineration (MSWI) has been previously suggested as an adsorbent for removing heavy metals from wastewater due to its high porosity and large surface area. In this study the adsorption characteristics of heavy metals were investigated using various particle sizes of MSWI bottom ash. The adsorption experiment was conducted using synthetic wastewater containing Cu, Zn, Pb and Cd as a function of residence time, initial pH, ash dosage and particle size, respectively. The adsorption rate increased with decreasing particle size and with increasing residence time. Through the above analysis, this work proved that bottom ash was effective in adsorbing the four heavy metals.

Utilization of municipal solid waste incineration ash in Portland cement clinker

Municipal solid waste incineration (MSWI) ash is used in part as raw materials for cement clinker production by taking advantage of the high contents of SiO2, Al2O3, and CaO. It is necessary for environmental reasons to establish a material utilization system for the incineration waste ash residue instead of disposing these ashes into landfill. The aim of this paper is to study the feasibility of replacing clinker raw materials by waste ash residue for cement clinker production. MSWI bottom ash and MSWI fly ash are the main types of ashes being evaluated. The ashes were mixed into raw mixture with different portions of ash residue to produce cement clinker in a laboratory furnace at approximately 1400°C. X-ray diffraction and X-ray florescence techniques were used to analyze the phase chemistry and chemical composition of clinkers in order to compare these ash-based clinkers with commercial Portland cement clinker.

Hydrothermal solidification of municipal solid waste incineration fly ash

Hydrothermal solidification of municipal solid waste incineration (MSWI) fly ash has been conducted under saturated steam pressure at 200 °C for up to 48 h with quartz addition. To enhance the strength of solidified specimens further, the raw fly ash was pre-treated by water-washing and mixed with NaOH solution (2 M) as reaction solvent. Experimental results showed that curing time and temperature had significant effects on strength development. Strength development was found to be mainly due to tobermorite formation, and addition of quartz and NaOH solution promoted tobermorite formation. The raw fly ash could also be used as an additive to solidify MSWI bottom ash, and with raw fly ash addition (10%) the flexural strength of solidified specimens reached more than 21 MPa, suggesting high potential to recycle 100% MSWI ash (e.g. as 10% fly ash + 90% bottom ash). Leaching tests were conducted to determine amounts of heavy metals dissolved from solidified specimens. The results showed that under the hydrothermal conditions of this study, leaching of heavy metals was very low. As such, the hydrothermal processing method might have high potential for recycling/reusing MSWI fly ash on a large scale.

Investigation of Cu leaching from municipal solid waste incinerator bottom ash with a comprehensive approach

Municipal solid waste incinerator (MSWI) bottom ash is often reused as a secondary construction material. This study used a comprehensive approach to characterize the leaching behavior of copper (Cu) from the MSWI bottom ash. The batch titration procedure was used to determine the acid neutralizing capacity and Cu leaching as a function of pH. The sequential extraction procedure (SEP) was adopted to analyze the speciation of Cu in the MSWI bottom ash. The metal speciation equilibrium model for surface and ground water (Visual MINTEQ) was used to evaluate the equilibrium of the leachates with the relative minerals, and to determine the speciation of the aqueous Cu in the leachates. Based on the multi-analysis of the results, Cu would be significantly released from the MSWI bottom ash when it is acidic. The Cu leaching pattern was not only affected by dissolved organic carbon, it was also limited by its speciation in the MSWI bottom ash. Furthermore, almost 100% of the aqueous Cu in the leachate was bound to organic matter in basic and neutral conditions, but mostly existed as Cu2+ in an acidic condition. These findings provide an important insight into predicting the leaching behavior of Cu from the MSWI bottom ash, as well as its impact on the environment.

