Solid Waste Incineration Plant Research Articles

Catalytic Ozonation of Biologically Treated Leachate from Municipal Solid Waste in a Microbubble Reactor

ABSTRACTCatalytic ozonation using activated carbon (AC) as catalyst for advanced treatment of biologically treated leachate (BTL) from municipal solid waste incineration plant was carried out in a microbubble reactor. The removal efficiency of chemical oxygen demand (COD) in the leachate was significantly improved over that in the conventional bubble reactor. The effects of AC dosage, ozone concentration, ozone flowrate and liquid reaction temperature on COD removal efficiency were studied. The results show that the COD removal efficiency increased with increasing AC dosage, ozone flowrate and inlet ozone concentration, and the reactor liquid phase temperature has little effects on the COD removal efficiency. The maximum COD removal efficiency reached 89.87% in the AC/O3 system under the optimal conditions. The catalytic activity of the AC still remained stable after five cycles of use. Ultraviolet-visible (UV-Vis) spectra and GC-MS analysis indicated that the AC-catalyzed ozonation can enhance the efficiency of the organic pollutants; the mechanism of AC deactivation was explored using the variation of AC-specific surface area and X-ray diffraction analysis. In addition, the regeneration of AC was proved effective by hydrochloric acid leaching. These results show that the combination of a microbubble reactor with AC provided a highly efficient ozonation process for the BTL.

Intercomparison of the CALMET/CALPUFF Modeling System for Selected Horizontal Grid Resolutions at a Local Scale: A Case Study of the MSWI Plant in Krakow, Poland

Increase in grid resolution in atmospheric non-steady-state dispersion models induces a more faithful reflection of the area surface, and thus contributes to more detailed and diversified calculation results but also significantly prolongs the calculation time. This paper presents the influence of horizontal grid resolution in the CALMET/CALPUFF modeling system on the results of air quality impact assessment in a local scale carried out for the Municipal Solid Waste Incineration (MSWI) Plant in Krakow using the maximum permissible emission of NOx. Subject to comparative analysis were four grids of the following resolutions: 100, 250, 500 and 1000 m. A direct intercomparison of air concentrations was made for 676 discrete receptors with the use of statistical indicators. On the basis of the calculations and analyses, it has been stated that, depending on the regular grid spacing, some differences in calculated concentrations can occur affecting the results of the air quality impact assessment. The highest concentrations in all computational receptors present in the given case were obtained for 100 m grid spacing. When compared to a grid of 100 m, the relatively smallest discrepancies were obtained for a grid of 250 m, with an already significantly shortened calculation time.

Heterotrophic Nitrifiers Dominate Reactors Treating Incineration Leachate with High Free Ammonia Concentrations

Anaerobically treated leachate from municipal solid waste incineration plants contains extremely high free ammonia (FA) concentrations, which can hinder short-cut nitrification. pH adjustments made...

Mineralogy Characteristics and Heavy Metal Distribution of MSWI Fly Ash

Fly ash from municipal solid waste incineration (MSWI) plants can be categorized as a highly toxic mineral material due to the potential for leaching heavy metals. The mineralogical properties of MSWI fly ash visually reflect the heavy metals distribution in the ash, and are closely related to the release and migration behaviors of heavy metals in fly ash disposal or utilization scenarios. In order to understand the distribution of heavy metals in MSWI fly ash and provide support for heavy metals control technology, comprehensive tests on the macroscopic and microscopic mineralogical characteristics of the fly ash were conducted using X-ray diffraction (XRD), scanning electron microscope, a mineral liberation analysis system, and other methods. The results showed that MSWI fly ash was a heterogeneous material of closely combined mineral and non-mineral phases. The main mineral phases identified by XRD included chlorides and calcium-bearing minerals, mainly calcite and portlandite. The element distribution analysis, conducted with a mineral liberation analyzer, revealed that heavy metals of MSWI fly ash were mainly present in three forms:uniform distribution in the non-mineral amorphous phase, isomorphism in calcite and other minerals, and adsorption on the surfaces of quartz and hematite. Most content of Cu and Cr were distributed in the non-mineral phase due to their lower volatility, while most of semi-volatile heavy metals (43.92% of Zn and 60.61% of Cd) were present in mineral phases. In particular, Cd, Cr and Zn were mainly present in calcite, hematite and silicates respectively.

