Municipal Solid Waste Bottom Ash Research Articles

Use of Municipal Solid Waste Bottom Ashes in Rubberized Asphalt Mixtures

Abstract The increasing need of environment protection and preservation has been stimulating road agencies to progressively adopt sustainable technologies for the design, construction, and maintenance of their assets, with the consequent increasing use of recycled materials, industrial by-products, and wastes. In such a context, the experimental investigation presented in this paper moved from the idea of synergistically combining the use of bottom ashes originating from incineration of municipal solid waste (MSW) and crumb rubber from end-of-life tires. The performance-related properties of rubberized asphalt mixtures containing MSW bottom ashes in partial substitution of natural aggregates were evaluated by means of laboratory tests focused on the determination of workability, viscoelastic characteristics, anti-rutting potential, and resistance to crack propagation. Tests were carried out by considering an ash-amended rubberized asphalt mixture and, for comparison purposes, a standard gap-graded rubberized mixture (GGRM). Obtained results indicate that the rubberized mixture containing bottom ashes exhibited lower workability (16 % decrease in k parameter), reduced stiffness (decrease of dynamic modulus at 20°C of approximately 40 % and 60 % at 0.1 Hz and 10 Hz, respectively), and decreased anti-rutting potential (17 % decrease in flow number values) with respect to the standard GGRM. Conversely, the addition of bottom ashes was found to provide beneficial effects in terms of resistance to crack propagation (with fracture toughness values five times larger than those of the reference mixture). These outcomes suggest that the use of MSW bottom ashes must be carefully considered because environmental benefits may be counterbalanced by lower performance.

MSWIBA Formation and Geopolymerisation to Meet the United Nations Sustainable Development Goals (SDGs) and Climate Mitigation

Sustainable Development Goals (SDGs) constitute an action plan for the environment and people. One of the main goals is to limit the increase in global average temperature to 2 °C and aim for a stop at 1.5 °C. The goals of the circular economy (CE) are in line with the SDGs. In the waste management chain, the last CE element is a recovery in the municipal solid waste incineration plant (MSWIP). However, during recovery, municipal solid waste bottom ash (MSWIBA) is created (in about 30% of the bunch). The development of MSWIBA in the construction industry is a possibility of closing the cycle. This article shows the MSWIBA formation process, alkali pre-treatment of MSWIBA, and its geopolymerisation. Studies have determined the mechanical properties of geopolymer with MSWIBA and leachability from crushed and from monolith geopolymer. Alkali pre-treatment improves MSWIBA mechanical properties and upgrades immobilisation. Moreover, geopolymerisation is a better solution than concreting, because of the lack or low consumption of high-emission and energy-intensive cement. A SWOT analysis was carried out for the proposed solution.

Utilization of Different Grain Size of Municipal Solid Waste Bottom Ash in High-Performance Mortars

Globalization is bringing increased industrialization and municipal solid waste (MSW). This is a major concern in heavily populated areas. In order to reduce MSW generation, incineration is commonly used, resulting in two types of ashes: bottom and fly ash. Bottom ash is gathered at the incineration bed and is larger in mass than fly ash. To test the qualities of high-performance mortar, MSW-BA in three sizes (fine, medium, and coarse) was replaced with sand at three replacement levels of 10%, 20%, and 30%. The high-performance mortar integrating MSW-BA was tested for hardened density, mechanical properties such as compressive and flexural strength, resistance to NaOH solution, and heavy metal leaching. The substitution level of MSW-BA increased the hardened density of the mortar mixes. The volume change and residual strength of the mortar mixes were measured following exposure to the NaOH solution. Fine-particle mortar mixes shrank whereas medium- and coarse-particle mortar mixes expanded. The largest loss in flexural and compressive strength was recorded when 20% of sand was replaced with a fine fraction of MSW-BA. Heavy metals including cadmium and copper were not leached from MSW-BA combinations of any size. The minuscule amounts of lead and zinc discovered were well below acceptable limits. The present study illustrates the MSW-BA can be utilized as a substitute for sand in the development of high-performance mortar.