Technical and environmental long-term properties of industrial residues – Summary of field and laboratory investigations

In Sweden, use of industrial residues is still hindered by concern for their long-term properties. A three-year research project was therefore initiated aiming to (1) identify the crucial processes of ageing related to the usefulness of residues in roads; (2) investigate the consequences of these processes for technical and environmental properties of the residues, and (3) propose a method for accelerated ageing to predict the long-term properties. This paper gives an overview of the project methodology, a summary of the test results and references to papers where further details are given. The project, running through 2006–2008, compared naturally aged samples of two residues used as sub-bases in existing asphalt paved roads with samples of fresh residues from producers’ piles. Steel slag of electric arc furnace (EAF) type and municipal solid waste incinerator (MSWI) bottom ash were chosen. The samples were thoroughly characterised in order to identify which ageing processes had been crucial. The results showed that: - Bottom ash from the pavement edge was more aged than bottom ash from the road centre. However, no difference in pH was found, instead the differences were caused by differences in water exposure. - Steel slag from the pavement edge showed traces of carbonation and leaching processes, whereas slag from the road centre was identical to fresh slag. - Water exposure to the subbase materials after ten years in an asphalt paved road was calculated to less than 0.1–0.5 litres per kg. - Ageing reactions in steel slag and MSWI bottom ash, ready for use, were too small to be verified by laboratory measurement of deformation properties under loaded conditions. An accelerated ageing test for steel slag was set up to achieve the carbonation (decrease in pH) and leaching that was observed in the pavement edge material. An accelerated ageing test for bottom ash was set up to achieve the pozzolan reactions that were observed in SEM analyses of in situ specimens. It is recommended to use uncrushed particles when properties of aged material are studied, in order to preserve the original particle surfaces.

Effect of weathering treatment on the fractionation and leaching behavior of copper in municipal solid waste incinerator bottom ash

This work describes the effect of weathering of fresh quenched municipal solid waste incinerator (MSWI) bottom ash on the fractionation and leaching behavior of Cu. A sequential extraction procedure was used to characterize the fractionation of Cu in the fresh and weathered MSWI bottom ash samples. It showed that the organic matter bound fraction of Cu decreased drastically from 69% to 37% during the weathering treatment, while the residual fraction, Fe–Mn oxides bound fraction, carbonate bound fraction and exchangeable fraction increased from 24% to 54%, 3% to 4%, 2% to 3% and 2% to 3%, respectively. Furthermore, two standard leaching procedures, synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP), were carried out on the fresh and weathered samples. The leaching of Cu was attenuated with the process of weathering treatment in the SPLP procedure, but was enhanced in the TCLP procedure. The results suggested that the weathering treatment could change the fractionation and leaching behavior of Cu in MSWI bottom ash. Further research is required to correlate weathering of ash and mobility of Cu.

Recovery of MSWI and soil washing residues as concrete aggregates

The aim of the present work was to study if municipal solid waste incinerator (MSWI) residues and aggregates derived from contaminated soil washing could be used as alternative aggregates for concrete production. Initially, chemical, physical and geometric characteristics (according to UNI EN 12620) of municipal solid waste incineration bottom ashes and some contaminated soils were evaluated; moreover, the pollutants release was evaluated by means of leaching tests. The results showed that the reuse of pre-treated MSWI bottom ash and washed soil is possible, either from technical or environmental point of view, while it is not possible for the raw wastes. Then, the natural aggregate was partially and totally replaced with these recycled aggregates for the production of concrete mixtures that were characterized by conventional mechanical and leaching tests. Good results were obtained using the same dosage of a high resistance cement (42.5R calcareous Portland cement instead of 32.5R); the concrete mixture containing 400 kg/m 3 of washed bottom ash and high resistance cement was classified as structural concrete (C25/30 class). Regarding the pollutants leaching, all concrete mixtures respected the limit values according to the Italian regulation.

Building Blocks Incorporating Waste Materials Bound with Bitumen

This paper described an investigation and evaluation which was carried out in the United Kingdom-UK, on the properties of masonry building block materials that incorporate waste materials, namely: steel slag, crushed glass, coal fly ash, rice husk ash (RHA), incinerator sewage sludge ash (ISSA), municipal solid waste incinerator bottom ash (MSWIBA) or shortened as IBA, bound with bitumen or asphalt, named as Bitublock. The binder used was 50 pen bitumen. The properties of the blocks evaluated were: compressive strength, density, porosity, initial rate of suction (IRS), creep, and volume stability. It was found that the Bitublock performance can be improved by optimizing porosity and curing regime. Compaction level of 2 MPa and curing regime of 200°C for 24 hours gave satisfactory bitublock performances that at least comparable to concrete block found in the United Kingdom (UK). The Volume stability (expansion) of the unit is affected by environment relative humidity.