Source patterns and contamination level of polycyclic aromatic hydrocarbons (PAHs) in urban and rural areas of Southern Italian soils

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants. They have been identified as a type of carcinogenic substance and are relatively widespread in environment media such as air, water and soils, constituting a significant hazard for human health. In many parts of the world, PAHs are still found in high concentrations despite improved legislation and monitoring, and it is therefore vital defining their profiles, and assessing their potential sources. This study focused on a large region of the south of Italy, where concentration levels, profiles, possible sources and toxicity equivalent quantity (TEQ) level of sixteen PAHs were investigated. The survey included soils from five large regions of the south of Italy: 80 soil samples (0-20cm top layer) from urban and rural locations were collected and analysed by gas chromatography-mass spectrometry. Total PAHs and individual molecular compounds from the US Environmental Protection Agency priority pollutants list were identified and measured. Results showed that 16 PAHs varied significantly in urban and rural areas, and different regions presented discordant characteristics. Urban areas presented concentrations ranging from 7.62 to 755ngg-1 (mean = 84.85ngg-1), whilst rural areas presented ranges from 1.87 to 11,353ngg-1 (mean = 333ngg-1). Large urban areas, such as Rome, Naples and Palermo, exhibited high PAHs total concentration, but high values were also found in rural areas of Campania region. Different PAHs molecular ratios were used as diagnostic fingerprinting for source identification: LWMPAHs/HWMPAHs, Fluo/(Fluo + Pyr), BaA/(BaA + Chr), Ant/(Ant + Phe) and IcdP/(IcdP + BghiP). These ratios indicated that PAHs sources in the study area were mainly of pyrogenic origin, i.e. mostly related to biomass combustion and vehicular emission. On the other hand, values in Sicilian soils seemed to indicate a petrogenic origin, possibly linked to emissions from crude oil combustion and refineries present in the region. Finally, results allowed to calculate the toxicity equivalent quantity (TEQBAP) levels for the various locations sampled, highlighting that the highest values were found in the Campania region, with 661 and 54.20ngg-1, in rural and urban areas, respectively. These findings, which could be linked to the presence of a large solid waste incinerator plant, but also to well-documented illegal waste disposal and burning, suggest that exposure to PAH may be posing an increased risk to human health in some of the studied areas.

Modular life cycle assessment of municipal solid waste management

Life cycle assessment (LCA) is commonly applied to examine the environmental performance of waste management systems. The system boundaries are, however, often limited to either one tonne of material or to specific waste treatments and are, therefore, lacking a systems perspective. Here, a framework is proposed to assess complete waste management systems based on actual waste flows, assessed with a detailed material flow analysis (MFA) in a modular MFA/LCA approach. The transformation of the MFA into a product-process-matrix facilitates a direct link between MFA and LCA, therefore allowing for the assessment of variations in flows. To allow for an up-to-date and geographically specific assessment, 190 LCA modules were set up based on primary industrial data and the ecoinvent database. The LCA modules show where there have been improvements in different recycling processes over the past years (e.g. for paper recycling) and highlight that, from an environmental perspective, closed-loop recycling is not always preferable to open-loop recycling. In a case study, the Swiss municipal solid waste management system, of which there is already a detailed MFA, was modeled using the new LCA modules and applying the modular MFA/LCA approach. Five different mass flow distribution scenarios for the Swiss municipal solid waste management system were assessed to show the environmental impact of political measures and to test the sensitivity of the results to key parameters. The results of the case study highlight the importance of the dominant fractions in the overall environmental impacts assessment; while the metal fraction has the highest impact on a per kilogram basis, paper, cardboard, glass and mixed municipal solid waste were found to dominate the environmental impacts of the Swiss waste management system due to their mass. The scenarios also highlight the importance of the energy efficiency of municipal solid waste incineration plants and the credits from material substitution as key variables. In countries with advanced waste management systems such as Switzerland, there is limited improvement potential with further increases in recycling rates. In these cases, the focus of political measures should be laid on (i) the utilization of secondary materials in applications where they replace high-impact primary production, and (ii) an increased recovery of energy in waste-to-energy plants.

