Characteristics of industrial and laboratory meat and bone meal ashes and their potential applications

This paper reports the characterization of four meat and bone meal (MBM) ashes obtained from specific incineration (laboratory) and from co-incineration (industrial process). Three out of the four MBM ashes were mainly composed of calcium phosphates (hydroxyapatite and whitlockite). Their compositions (major and trace) were in the range for natural phosphate rocks. Trace element contents, including heavy metals, were below 0.6% and industrial ashes contained much more heavy metals than laboratory ash. The amounts of leached elements were low, especially for laboratory ash. According to the European classification of waste to be landfilled, the laboratory ash can be classified as an inert waste. Two industrial ashes are mostly inert. Only one ash is highly leachable and needs a stabilization treatment to be classified at least in the category of hazardous waste. It seems, from these results, that possibilities other than landfilling could be considered to give economic value to these ashes.     

Comparison of the characteristics of bottom and fly ashes generated from various incineration processes

This study analyzed and compared the characteristics of bottom and fly ashes from three municipal solid waste incinerators (MSWIs) in Taiwan. Different incineration furnaces were investigated, including: (1) fluidized bed, (2) mass-burning, and (3) mass-burning linked rotary kiln. The particle size distribution, morphology, mineralogical and chemical composition, and leaching behavior of heavy metals of ash samples were evaluated. The results revealed that three types of incineration processes have different characteristic for ashes due to transportation and mixing system inside furnace. Particle size distribution indicated that 28.5% of MSWI-B bottom ash has lower than 180 microm and 61.2% of MSWI-A fly ash has larger than the 250 microm. The leaching concentration of Pb exceeded the regulatory level set by the Taiwan EPA in fly ashes from MSWI-B and MSWI-C, and thus must be considered hazardous wastes. Specifically, the leaching concentration of heavy metals of fly ashes from MSWI-A (fluidized bed incinerator) was lower than that of the others, and was corresponded to the regulatory levels. Therefore, a fluidized bed incineration process appears a potential of handling heavy metals for ashes. The result was also provided the valuable information for incinerator design and operation.     

Heavy metal vaporization and abatement during thermal treatment of modified wastes

This study examines the vaporization percentage and partitioning of heavy metals Cd, Pb and Zn during thermal treatment of wastes with added PVC, heavy metals or phosphate, and the efficiency of sorbents for removal of these metallic compounds in flue gas of an industrial solid waste incinerator. Firstly, vaporization experiments were carried out to determine the behavior of heavy metals during combustion under various conditions (type of waste, temperature, presence of chloride or phosphate ...). The experimental results show relatively high vaporization percentage of metallic compounds within fly ash and limestone matrix while heavy metals within sediments treated with phosphoric acid are less volatile. Vaporization of metals increases with increasing temperature and with chloride addition. The thermal behavior of the selected heavy metals and their removal by sorbents (sodium bicarbonate, activated carbon) was also studied in an industrial solid waste incinerator. These pilot scale experiments confirm that heavy metals are concentrated in fly ashes and cyclone residues, thus effectively controlling their release to the atmosphere.     

Experimental and thermodynamic investigation on transfer of cadmium influenced by sulfur and chlorine during municipal solid waste (MSW) incineration

We used two approaches to investigate the impact of sulfur and chlorine compounds on transfer of a semivolatile heavy metal, cadmium, during municipal solid waste (MSW) incineration: experiments using a tubular furnace reactor and thermodynamic equilibrium calculations. Artificial wastes representative of typical MSW in China with and without the presence of sulfur and chlorine compounds were combusted at 850 degrees C, and the partitioning of Cd among bottom ash, fly ash and flue gas was quantified. The results indicate that sulfur compounds in the elemental form and reduced state could stabilize Cd in the form of CdS due to local reducing environment, while sulfur in the oxidized forms slightly increased Cd volatilization during incineration. In contrast, the presence of chlorine compounds significantly increased the partitioning of Cd on fly ash. Chemical equilibrium calculations show that sulfur binds with Cd and alters Cd speciation at low temperatures (<700 degrees C), while chlorine significantly increases the volatilization of Cd through formation of volatile CdCl(2) and thus its partitioning on the fly ash between 400 and 1000 degrees C. The equilibrium calculation results also suggest that SiO(2)- and Al(2)O(3)-containing minerals could function as sorbents stabilizing Cd as condensed phase solids (CdSiO(3) and CdAl(2)O(4)). These findings provide useful information on understanding the partitioning behavior of Cd and can help development of strategies to control volatilization of Cd during MSW incineration.     