Mechanical properties of incineration bottom ash: The influence of composite species

The mechanical properties, including strength, deformational behavior, and wetting softening phenomena of municipal solid waste incinerator (MSWI) bottom ash are one of the major concerns for reuse applications. However, owing to the complex constituents of municipal solid waste, the properties of MSWI bottom ash are often highly variable. A series of artificial specimens with controlled chemical components were tested in this study. The test results show that the artificial bottom ash possesses the following mechanical characteristics: (1) for the strength, the frictional angles of the bottom ash under dry and saturated conditions vary from 34.8° to 51.1° and 26.0° to 37.2°, respectively; (2) for the deformation, the shear stiffness increases with the normal stress arises and degrades upon increased shearing; (3) significant wetting degradation of the strength and stiffness were observed. The multi-variable regression analysis was conducted to evaluate the associated influence of the chemical components on the strength. Among the evaluated components, Fe 2O 3 and Al 2O 3 are key factors; an increase in either results in higher strength at both dry and saturated conditions. The results were used to propose empirical relationships for ϕ dry and ϕ sat , expressed in terms of Fe 2O 3 and Al 2O 3. Accordingly, a strength classification chart is proposed for engineering purposes.

Ten-year chemical evolution of leachate and municipal solid waste incineration bottom ash used in a test road site

The use of municipal solid waste incineration (MSWI) bottom ash for road and car-park construction is an appropriate solution to reduce their disposal and the consumption of natural materials. In addition to leaching tests, the environmental impact assessment of such a waste recycling scenario critically needs for reliable long-term field data. This paper addresses a 10-year pilot site where MSWI bottom ashes have been used as road aggregates in Northern France (oceanic temperate climate). The paper focuses on the long-term evolution of leachate chemistry and the mineralogical transformations of MSWI bottom ash over 10 years. Data interpretation is supported by geochemical modeling in terms of main pH-buffering processes. The leachate pH and concentrations in major elements (Ca, Na and Cl) as well as in Al and heavy metals (Cu, Pb and Zn) quickly drop during the first 2 years to asymptotically reach a set of minimum values over 10 years; similar to those of a reference road built with natural calcareous aggregates. SO 4 release makes exception with a slightly increasing trend over time. Carbonation induced by CO 2 inputs, which leads to the successive dissolution of portlandite, CSH and ettringite, is one of the main phenomenon responsible for the geochemical evolution of leachate. On the other hand, mineralogical observations and batch tests demonstrate a relative stability of the MSWI bottom ash inside the subbase layer. In particular, carbonation may be far to be completed and still in progress after 10 years. This is consistent with preferential rainwater flow and dilution at the road edges combined to diffusion inside the subbase layer.

Aerobic microbial activity in fresh and aged bottom ashes from municipal solid waste incineration (MSWI)

Although mostly mineral, municipal solid waste incineration (MSWI) bottom ashes also contain organic matter that may support heterogeneous microbial activities. The objective of the present study was to evaluate the potential influence of such activities on the physico-chemical properties of the waste with respect to the release of contaminants into water. Fresh and aged MSWI bottom ashes originating from the same incineration plant were studied. Respirometry assays were carried out under various experimental conditions, where the microbial flora was quantitatively and qualitatively analyzed before and after the incubations. The leaching behavior of the waste was studied before and after the incubations to determine the effects of microbial activities. Relatively high O 2 consumption and CO 2 production were observed during incubation, particularly with the fresh waste which contained more organic matter and was less carbonated than the aged one. Cell counts and DGGE molecular profiles indicated the presence of an abundant and diversified microbial biomass in both aged and fresh waste. Incubations resulted in a reduction of the dissolved fraction of organic carbon in the leaching tests and a modification of the leaching patterns of many metallic species (Al, Cr, Cu, Fe, Pb and Zn). This influence on the leaching behavior was particularly significant with the fresh waste. It was mostly explained by the pH decrease due to the carbonation of the bottom ash resulting from the CO 2 generated by the microbial respiration.