Incinerated municipal solid waste bottom ash bricks: A sustainable and cost-efficient building material

Incineration of Municipal solid waste leads to the generation of bottom ash and fly ash. The applications of fly ash are many, but the bottom ash is usually being disposed of directly to the landfills. The study seeks the application of municipal solid waste incinerated bottom ash in the manufacturing of bricks. Since bottom, ash has a high amount of silica, but due to high porosity and less unit weight compared to clay, the direct use of bottom ash is not feasible for brick production. Cement stabilizes the inorganic compounds present in ash and provides the required compressive strength. A series of compressive strength, efflorescence, pH, water absorption, and Ultrasonic pulse velocity tests were performed on eight different mix proportions. OPC 43 grade cement was used to replace 6, 8, 10, 12, 14, 16, 18 and 20% of incinerated bottom ash content by mass. These lightweight bricks fulfill the criteria of minimum water absorption even with 6% cement content, minimum compressive strength, and brick with 20% cement lie under the second-class brick, and the efflorescence for all bricks was under the required limits. The pH value varied from 11.44 at 6% cement content to 12.19 at 20% cement content, and the maximum value of ultrasonic pulse velocity obtained at 20% cement content was 2.74 km/s. A final cost analysis of these bricks was done with the conventional ones, which confirms that these bricks are equally efficient for the construction industry. The applications of these bricks were less but not limited to a specific use.

STATIC AND CYCLIC PROPERTIES OF MUNICIPAL SOLID BOTTOM ASH IN VIETNAM

: In this study, direct shear tests and cyclic triaxial tests were conducted to investigate the effectiveness of using municipal solid waste bottom ash (MSWIBA) material as fill material or base/sub-base in Vietnam. A square of large – scale (300 x 300 x 140 mm) and a small scale (60 mm in diameter) direct shear test were carried out on MSWIBA samples to study the effect of specimen size on shear strength of the samples. The results show that the MSWIBA sample at R95 has a very high CBR value of 115%, which is much higher than the CBR value of crushed stone for subgrade applications. The cohesion and friction angle in the case of R95 are higher than those in the case of R90. The value of cohesion and friction angle in the large direct shear test are significantly higher than those obtained in the small direct shear test. The shear strength of MSWIBA is like natural sand. The resilient modulus decreased with the increase of deviator stress in the case of R90 sample and increased with the increase of deviator stress in the case of R95. The numerical method results also show that MSWIBA material can be used as construction material such as roadbed and foundation layers.

Recent advances and applications of municipal solid wastes bottom and fly ashes: Insights into sustainable management and conservation of resources

Waste destruction through incineration has widely become an acceptable and popular choice globally. Despite being regarded as a sustainable option, if not operated and managed properly, it can be one of the least environmentally preferred options. It is agreed that the waste from municipal solid waste (MSW) can be considered a renewable energy resource due to its potential of being converted from “waste” into useful products and energy. This review for the first time incorporates both municipal solid waste bottom ash (MSW-BA) and municipal solid waste fly ash (MSW-FA); and discusses their physicochemical characterizations, leaching mechanisms, and pre-treatment methods. Additionally, it incorporates, discusses, and critically reviews the recent advances and applications of MSW-BA and MSW-FA, and explore the potential of utilizing ashes as a sustainable option by conserving natural resources.

Application of geopolymers synthesized from incinerated municipal solid waste ashes for the removal of cationic dye from water.