Magnetite enhances anaerobic digestion and methanogenesis of fresh leachate from a municipal solid waste incineration plant

Anaerobic digestion of municipal solid waste (MSW) incineration leachate is limited by high organic loading rates, high concentrations of complex organic matter, and the presence of compounds like ammonia, heavy metals, and salts that can inhibit microbial activity. The purpose of this study was to investigate whether the addition of magnetite could help reactors treating MSW incineration leachate overcome these limitations and promote efficient conversion of complex organic matter to methane. These studies showed that magnetite amendments improved chemical oxygen demand (COD) removal efficiencies (78.8% vs 89.0%) and methane production rates (3.7 m3STP/(m3·d) vs 4.8 m3STP/(m3·d)) at an organic loading rate (OLR) of 18.2 kg COD/(m3·d). Significant differences in microbial community structures were also observed between non-amended and magnetite-amended reactors. The majority of sequences from the magnetite-amended reactor clustered with acetogenic and mixed acid fermentative bacteria. Sequences from bacteria capable of extracellular electron transfer and methanogens from the genera Methanosarcina and Methanosaeta were also more abundant in magnetite-amended reactors. It is possible that these species were participating in direct interspecies electron transfer (DIET) facilitated by magnetite amendments. In addition, ammonia nitrogen, calcium, and heavy metals were lower in effluent collected from magnetite-amended reactors than non-amended controls, suggesting that magnetite adsorbed these inhibitory compounds and created an environment more amenable to microbial growth. These results are significant and should be used to develop strategies designed to optimize bio-methanogenic treatment of complex waste with elevated contaminant concentrations.

Quasi-targeted analysis of halogenated organic pollutants in fly ash, soil, ambient air and flue gas using gas chromatography-high resolution mass spectrometry with isotopologue distribution comparison and predicted retention time alignment

Identifying environmental pollutants, particularly emerging and new pollutants, in various matrices is a prerequisite for further research involving these pollutants. In this study, we developed a quasi-targeted analysis method to identify halogenated organic pollutants (HOPs) by joint application of gas chromatography-double focus magnetic-sector high resolution mass spectrometry (GC-DFS-HRMS), isotopologue distribution comparison and predicted retention time (PRT) alignment. Structures of a variety of unreported/scarcely reported HOPs were conceived and sketched, and then, multiple isotopologue ions of individual HOPs were detected by GC-DFS-HRMS in multiple ion detection mode. Comparisons between the detected mass spectra and the theoretically simulated isotopologue distributions were conducted via paired-samples T-test and cosine similarity analysis. PRT alignment was further applied to exclude interferences that presented unreasonable retention times. The method was validated with dozens of commercially available reference standards of conventional HOPs and several unintended byproducts comprising mix-chlorinated/brominated benzenes in some commercial halogenated-benzene standards, showing good reliability and accuracy. Application of the developed method was primarily implemented with fly ash from municipal solid waste incineration plants. In total, 106 molecular formulas corresponding to unknown or little-known HOPs were identified, of which many were mix-halogenated compounds. Six HOPs were structurally elucidated, including three sulfur-containing dioxin-like HOPs, two mix-perhalogenated benzenes, and a pentabrominated anisole. The structures of 18 compounds that individually contained 2–4 theoretical isomers were putatively elucidated according to the PRT alignment. In addition to fly ash, other environmental matrices, including soil, ambient air and flue gas, were screened by the method, and a number of HOPs were also found in these matrices. This method is feasible, reliable, accurate and sensitive for the identification and screening of potential unknown HOPs in the environment and should facilitate further research, such as pollution investigations and eco-environmental risk assessments for these pollutants.

Adverse pregnancy outcomes in women with changing patterns of exposure to the emissions of a municipal waste incinerator