Content, mobility and transfer behavior of heavy metals in MSWI bottom ash in Zhejiang province, China

Municipal solid waste incinerator (MSWI) bottom ash samples were taken from six cities of Zhejiang province, where 1/4 incinerators of China were located. The samples were instrumentally analyzed to detect the content of heavy metals. Sequential extraction procedure (SEP) was adopted to characterize the mobility and environmental impact of heavy metals. And the transfer coefficients of heavy metals from the input MSW to the bottom ash during the incineration were also calculated. It showed that the average content of Zn, Mn, Cu, Pb and Cr in the bottom ash exceeded 300 mg/kg, which was much higher than that in the soils. SEP results showed that although the residue fraction was the primary fraction of the heavy metals in the bottom ash, there were still 1.84 mg of Cd, 86.21 mg of Cu, 83.46 mg of Pb and 939.46 mg of Zn in 1 kg bottom ash having the potential of leaching, which indicated a great threat to the surrounding environment. The result of coefficients calculation revealed that almost all the Cu, Cr, Mn and Ni in the input MSW were transferred to the bottom ash during the incineration. Bottom ash was also the main destination of Cd, Co, As, Mo, Pb and Zn though considerable amounts of those metals were transferred to the raw gas.

산업부산물을 이용한 친환경 연소재벽돌의 제조특성

The main objective of this study was to evaluate the effects on shape and size, compressive strength, water absorption and heavy metals leaching with various weight mixing ratios in waste ash brick products using waste recycling MSWI(Municipal Solid Waste Incinerator) bottom ash, steel slag and waste building material. The manufacturing processes for the waste ash brick consist of screening, mixing, conveyor transmission, compaction.forming, and curing steps of raw materials. The weight mixing ratios of steel slag around bottom ash were adjusted within the ranges of 10% to 30%. The reported results show that the width and thickness of the manufactured waste ash brick could be satisfied with <TEX>$90{\pm}2mm\;and\;57{\pm}2mm$</TEX>, respectively which are K.S. standards of products qualities. And in case of length, only 20-Ba50Ss30, 20-Ba60Wb20 and 20-Ba50Wb30 for the mixing ratios could be satisfied with <TEX>$190{\pm}2mm$</TEX> that is K.S. standards of products quality. The compressive strength and water absorption for 20-Ba50Ss30 and 20-Ba70Wb10 were over <TEX>$8N/mm^2$</TEX> and below 15% respectively that are K.S. standards of manufactured waste ash brick. The results of tests for the heavy metals leaching in the all manufactured waste ash bricks are also passed to the wastes management regulations. The cost analysis of 20-Ba50Ss30 is evaluated. The manufacturing cost is evaluated 34.3 won/brick with 8 hours and 20tons of raw material per day. Incinerators with problems in bottom ash disposal can therefore derive significant benefits from the application of waste ash brick production.

Environmental assessment of incinerator residue utilisation

Incineration ashes may be treated either as a waste to be dumped in landfill, or as a resource that is suitable for re-use. In order to choose the best management scenario, knowledge is needed on the potential environmental impact that may be expected, including not only local, but also regional and global impact. In this study, A life cycle assessment (LCA) based approach was outlined for environmental assessment of incinerator residue utilisation, in which leaching of trace elements as well as other emissions to air and water and the use of resources were regarded as constituting the potential environmental impact from the system studied. Case studies were performed for two selected ash types, bottom ash from municipal solid waste incineration (MSWI) and wood fly ash. The MSWI bottom ash was assumed to be suitable for road construction or as drainage material in landfill, whereas the wood fly ash was assumed to be suitable for road construction or as a nutrient resource to be recycled on forest land after biofuel harvesting. Different types of potential environmental impact predominated in the activities of the system and the use of natural resources and the trace element leaching were identified as being relatively important for the scenarios compared. The scenarios differed in use of resources and energy, whereas there is a potential for trace element leaching regardless of how the material is managed. Utilising MSWI bottom ash in road construction and recycling of wood ash on forest land saved more natural resources and energy than when these materials were managed according to the other scenarios investigated, including dumping in landfill.

Combined use of MSWI bottom ash and fly ash as aggregate in concrete formulation: Environmental and mechanical considerations

This paper reports the experimental results obtained after casting concrete formulated with different mix proportions of municipal solid waste incineration (MSWI) by-products, bottom ash (BA) and air pollution control fly ash (APCFA), as aggregates. Several tests were performed to determine the properties of the mixed proportions. Mechanical properties of the formulations, such as compressive strength, were also determined, and two different leaching tests were performed to study their environmental effects. Some suitable concrete formulations were obtained for the 95/5 and 90/10 BA/APCFA mix proportions. These formulations showed the highest compressive strength test results, above 15 MPa, and the lowest amount of released trace metals in reference to the leaching test. The leaching mechanisms involved in the release of trace metals for the best formulations were also studied, revealing that the washing-off process may play an important role. Given the experimental data it can be concluded that these concrete mix proportions are suitable for use as non-structural concrete.