In this study, municipal solid waste bottom ash (MSW-BA) and fly ash (MSW-FA) were used as a source of aluminosilicate to prepare geopolymer (GEO) adsorbents (GEO-MSWBA and GEO-MSWFA) for the removal of methylene blue (MB) from water. The effects of temperature, pH, and initial concentration on the MB adsorption onto GEO-MSWBA and GEO-MSWFA were evaluated. The adsorption isotherms parameters and thermodynamics were also determined. Detailed physical and chemical characterizations of the prepared adsorbents were carried out to further understand their impact on MB adsorption. The results from the scanning electron microscopy revealed a uniform granule-sphere like structure on both prepared geopolymers, which would facilitate the MB adsorption onto the adsorbents. The X-ray diffraction allowed observation of the microstructural transformations that occur after the alkaline activation. The surface areas of the GEO-MSWBA and the GEO-MSWFA were recorded as 32.78 m2/g and 4.5 m2/g, respectively. From the Fourier transform infrared, a stretching vibration of the aluminosilicate tetrahedral was observed, which indicated the success of geopolymerization. The prepared geopolymers showed a high capability of MB adsorption from an aqueous solution. The adsorption process was best suited and explained using the Langmuir isotherm model with a maximum adsorption capacity of 666.7 mg/g for the GEO-MSWBA (at 25°C) and 769.2 mg/g for the GEO-MSWFA (at 35°C). The positive value of the enthalpy (ΔHo) for the GEO-MSWBA suggested the reaction favored endothermic reaction while the negative value of entropy (ΔSo) indicated a solid/liquid random interaction. On the other hand, the negative ΔHo value for the GEO-MSWFA indicated the reaction followed an exothermic reaction causing energy to be released, the positive ΔSo value indicated a good affinity at the solid-liquid surface. The overall negative value for Gibbs free energy (ΔGo) for both adsorbents suggested the adsorption was spontaneous and feasible. It was also inferred that n- π interaction, direct and indirect hydrogen bond, and electrostatic interaction between the MB and the prepared geopolymers facilitated the adsorption process. The current study shows that the GEO-MSWBA and the GEO-MSWFA have a great potential of removing MB as a cationic dye from water without performing any sort of laborious pretreatments.

Potential Use of Incineration Bottom Ash in Construction: Evaluation of the Environmental Impact

Knowledge of the long-term leaching behavior of potentially harmful substances is crucial for the assessment of the environmental compatibility of reusing municipal solid-waste incineration bottom ash (MSWI BA) in construction, i.e., as a road base layer. BA fractions obtained from wet-processing aiming at the improvement of environmental quality were used to investigate the mobility of relevant substances. Eluates from laboratory-scaled leaching procedures (column percolation and lysimeters) were analyzed to learn about the long-term release of substances. Unsaturated conditions and artificial rainwater (AR) were used in the lysimeter tests to simulate field conditions. In addition, batch test eluates were generated at usual liquid-to-solid ratios (L/S) for compliance testing purposes. A variety of cations and anions was measured in the eluates. The wet treatment reduces the leaching of chloride and particularly sulfate by more than 60%. The release of typical contaminants for the treated MSWI BA such as the heavy metals Cu and Cr was well below 1% in the conducted leaching tests. An increase in the Sb concentration observed in the lysimeter experiments starting at L/S 0.75 L/kg and in the column experiment at L/S 4 L/kg is assumed to be related to decreasing concentrations of Ca and thus to the dissolution of sparingly soluble calcium antimonate. The same leaching mechanism applies with V, but the concentration levels observed are less critical regarding relevant limit values. However, on the long term the behavior of Sb could be problematic for the application of MSWI BA in construction.Graphic

Sorting Characteristics of Metals in Municipal Solid Waste Bottom Ash in Air Table Sorting

Sorting Characteristics of Metals in Municipal Solid Waste Bottom Ash in Air Table Sorting

Vitrification treatment of municipal solid waste bottom ash

This study involves the chemical characterization of municipal solid waste (MSW) bottom ash (BA) produced at a combustor facility in Rimini (Italy), and vitrification experiments, performed at lab scale under atmospheric conditions, maximum temperature of 1100 °C, for different durations (2–16 h). LA-ICP-MS analyses of the glasses obtained revealed that the overall volatility of metal elements increases with the time but it cannot be simply predicted by element boiling point. Elements have been here categorized into three different groups depending on their volatility comparing the glass product with the BA starting sample- high, medium or low, respectively- (1) Cu, W, Cl; (2) Pb, Zn, Sr; (3) Mo, Cr, V, Ni. The behavior of Cs, Rb, Ag, Ba, Ga, Co, U, Zr, Hf and Ta in the glassy slag is not defined because we did not observe statistically significant changes in their volatility behavior.Vitrification allows us to produce chemically stable glassy materials and immobilize potentially harmful elements, thus producing from waste new vitreous materials that are relatively inert and suitable for potential re-utilization in new products and/or applications for building and construction industries. Moreover, the samples show REE chondrite-normalized patterns indicating relative enrichments in Light-Rare Earth Elements (LREE), in particular La and Nd which may be interesting from an economic point of view in terms of waste recovery.Thus, the results obtained show how to treat bottom ashes from incinerator in order to provide more chemically inert and economically useful resources for recycle and reuse of solid waste BA.