Municipal solid waste incinerators emissions contain pollutants that, despite their low concentration, might adversely affect reproductive health. In the present study, we examined rates of miscarriage and birth defects among women who resided or were employed in the vicinity of a municipal solid waste incinerator plant from 2003 to 2013. In 2009, a progressive shutdown of the old incineration lines and operation of a new line caused considerably higher atmospheric release of polycyclic aromatic hydrocarbons, particularly of dioxins, due to these irregular operating conditions, technological renovation, and increased capacity. We used dioxin emission levels, based on a dispersion model, to define exposure status of the residing population to air pollutants emitted by the waste incinerator. In women who resided in areas characterized by higher emission exposures compared with a referent area, the relative risk (RR) of miscarriage was 1.04 (95% confidence interval (CI) 0.80–1.32) based on 62 cases overall, with little evidence of a dose-response relation. RRs were similarly null for both 2003–2008 and 2010–2013 periods (RR 1.12 (95% CI 0.80–1.53) and 0.98 (95% CI 0.63–1.48), respectively). Concerning birth defects in the offspring of women residing in the exposed area, no evidence of increased risk emerged, since the prevalence ratio at birth was 0.64 (95% CI 0.29–1.26), with comparable results in the 2003–2008 and 2010–2013 period. Corresponding analyses carried out in municipal residents who worked in the exposed area confirmed these findings. We also did not detect abnormally high rates of miscarriage and birth defects in the exposed cohorts in the single year 2009.Overall, these results do not suggest an effect of exposure to the emissions of the municipal solid waste incinerator we investigated on two indicators of reproductive health. However, the limited statistical stability of the estimates and the absence of individual-based information on some potential confounders suggest caution in the interpretation of study findings.

Emission characteristics of PCDD/Fs in stack gas from municipal solid waste incineration plants in Northern China

Emission characteristics including congener's profile, gas emissions and toxic equivalent concentration (TEQ) indicators of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in 57 stack gas samples from 6 municipal solid waste incinerators (MSWIs) in Northern China were investigated by gas chromatography-high resolution mass spectrometry (HRGC-HRMS). Additionally, PCDD/Fs formation mechanisms from the MSWIs were briefly discussed. Results revealed that the concentrations and equivalent concentrations of PCDD/Fs emissions in stack gas from 6 MSWIs were in the range of 0.11–2.53 ng Nm−3 and 0.007–0.059 ng TEQ Nm−3, respectively. The emission factors of PCDD/Fs from 6 MSWIs varied from 0.027 to 0.225 μg I-TEQ tonne−1, with a mean value of 0.17 μg I-TEQ tonne−1 waste, which was estimated to an annual emission of 234.96 mg I-TEQ of PCDD/Fs from 6 MSWIs to the atmosphere. O8CDD, O8CDF and 1,2,3,4,6,7,8-H7CDD were the indicatory compounds of PCDD/Fs to apportion the sources of PCDD/Fs in environmental medium especially in ambient environment of MSWIs. 1,2,3,7,8,9-H6CDF and 1,2,3,4,7,8-H6CDF can be used as TEQ indicators for monitoring PCDD/Fs emission. Based on the positive matrix factorization (PMF) model, eight factors were extracted by the PMF analysis. Formation of low-chlorinated PCDDs (1,2,3,7,8-P5CDD, 1,2,3,4,7,8-H6CDD, 1,2,3,6,7,8-H6CDD and 1,2,3,7,8,9-H6CDD) possessed strong correlation, and the chlorophenols maybe the important precursors of low-chlorinated PCDDs, which were generated within the low chlorinated content. Penta- and hexa-PCDFs formation in stack gas from MSWI may block catalytic sites for PCDFs formation from carbon. Meanwhile, possible formation mechanisms of high-chlorinated PCDDs (hepta- and octa-PCDDs) and high-chlorinated PCDFs (hepta- and octa-PCDFs) were respectively dependent.

Microbial Communities and Sludge Specific Resistance in Two SBRs Treating Leachate

The relationship between microbial populations and sludge filtration performance was studied when active sludge was used to treat the leachate from municipal solid waste incineration plants. Two SBRs (SBR1 and SBR2) were operated at the same conditions, except that SBR1 was exposed to the sunlight and SBR2 was in the dark. To identify the difference in microbial populations in two reactors, high-throughput sequencing method was used. On the 50th day, the fungi abundance in SBR2 was higher than in SBR1. Phylum Rozellomycota became the dominant fungi in SBR1, whose relative abundance was 83.71%. Phylum Basidiomycota and Genus Trichosporon became only dominant fungi in SBR2, whose relative abundances were 99.84% and 99.78%, respectively. Bacterial abundance in SBR1 was higher than in SBR2. In SBR1, Thauera was the major bacterial genus, whose relative abundance was 39.35%. In SBR2, Planktosalinus, Thauera, and Ottowia were the major bacterial genera, whose relative abundances were 16.84%, 16.23%, and 12.55%. Rotifers and other predatory metazoan were detected on the 30th-50th days in SBR1 and sludge specific resistance began to decline on the 35th day. Filamentous fungi bulking caused by Trichosporon resulted in a continuous increase in sludge specific resistance of SBR2. The dominant microbial communities (especially fungi) and sludge specific resistances in SBR1 and SBR2 were very different because of the effect of sunlight. Therefore, sunlight plays an important role on microbial communities and sludge characteristics.