Characterization of air pollution control residues produced in a municipal solid waste incinerator in Portugal

This study is mainly related with the physical and chemical characterization of a solid waste, produced in a municipal solid waste (MSW) incineration process, which is usually referred as air pollution control (APC) residue. The moisture content, loss on ignition (LOI), particle size distribution, density, porosity, specific surface area and morphology were the physical properties addressed here. At the chemical level, total elemental content (TC), total availability (TA) and the leaching behaviour with compliance tests were determined, as well as the acid neutralization capacity (ANC). The main mineralogical crystalline phases were identified, and the thermal behaviour of the APC residues is also shown. The experimental work involves several techniques such as laser diffraction spectrometry, mercury porosimetry, helium pycnometry, gas adsorption, flame atomic absorption spectrometry (FAAS), ion chromatography, scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD) and simultaneous thermal analysis (STA). The results point out that the APC residues do not comply with regulations in force at the developed countries, and therefore the waste should be considered hazardous. Among the considered heavy metals, lead, zinc and chromium were identified as the most problematic ones, and their total elemental quantities are similar for several samples collected in an industrial plant at different times. Moreover, the high amount of soluble salts (NaCl, KCl, calcium compounds) may constitute a major problem and should be taken into account for all management strategies. The solubility in water is very high (more than 24% for a solid/liquid ratio of 10) and thus the possible utilizations of this residue are very limited, creating difficulties also in the ordinary treatments, such as in solidification/stabilization with binders.     

A comparision of regulated chemicals versus emitted PICs and PICs for risk analysis

In general, toxic combustion byproducts (TCBs) are the unwanted residues remaining in flue gases, combustion ashes, and wastewaters from the operation of an incineration or combustion facility. If a combustor is not well designed and operated, it may emit too high a level of TCBs. Categories of TCBs and some example constituents are as follows:

1. 1. Acid gas: HCl, NO_x and SO₂;

2. 2. Organics: Hydrocarbons such as dioxins and furans (PCDDs and PCDFs);

3. 3. Particulates: Trace metals (conventional metals and radioactive metals) and soots;

4. 4. Contaminants in ash; and

5. 5. Contaminants in spent wastewater.

Pollutants in Category (2) above are generally considered to be the products of incomplete combustion (PICs) in the field of hazardous waste incineration.

TCBs has been one of the major technical and sociological issues surrounding the use of incineration as a waste treatment alternative. Because of the complexity and controversy, the U.S. EPA issued a draft “Combustion Strategy” on May 18, 1993. The objective of the “Combustion Strategy” was to address the needs of and to outline the approaches for upgrading the existing incineration standards to better control TCB emissions.

This article lists those chemicals and metals which are regulated by two major U.S. environmental laws, namely, the Clean Air Act Amendments (CAAA) of 1990 and the Resource Conservation and Recovery Act (RCRA) of 1976. The CAAA is to regulate the air emissions from major sources, and the RCRA is to protect human health and the environment from the management of solid wastes, particularly from waste incineration. This paper also lists the PIC chemicals that were studied under U.S. EPA incineration research programs in the 1980s and the PIC chemicals that EPA permit writers are considering be the subject of risk analyses during the process of industry's applying for an incinerator operating permit.     

Partitioning characteristics of targeted heavy metals in IZAYDAS hazardous waste incinerator

Partitioning of eight targeted heavy metals (Cr, Mn, Cu, Pb, Sn, Co, Ni and Zn) was carried out during five trial burns in Izmit hazardous and clinical waste incinerator (IZAYDAS). Metal contents of the original wastes and their concentration in the bottom ash (BA), fly ash (FA), filter cake (FC) and flue gas were determined. Partitioning behavior of metals during the two-stage incineration was evaluated with respect to physico-chemical properties of feed waste and metals, and the operational conditions. Results suggest that combustion temperatures and retention times are the dominant parameters determining the volatility of metals in the first combustion chamber. Targeted metals were generally partitioned in the rank of bottom ash, filter cake, fly ash and flue gas. High filter cake/fly ash ratios showed that high temperatures in the second stage increase both the formation of gaseous metallic compounds and the enrichment of metals in fine particles. Since ESP could not be effective in removing fine particles and volatilized metallic compounds, the necessity of an additional system that would remove heavy metals efficiently was emphasized for the modern incinerators.     