Carbon speciation in municipal solid waste incinerator (MSWI) bottom ash in relation to facilitated metal leaching

The release of inorganic and organic contaminants from municipal solid waste incinerator (MSWI) bottom ash is controlled to a large extent by the release of dissolved organic carbon (DOC), and in particular by the reactive humic (HA) and fulvic acids (FA) subfractions of DOC. The properties of organic matter contributing to the release of DOC, HA and FA are, therefore, important for environmental risk assessment. In this study we have quantitatively measured the carbon speciation, and its relation with the leaching of Cu, in three fresh and carbonated MSWI bottom ash samples. Results show that up to only 25% of loss on ignition (LOI) consists of organic carbon (OC), while about 17% of OC in the three samples consists of HA and FA. Up to 50% of DOC in MSWI bottom ash leachates was identified as fulvic acid (FA). This value is substantially higher than previously estimated for these MSWI bottom ash samples and is consistent with the higher recovery of the new method that was applied. The results of this study imply that methods focusing on specific carbon fractions are more appropriate for assessment of environmentally relevant organic carbon species than the measurement of LOI.

Change of Mineral Phases in Carbonation Reaction of MSWI Bottom Ash

ABSTRACT Municipal solid waste incineration(MSWI) bottom ash consists of glassy materials, ceramics, ferrous materials mainly. Therefore, in some European countries, it is used as construction material. But, the bottom ash is more considered as a chemically reactive material that releases hazardous heavy metals. In order to manage the bottom ash, understanding of the carbonation process is necessary. Because their influence on carbonation reaction in bottom ash may has a significant effect on the leaching characteristics of contaminants such as heavy metals. To gain a proper appreciation of the carbonation role of mineral constituent in bottom ash, it is essential to understand the relationships between their morphology, composition and their influence on carbonation reaction. Therefore, we carried out the study on mineral constituent of bottom ash and their influence on carbonation reaction.

Uranium in Municipal Solid Waste Landfill Leachate

Landfill leachates and leachate sediments were investigated in order to survey the discharge of uranium (U) from municipal solid waste (MSW) landfills and municipal solid waste incinerator (MSWI) bottom ash landfills. Concentrations of U in the leachates were as high as or higher than concentrations of Cd, a metal more often discussed when considering the environmental effects of landfill leachate. However, the U concentrations in leachate were no greater than levels occurring naturally in water. The U concentrations in leachate sediments were also the same as or lower than those reported in lake sediments around the world. Size charge fractionation of U in freshly sampled leachate showed that the metal was present mainly as either non-labile dissolved complexes or free anions, which have intermediate to high mobility and eco-toxicity. This is in contrast to other heavy metals, such as Cd, which are generally particulate bound in leachate. However, based on all the results of the investigations, it was concluded that leaching of U is not of major concern in MSW and MSWI bottom ash landfills.

Monotonic aspects of the mechanical behaviour of bottom ash from municipal solid waste incineration and its potential use for road construction

Municipal solid waste incineration (MSWI) bottom ash is an atypical granular material because it may include industrial by-products that result from the incineration of domestic waste. The prospects for the beneficial use of this particular material mainly lie in the field of road construction, as a substitute for the traditional natural aggregates. However, its mechanical properties are still little known, particularly in term of stiffness and deformability, characteristics that are essential to the construction of a durable roadway. The purpose of this paper is to describe better the mechanical behaviour of this recycled material. In order to reach this objective, a large experimental campaign is presented. The first part of this paper presents and comments in detail on the results obtained from static monotonic tests. Oedometric and triaxial shear tests were performed on MSWI bottom ash both before and after treatment with a specific hydraulic binder. These tests allow specification of the mechanical characteristics of the MSWI bottom ash, such as the initial Young's modulus, Poisson's ratio, the compressibility index, the friction angle, and the contracting or dilating behaviour of the material. The results reveal a mechanical behaviour similar to that of initially dense standard materials (sands, unbound granular materials) and a dependence on the applied average pressure, characteristic of the mechanical behaviour of granular media. More laboratory data on other samples of MSWI bottom ash are required to ensure that this comparison is statistically valid.