Soluble Salt in Municipal Solid-Waste Incinerator Bottom Ash and Its Effect on the Performance of Cement-Stabilized Materials

The contents of soluble salts, including chloride and sulfate, were tested to use municipal solid-waste incinerator bottom ash (IBA) in cement-stabilized materials for roadbase. In addition, the effects of soluble salts on the strength properties of cement stabilized IBA and crushed stone mixture were analyzed by applying unconfined compressive and splitting strength tests, respectively. Moreover, the deformation properties of the mixture were analyzed by applying dry and temperature shrink tests, respectively. In addition, the microscopic mechanism of chloride and sulfate on the mixture was analyzed by using micro-test methods. Results show that the average contents of chloride and sulfate in IBA are 0.57% and 1.01%, respectively. The strength of the mixture that contains 30% IBA greatly decreases when the contents of chloride and sulfate in IBA are higher than 1.67% and 2.00%, respectively. The dry and temperature shrinkage deformations of the mixture greatly increase when the contents of chloride and sulfate are higher than 0.67% and 1.00%, respectively. Water treatment reduces the soluble salt content of IBA. Unlike the control mixture, the strength properties of the mixture that contained IBA with water treatment shows no remarkable difference, whereas the short and temperature shrinkage deformations increase and decrease, respectively. Microscopic analysis shows that Cl- reacts with cement hydration products to produce Friedel salts, and the amount of hydration products increases in the mixture due to the addition of chloride and sulfate. However, some cement particles are not hydrated when the Na2SO4 content is 1.0%. The content of soluble salts in IBA should be limited to ensure the performance of the mixture.

Long-term mechanical stability of cemented incineration bottom ash

Al2O3 is a major constituent of municipal solid waste (MSW) bottom ash that may cause swelling and weakening failure. This paper explores the influence of Al2O3 on the long-term mechanical properties of bottom ash. Experimental results indicate that increased Al2O3 corresponds to decreases in both the uniaxial compressive and tensile strengths of cemented bottom ash. More specifically, the strength and Young’s modulus of cemented bottom ash with high Al2O3 content (9.2%) decreased by 22.1% and 40.1%, respectively, after 365days. Therefore, the long-term mechanical stability of bottom ash with a high Al2O3 content is unsuitable for engineering applications.

Development of controlled low-strength material derived from beneficial reuse of bottom ash and sediment for green construction

Controlled low-strength material (CLSM) was newly designed using municipal solid waste bottom ash and dredged sediment as raw materials. Up to 80% of waste utilization by mass was achieved with all requirements fulfilled as general CLSM. The compressive strength of CLSMs made with bottom ash is generally higher than that of sediment. The formation of C–S–H gel contributes to the strength development and heavy metal immobilization from wastes. The heavy metal concentrations in the TCLP leachates of CLSM are far below the U.S.EPA regulatory standards, and the CLSMs are suitable for a wide range of construction applications.

Sinter-crystallization in air and inert atmospheres of a glass from pre-treated municipal solid waste bottom ashes

Glass powders, obtained after vitrification and milling of iron-rich Municipal Solid Waste Bottom Ashes (MSWA), were studied towards manufacture of sintered glass-ceramic material. The crystallization kinetics was investigated both in air and argon atmospheres by non-isothermal Differential Thermal Analysis (DTA). The densification behaviors at different temperatures were studied with optical dilatometry. The formed crystal phases were evaluated with X-ray diffraction (XRD) and the microstructure of samples were observed by scanning electron microscopy (SEM).The investigated composition is characterized with a high crystallization trend and formation of pyroxene solid solutions and melilite solid solutions. Due to additional nucleation process and lower viscosity (because of the lack of Fe2+ oxidation) the phase formation in inert atmosphere is accelerated and is carried out at lower temperature.In the interval 800–900°C the densification in both atmospheres is inhibited by the intensive phase formation. However, after increasing the sintering temperature up to 1120–1130°C secondary densification is carried out, resulting in material with zero water absorption, low closed porosity and high crystallinity. Some decreasing of sintering temperature and finer crystal structure are predicted at densification in inert atmosphere.