Thermal treatment of harzardous waste for heavy metal recovery

In this study, a new method for recovering heavy metals from hazardous waste is introduced. The process is characterized by a separation of heavy metals and residues during the thermal treatment under a sub-stoichiometric atmosphere in a rotary kiln. After leaving the rotary kiln the separated heavy metals are precipitated in a hot gas ceramic filter. Using this technology, hazardous materials, both liquids and pasty hazardous waste containing heavy metals, can be treated and a product with a quasi-raw material condition can be formed. In contrast to current methods,the harmful substances should not be immobilized and disposed. In fact, a saleable product highly concentrated with heavy metals should be formed. During preliminary investigations with a solution containing sodium chromate tetrahydrate, the process was tested in a pilot plant. Here,the separation of chromium could be demonstrated with leaching tests and characterization of the filter dust. Analysis concerning the disposability of the residues had not been carried out because only the process and the characteristic of the filter dust were in the centre of attention.     

SEM/EDS and XRD characterization of raw and washed MSWI fly ash sintered at different temperatures

The disposal of fly ash generated during municipal solid waste incineration (MSWI) may pose a significant risk to the environment due to the possible leaching of hazardous pollutants, such as toxic metals. Sintering technology attracted more attention than the vitrification process because of its low energy needed. Generally, a preliminary washing treatment of raw fly ash with water was necessary for this sintering technology. This study investigated the composition and morphology of raw fly ash (RFA) and washed fly ash (WFA) at different sintering temperatures, and examined the newly formed minerals during sintering. Toxicity characteristic leaching procedure (TCLP) tests were carried out to investigate the effect of the washing treatment and sintering process on the leaching performance of heavy metals in fly ash. Results showed that, with an increase of sintering temperature more complex aluminosilicates were formed; the incorporation of Mg, Fe and Pb into the aluminosilicates occurred during the sintering process at higher temperatures (800 and 900 degrees C). The washing treatment reduced the leachable concentration of Cd, Pb and Ni, but increased that of Cr. A CaCrO(4) compound was considered as a potential soluble species.     

Characteristics of air pollution control residues of MSW incineration plant in Shanghai

A unique type of waste--air pollution control (APC) residues--has received increasing attention in China since the first large-scale incinerator, Shanghai Yuqiao municipal solid waste (MSW) incineration plant, was installed in the country in 2002. The APC residues of this particular plant are similar to other residues that will be produced in other incineration plants under construction in China. This work examines for the first time the benchmark contaminants of APC residues from the Yuqiao Plant, with reference to soluble salts, heavy metals and dioxins. Experimental findings reveal that the residues contained a marked amount of soluble salts, of up to 17.4-21.9% (mostly chlorides), 0.98-1.5 ngTEQ/gash of dioxins and various heavy metals. Lead is of particular concern, and requires stabilization before disposal. Heavy metal speciation schemes were implemented herein to determine the leaching characteristics. The correlation between the amounts of soluble salts or chemical speciation of the heavy metals and the leaching toxicity of these heavy metals in the residues is considered.     

Energy recovery from heavy ASR by co-incineration in a fluidized bed combustor

Automotive shredder residue (ASR) is a heterogeneous waste stream with varying particle size and elemental composition. Owing to its complexity and hazardous characteristics, landfilling of ASR is still a common practice. Nevertheless, incineration with energy recovery of certain ASR fractions (Waste-to-Energy, WtE) emerges as an interesting alternative. In a full scale experiment, a waste mix of 25 % heavy ASR, 25 % refuse derived fuel (RDF), and 50 % waste water treatment (WWT) sludge was incinerated in the SLECO fluidized bed combustor (FBC) at the Indaver site in Antwerp, Belgium. Input and output streams were sampled and analyzed to make an inventory of the most important pollutants and toxics. The inventory was further used to determine the environmental impact. Results are compared to those of two other scenarios: incineration of the usual waste feed (70 % RDF and 30 % WWT sludge) and co-incineration of 39 % ASR with 61 % WWT sludge. It can be concluded that co-incineration of heavy ASR in an existing FBC is a valid and clean technology to increase current reuse and recovery rates. In the considered FBC, 27 % of the energetic value of ASR can be recovered, while all emissions remain well below regulatory limits and only 12.6 % of the heavy ASR needs to be landfilled. The proportion of ASR in the input waste mix is however limited by the heavy metal concentration in the ASR and the generated ashes.     