Influence of Salinity and Pb on the Precipitation of Zn in a Model System

Fly ash from solid waste incineration plants is a source of a significant mass flow of Zn- and Pb-containing waste. Acidic leaching removes most heavy metals from fly ash, but leads to high concentrations of soluble salts in the solution, resulting in a saline solution enriched in heavy metals. Common treatment methods cause voluminous sludge that is mostly disposed of as hazardous waste and hence leads to a loss of Zn and other heavy metals. On a laboratory scale, precipitation experiments with 2000 mg/L Zn were performed to investigate the impact of salinity (0 to >70,000 mg/L Cl, 0 to 5400 mg/L SO4) and Pb concentration (0 to 800 mg/L) on the formation of mineral phases. The removal efficiency of Zn and Pb after alkalization of the solution was studied. Characterization of the precipitates showed that salinity has a significant impact on the phases produced. At a low salt concentration, zincite (ZnO) is formed. With increasing salinity, the higher concentration of chloride and sulfate increases the stability of various Zn sulphate hydroxides. At a medium salinity of 7000 mg/L, bechererite is predominantly formed, whereas a higher salinity leads to the formation of gordaite. Addition of low amounts of Pb enlarges the stability field of zincite to medium saline solutions but causes lower removal efficiency. The lower removal efficiency observed at low salinity increases at a higher salinity. In high saline solutions, high Pb concentrations (800 mg/L) are needed to form laurionite, a Pb-hydroxychloride phase.

Influence of Air Pollution Control (APC) Systems and Furnace Type on the Characteristics of APC Residues from Municipal Solid Waste Incinerators

The characteristics of air pollution control (APC) residues are influenced by the furnace type, APC system, and waste composition. In this study, the characteristics of APC residues from nine municipal solid waste incineration plants (the compositions of incinerated solid waste are similar) with different furnace types and APC systems were compared.APC residues contain a great amount of Ca and Cl, and the contents of Al, Si, and Fe in the APC residues from fluidized bed incinerators are higher. The mineral compositions of APC residues are not influenced by the flue gas treatment process, but their contents vary. The contents of Cd, Pb, and Zn in the APC residues from fluidized bed incinerators are lower, while those of Cr, Ba, Cu, and Ni are greatly influenced by the APC systems, with the "grate+dry scrubber" APC residues having the lowest values. The differences in the heavy metal contents in the APC residues from two incinerators before and after the upgrading of the APC systems are not significant. The leaching toxicity of Pb in the APC residues from grate incinerators is higher than that from fluidized bed incinerators, while some elements with low contents in fluidized bed APC residues can be leached more in acetic acid buffer solution. The acid neutralization capacity of the APC residues is related to Ca content. The leaching concentrations of most heavy metals are significantly increased under strong acidity (Cd, Ni, and Zn:leachate pH < 8; Pb, Cu, and Cr:leachate pH < 4). The maximum leaching concentrations of As, Ba, Cu, Ni, and Pb in the APC residues from grate incinerators are mainly controlled by their total content. The leaching concentrations of As, Ba, Cu, Ni, and Pb in the APC residues from fluidized bed incinerators are lower than those from grate incinerators with similar metal contents, which may be due to their different chemical speciation influenced by furnace types and the complexation with Al and Fe compounds.

Properties of cold-bonded lightweight artificial aggregate containing bottom ash with different curing regime

Cold-bonded pelletizing technique is frequently used in aggregate manufacturing process as it can minimise the energy consumption. It has contributed to both economical and environmental advantages because it helps to reduce the gas emissions problems. Bottom ash collected from municipal solid waste incineration (MSWI) plant was selected as raw material in this study and was utilised as a partial replacement for cement for artificial aggregate production. Several percentage of ash replacement was selected ranged from 10 to 50%. Aggregate pellets were subjected to different types of curing condition which is room-water (RW), room-room (RR), oven-room (OR) and oven-water (OW) condition. Properties of aggregate pellets were examined to obtain its density, water absorption, aggregate impact value (AIV) and specific gravity (SG). The results indicated that the most efficient curing regime is by exposing the aggregate in RW condition. The optimum aggregate was selected at 20% where it has satisfied the required density of 739.5kg/m3, and classified as strong aggregate with AIV 14. However, the water absorption of aggregate increased proportionately with the increment of ash content.