Assessment of mobility and bioavailability of contaminants in MSW incineration ash with aquatic and terrestrial bioassays

Incineration of municipal solid waste (MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction as well as a source of renewable energy. In the process fly and bottom ash is generated as a waste material. The ash residue may vary greatly in composition depending on the type of waste incinerated and it can contain elevated levels of harmful contaminants such as heavy metals. In this study, the ecotoxicity of a weathered, untreated incineration bottom ash was characterized as defined by the H14 criterion of the EU Waste Framework Directive by means of an elemental analysis, leaching tests followed by a chemical analysis and a combination of aquatic and solid-phase bioassays. The experiments were conducted to assess the mobility and bioavailability of ash contaminants. A combination of aquatic and terrestrial bioassays was used to determine potentially adverse acute effects of exposure to the solid ash and aqueous ash leachates. The results from the study showed that the bottom ash from a municipal waste incineration plant in mid-Sweden contained levels of metals such as Cu, Pb and Zn, which exceeded the Swedish EPA limit values for inert wastes. The chemical analysis of the ash leachates showed high concentrations of particularly Cr. The leachate concentration of Cr exceeded the limit value for L/S 10 leaching for inert wastes. Filtration of leachates prior to analysis may have underestimated the leachability of complex-forming metals such as Cu and Pb. The germination test of solid ash and ash leachates using T. repens showed a higher inhibition of seedling emergence of seeds exposed to the solid ash than the seeds exposed to ash leachates. This indicated a relatively low mobility of toxicants from the solid ash into the leachates, although some metals exceeded the L/S 10 leaching limit values for inert wastes. The Microtox® toxicity test showed only a very low toxic response to the ash leachate exposure, while the D. magna immobility test showed a moderately high toxic effect of the ash leachates. Overall, the results from this study showed an ecotoxic effect of the solid MSW bottom ash and the corresponding ash leachates. The material may therefore pose an environmental risk if used in construction applications. However, as the testing of the solid ash was rather limited and the ash leachate showed an unusually high leaching of Cr, further assessments are required in order to conclusively characterize the bottom ash studied herein as hazardous according to the H14 criterion.

ChemInform Abstract: Municipal Solid Waste Incinerator (MSWI) Concrete

AbstractReview: 103 refs.

Identifying the Advantages of Using Municipal Solid Waste Bottom Ash in Combination with Rice Husk and Bamboo Biochar Mixtures as Soil Modifiers: Enhancement of the Release of Polyphenols from a Carbon Matrix

Incineration is one of the most popular options used to treat waste in highly populated developed countries. It is crucial to find an environmentally acceptable alternative for the disposal of municipal solid waste incineration bottom ash (MSWIBA). The main objective of this study is therefore to investigate the value of biochar and MSWIBA mixtures as soil modifiers and determine their effects on plant growth, root yield, and the dry biomass weight of corn (Zea mays L.). Two different feedstocks (rice husks and bamboo) were used to produce the biochars applied in this test. Water-soluble phenol-based macromolecules (polyphenols) from woody raw materials would be enhanced to leach out metals under an alkali environment. In addition, extraction of polyphenols from a BA-mixed matrix and Z. mays L. dry biomass was performed. Polyphenol content was shown to increase when fertilizer was applied, inhibiting plant growth, root yield, and plant biomass dry weight. After applying fertilizer, the polyphenol content increased to 45-55 mg=L. Without the application fertilizer, however, the polyphenol content was 5-25 mg=L. A combination of BA and biochars added to soil seems to have the potential to improve the growth and yield of corn without the application of any chemical fertilizer. In addition, the BA-enhanced biochar degradation could be achieved through the results of this study. DOI: 10.1061/(ASCE)HZ.2153-5515.0000189. © 2013 American Society of Civil Engineers. CE Database subject headings: Bottom ash; Solid wastes; Mixtures; Recycling; Soil treatment. Author keywords: Municipal solid waste bottom ash; Incineration; Biochar; Polyphenols.