Highly acidic phosphorus-containing porous carbons: synthesis and physicochemical properties

Phosphorus-containing carbon porous materials were obtained by pyrolysis of sucrose in the presence of phosphoric acid at a temperature 400 and 800 °C. Synthesized samples were characterized by elemental analysis, infrared spectroscopy, nitrogen adsorption–desorption, the measurement of cation-exchange capacity (CEC) and sorption capacity for lead ions, potentiometric titration. It was shown that phosphorus-containing carbon sorbents have acidic properties and they are characterized by high cation-exchange capacity (up to 5.9 mmol/g). The samples which were synthesized at 800 °C have the highest content of acid groups, as well as phosphorus and oxygen. Detected surface acidic groups are phosphorus-containing (pК ~1.7–1.9) and represent residua of acid phosphates and polyphosphates, connected with carbon framework. High CEC of synthesized materials can be attributed to a significant degree of phosphorylation of sucrose through the large number of hydroxyl groups. P-containing acid groups on the surface of carbon framework provide high adsorption of heavy metals ions (in particular lead). Thus, the obtained P-containing carbon sorbents can be used as effective cation-exchangers for the removal of cations of heavy metals from aqueous solutions.     

Influence of flue gas SO2 on the toxicity of heavy metals in municipal solid waste incinerator fly ash after accelerated carbonation stabilization

The influence of CO₂ content and SO₂ presence on the leaching toxicity of heavy metals in municipal solid waste incinerator (MSWI) fly ash was studied by examining the carbonation reaction of MSWI fly ash with different combinations of simulated incineration flue gases. Compared with raw ash, the leaching solution pH of carbonated ash decreased by almost 1 unit and the leaching concentrations of heavy metals were generally lower, with that of Pb decreasing from 19.45 mg/L (raw ash) to 4.08 mg/L (1# carbonated ash). The presence of SO₂ in the incineration flue gas increased the leaching concentrations of heavy metals from the fly ash to different extents after the carbonation stabilization reaction. The pH of the leaching solution was the main factor influencing the leaching concentrations of heavy metals. The increase in buffer capacity with the pH of carbonated ash caused an increase in heavy metal stability after the carbonation reaction. Accelerated carbonation stabilization of MSWI fly ash could reduce its long-term leaching concentrations (toxicity) of Cu, Pb, Se, and Zn. The leaching concentrations of heavy metals from carbonated ash also likely had better long-term stability than those from raw ash. The presence of SO₂ in the incineration flue gas increased the proportion of exchangeable state species of heavy metals; slightly increased the long-term leaching toxicity of Cu, Pb, Se, and Zn; and reduced the long-term stability of these metals in the fly ash after the carbonation reaction.     

Insights of CMNPs in water pollution control

The various toxic contaminants such as dyes, heavy metals, pesticides, rare‐earth elements, and hazardous chemicals are the major threats to all the flora and fauna. Owing to the harmful ill effects caused by the toxic contaminants, it is necessary to eliminate these compounds from the authors’ ecosystem. The chitosan magnetic nanomaterials (CMNPs) are one of the superior materials used in the wastewater treatment through various conventional technologies. The chitosan is a natural source obtained from the crustacean shells of crabs, prawns etc. The magnetic nanomaterial prepared by the reinforcement of chitosan is highly effective in the removal of heavy metals, dyes, organic matter, and harmful chemicals. It is used in various technologies such as adsorption, flocculation, immobilisation, photocatalytic technology, and bioremediation. This possesses unique surface and magnetic characteristics, Moreover, it is simple, economically feasible, and eco‐friendly material used efficiently in wastewater treatment. This review paper depicts the overview of CMNP in the industrial effluent treatment.Inspec keywords: effluents, adsorption, dyes, water pollution control, wastewater treatment, nanofabrication, nanoparticles, catalysis, industrial waste, photochemistry, flocculation, contamination, magnetic particlesOther keywords: CMNPs, water pollution control, toxic contaminants, dyes, heavy metals, pesticides, rare‐earth elements, hazardous chemicals, flora, fauna, chitosan magnetic nanomaterials, wastewater treatment, natural source, magnetic nanomaterial, organic matter, harmful chemicals, photocatalytic technology, magnetic characteristics, eco‐friendly material, industrial effluent treatment     