Health Risk Assessment and Correlation Analysis on PCDD/Fs in the Fly Ash from a Municipal Solid Waste Incineration Plant

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fly ash may pose health threats to onsite workers due to their inevitable dispersion in the working environments during recycling and disposal of fly ash from Municipal Solid Waste Incinerators (MSWIs). Here, PCDD/Fs in fly ash from an MSWI in Southern Taiwan was analyzed from several perspectives. The results can be summarized as follows: (1) Through multiple comparison analyses, it was revealed that four types of congeners (OCDD, OCDF, 1,2,3,4,6,7,8-HpCDD and 1,2,3,4,6,7,8-HpCDF) have significantly higher concentrations than other species (p < 0.01). (2) 2,3,4,7,8-PeCDF represented the main contributor to the total toxic equivalent concentration (TEQ). The top three candidate indicators of total TEQ are OCDF, 1,2,3,4,6,7,8-HpCDF and 2,3,4,7,8-PeCDF, in which OCDF might be most powerful indicator of fly ash from similar sources. (3) It was indicated that all congeners correlated positively with each other (with R2 values in the range between 0.707–0.939); Meanwhile, the results of the cluster analysis unveiled the specific features of several congeners (such as 1,2,3,7,8,9-HxCDF, OCDD and OCDF). (4) Through assessing health risk with a Monte Carlo simulation, both the 95th percentile carcinogenic risk (CR) and non-carcinogenic risk (non-CR) for onsite workers exceeded the threshold limit and should be considered as significant risks for onsite workers. (5) The results of the sensitivity analysis suggested that concentration (CC) and exposure duration (ED) were the two most sensitive parameters in both the CR and non-CR assessment. The above findings could be useful for improving existing health risk mitigation/management strategies for onsite workers in waste incineration plants.

Advanced exergy analysis and environmental assesment of the steam cycle of an incineration system of municipal solid waste with energy recovery

This work presents an advanced exergy and environmental analysis of a steam cycle of a municipal solid waste incineration plant, with energy recovery for electricity generation; employing MSW of the city of Santo André in São Paulo State, Brazil. Initially, a plant energy analysis is accomplished to determine some thermodynamic performance indicators, as well a conventional exergetic analysis is performed, to determine the magnitude of exergy destruction in each one of plant main components. To identify the potential for improvement in the incineration steam cycle, an advanced exergetic analysis was done, with exergy destruction divided into four categories: endogenous, exogenous, avoidable and unavoidable. With all this it was calculated that total plant exergy destruction can be reduced by 8.4%, through increments in efficiency in plant components taking into account best existing technologies and operating parameters that represent an avoidable total cost of $2′830,624 per year.Finally, a Life Cycle Analysis using the IMPACT Method 2002 + was carried out to determine environmental impacts of plant operation considering two cases: Reference Case (Case A) and the Improved One (Case B). Case B was divided in three comparative scenarios (B1, B2 and B3) which were considered to evaluate the environmental impact of plant operation and dislocation of primary energy. The results shows that reduction of avoidable exergy destruction in a steam generating cycle leads to an emission index reduction from 531 to −224 kg CO2eq/MWh, while a primary energy displacement about 3.69 kWh per unit of electric energy available was reached, using MSW as fuel in steam cycle.