Co-gasification of municipal solid waste and material recovery in a large-scale gasification and melting system

This study evaluates the effects of co-gasification of municipal solid waste with and without the municipal solid waste bottom ash using two large-scale commercial operation plants. From the viewpoint of operation data, there is no significant difference between municipal solid waste treatment with and without the bottom ash. The carbon conversion ratios are as high as 91.7% and 95.3%, respectively and this leads to significantly low PCDD/DFs yields via complete syngas combustion. The gross power generation efficiencies are 18.9% with the bottom ash and 23.0% without municipal solid waste bottom ash, respectively. The effects of the equivalence ratio are also evaluated. With the equivalence ratio increasing, carbon monoxide concentration is decreased, and carbon dioxide and the syngas temperature (top gas temperature) are increased. The carbon conversion ratio is also increased. These tendencies are seen in both modes.Co-gasification using the gasification and melting system (Direct Melting System) has a possibility to recover materials effectively. More than 90% of chlorine is distributed in fly ash. Low-boiling-point heavy metals, such as lead and zinc, are distributed in fly ash at rates of 95.2% and 92.0%, respectively. Most of high-boiling-point heavy metals, such as iron and copper, are distributed in metal. It is also clarified that slag is stable and contains few harmful heavy metals such as lead. Compared with the conventional waste management framework, 85% of the final landfill amount reduction is achieved by co-gasification of municipal solid waste with bottom ash and incombustible residues. These results indicate that the combined production of slag with co-gasification of municipal solid waste with the bottom ash constitutes an ideal approach to environmental conservation and resource recycling.

The Calcination Process in a System for Washing, Calcinating, and Converting Treated Municipal Solid Waste Incinerator Fly Ash into Raw Material for the Cement Industry

ABSTRACT Calcination is the second step in a washing-calcination-conversion system in which treated municipal solid waste incinerator fly ash and bottom ash can be reused as raw material in the cement industry and can decompose or stabilize hazardous compounds, reduce residue amounts, and alter residue characteristics. In this research, only fly ash is discussed. Chloride reduction is important if treated fly ash is to be reused in cement; however, the relationship between washed fly ash properties and chloride reduction by calcination is not well understood. This study used washed residues of three types of fly ash—raw fly ash (RFA) from the boiler or economizer of an incineration system, fly ash collected in a bag filter injected with calcium hydroxide (Ca(OH)2) for acid removal (CaFA), and fly ash collected in a bag filter injected with sodium bicarbonate (NaHCO3) for acid removal (NaFA)—in calcination experiments with varying temperature (400–1100 °C) and atmosphere (100% nitrogen [N2] at 25 mL/min or 10% oxygen [O2] [90% N2] at fluxes of 25, 50, and 75 mL/min). From the perspective of chloride reduction, heating to 1000 °C with 1-hr heating time, 1-hr holding time, and an atmosphere of 10% O2/90% N2 was most suitable for calcination. Under these conditions, chloride levels were reduced by 91, 52, and 96% in washed residues of RFA, CaFA, and NaFA, respectively. Among the washed residues, the weight of the washed residue of NaFA decreased the most. IMPLICATIONS This research presents the reduction of chlorine and washing of three kinds of fly ash (RFA, CaFA and NaFA) during the calcination process. By comparing the results of those fly ashes, it is shown that NaHCO3 is better than Ca(OH)2 as a neutralization reagent to treat exhaust gas from an incineration chamber because chlorine is more easily eliminated from NaFA than from CaFA. The reduction of other elements is also presented, as well as the X-ray diffraction analysis of some samples by which the mechanism of the calcination process is analyzed.

Influence of Organic Matters on the Elution of Chroline in Municipal Solid Waste Bottom Ash

Influence of Organic Matters on the Elution of Chroline in Municipal Solid Waste Bottom Ash