H2S adsorption by municipal solid waste incineration (MSWI) fly ash with heavy metals immobilization

As a byproduct of municipal solid waste incineration (MSWI) plant, fly ash is becoming a challenge for waste management in recent years. In this study, MSWI fly ash (FA) was evaluated for the potential capacity of odorous gas H2S removal. Results showed that fly ash demonstrated longer breakthrough time and higher H2S capacities than coal fly ash and sandy soil, due to its high content of alkali oxides of metals including heavy metals. H2S adsorption capacities of FA1 and FA2 were 15.89 and 12.59 mg H2S/g, respectively for 750 ppm H2S. The adsorption of H2S on fly ash led to formation of elemental sulfur and metal sulfide. More importantly, the formation of metal sulfide significantly reduced the leachability of heavy metals, such as Cr, Cu, Cd and Pb as shown by TCLP tests. The adsorption isotherms fit well with Langmuir model with the correlation coefficient over 0.99. The adsorption of H2S on fly ash features simultaneous H2S removal and stabilization and heavy metals found in most MSWI fly ash, making fly ash the potential low cost recycled sorbent material.

Pollution Characteristics, Source Analysis and Potential Ecological Risk Assessment of Heavy Metals in Soils Surrounding a Municipal Solid Waste Incineration Plant in Shanghai

The contents of ten heavy metals (As, Cu, Cd, Cr, Pb, Ni, Zn, Ti, Mn, and Hg) were determined in the surface soils surrounding a municipal solid waste incineration plant in Shanghai using atomic spectroscopy. The spatial distribution and sources of the detected heavy metals were studied by enrichment factor and multivariate statistical and spatial interpolation analyses. In addition, their potential ecological risk was assessed. The results showed that all heavy metals, except Hg and As, were detected with mean contents ranging from 0.399 to 4220 mg·kg-1. The mean contents of Cu, Cd, Cr, Pb, Ni, Zn, and Mn were higher than their respective background values in Shanghai. In particular, the mean content of Cd was 2.9 times its background value. The results of the Pearson's correlation, principle component, enrichment factor, and spatial distribution analyses of these heavy metals indicated that Ti, Mn, and Ni primarily originated from natural sources, while Cd, Cr, Cu, Pb, and Zn originated from industrial manufacturing, combustion, and traffic emissions. The potential ecological risk assessment showed that soils surrounding the municipal solid waste incineration plant suffered from a moderate-level risk. The mean value of the potential ecological risk index of these detected heavy metals was 108.92, of which Cd contributed as high as 79.63%, deserving much attention.

Characterization of ash deposits from municipal solid waste (MSW) incineration plants

In this work, chemical compositions and micro morphologies and structures of ash deposits from two municipal solid waste-to-energy (WtE) plants in Norway were analyzed and characterized. The ash deposits were sampled from different locations in the combustion chamber. The samples were analyzed by a combination of a scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray fluorescence (XRF). The samples collected from locations close to the grate contain high concentrations of Ca and Si. Concentrations of K, Na, Cl and S in the deposits sampled from the top of the combustion chamber are significantly high. A layered structure can be seen from the deposit samples. The inner layer closer to or directly in contact with a heat transfer tube surface can be considered as primary deposits that have high concentrations of Cl, S, K and Na. The primary deposit layer has dense and compact structure due to the sintering and melting of deposited ash particles and grains. Together with XRF analysis, the SEM-EDX analysis revealed that the primary deposits are probably formed due to deposits of fused sulfates and chlorides on the heat transfer tube surfaces. The outer layer of the ash deposits has more loose structure formed due to agglomeration of smaller size grains. SEM-EDX and XRF analyses showed that the Ca, Si, Al and S are dominant elements in these large grains, indicating existence of calcium sulfates, silicates and calcium and silicon oxides.

Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications

Catalysts used for selective catalytic reduction were deactivated for various times in a slipstream from a municipal solid waste incineration plant and then characterized. The activity for NO reduction with NH3 was measured. The Brunauer–Emmett–Teller surface areas were determined by N2 adsorption from which the pore size distributions in the mesopore region were obtained. Micropore areas and volumes were also obtained. The composition of fresh and deactivated catalysts as well as fly ash was determined by atomic absorption spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. The changes in surface area (8% decrease in BET surface area over 2311 h) and pore structure were small, while the change in activity was considerable. The apparent pre-exponential factor was 1.63 × 105 (1/min) in the most deactivated catalyst, compared to 2.65 × 106 (1/min) in the fresh catalyst, i.e. a reduction of 94%. The apparent activation energy for the fresh catalyst was 40 kJ/mol, decreasing to 27 kJ/mol with increasing deactivation. Characterization showed that catalytic poisoning is mainly due to decreased acidity of the catalyst caused due to increasing amounts of Na and K.Graphical