Disposal of MSWI fly ash through a combined washing-immobilisation process

The objective of this work was to investigate the feasibility of a combined washing-immobilisation process as a means of optimising the disposal of fly ash resulting from municipal solid waste incineration (MSWI) in cementitious matrices. Two different types of Italian MSWI fly ash and an ordinary Portland cement (ASTM Type I) were used. Washing pre-treatment of fly ash with water always produces a wastewater that can be successfully treated by reducing the pH to values of 6.5-7.5. This treatment is capable of removing the detected contaminants (Al, Cd, Pb, Zn) through two different mechanisms: precipitation of aluminium hydroxide and adsorption of cadmium, lead and zinc ions onto floc particles of Al(OH)(3). Setting and leaching tests on cementitious mixes prove that the hazardous sludge produced from wastewater treatment can be completely mixed with washed fly ash and this mixture can be incorporated into cementitious matrices to a great extent (75 wt.% of total solid) without the risks of an unacceptable delay of cement setting and an excessive heavy metals leachability from solidified products. The better performance of the combined washing-immobilisation process as compared to the immobilisation process of unwashed fly ash may be ascribed primarily to the ability of the washing step in promoting the formation of hydrate phases that incorporate and/or convert heavy metal compounds into less reactive forms and, secondarily, to its ability of removing significant amounts of alkali chlorides and sulphates from fly ash. As a result, MSWI fly ash is transformed into a material that adversely affects cement hydration to a much lower extent than unwashed fly ash.     

Determination of solid waste sorption capacity for selected heavy metals in landfills

The adsorption process is largely a surface-action phenomenon. In this study, sorption capacities for heavy metals on a solid waste matrix were investigated. Five heavy metals (iron, copper, zinc, nickel and cadmium) were chosen because of their availability in any landfill site. The conditions during all the experimental runs were pH 7.0, temperature 32 degrees C and suppressed microbial degradation. For adsorption isotherm (Freundlich and Langmuir) calculations, fixed quantities of heavy metal ions were mixed with variable quantities of solid waste. The ratio of mass of adsorbate per unit mass of adsorbent was changed five times, by changing only the adsorbent amount. The results showed that the time required to reach equilibrium varied from metal to metal but all reached equilibrium within the first 32 h. The relative potential of sorption of the individual metals and mixed metals on the solid waste matrix is Fe > Zn > Cu > Ni > Cd. The sorption capacity of domestic solid waste matrix for heavy metals is quite significant and this property might prove helpful for the in situ removal of heavy metals in landfill operation.     

The effect of flow-through leaching on the diffusivity of heavy metals in stabilized/solidified wastes

The flow-through leaching test is a test method employed to study the leaching behavior of monolithic stabilized/solidified (S/S) hazardous wastes under the condition that the leachate flows through the sample. This method simulates the leaching process of the S/S hazardous waste disposed under a particular landfill condition when the S/S waste is more permeable than its surrounding materials or when the deterioration of the solidified waste form has reached a state that ground water can flow-through the waste via the porosity system of the S/S waste matrix.This paper describes a study on the long-term performance of the cement-based S/S heavy metal wastes using a flow-through leaching test method. Two series of leaching tests with different synthetic heavy metal waste samples were carried out. The S/S samples were made from five types of heavy metals with two kinds of binders. The metals were Pb(2+), Zn(2+), Cu(2+), Ni(2+) (positive ions as nitrates), and Cr(6+) (a negative ion as potassium dichromate), and the binders were type I ordinary portland cement (OPC) and pulverised fuel ash (PFA).The model developed by Godbee and Joy for simulating the leaching behavior was modified to estimate the diffusivity parameter in this study. The results obtained indicate that since the matrix of the solidified waste in a flow-through leaching tests is always being degraded, the values of diffusivities increase continuously during the leaching period. The diffusivity variation range was from 10(-13) to 10(-3)cm(2)/s, and were normally higher than those obtained from other test methods such as ANS 16.1 test and other dynamic leaching tests.     

The distribution of heavy metals during fluidized bed combustion of sludge (FBSC)

During combustion of wastewater treatment sludge, the inorganic constituents are converted into ash which contains the major fraction of the heavy metals present. The behaviour of heavy metals in combustion processes has been studied extensively for mostly coal combustion and waste incineration. For biomass and sludge, literature data are scarce and mostly limited to laboratory experiments. The present paper assesses the partitioning of eight heavy metals (Hg, As, Cd, Cu, Pb, Cr, Ni and Zn) in the different residues from a large-scale fluidized bed sludge combustor of 4.4 m i.d. The origin of the sludge is mostly from treating urban wastewaters (>90%), although some mixed sludge (urban+industrial, <10%) is also burnt. The different residues (bottom ash, fly ash, filter cake, scrubber effluent and stack emissions) were sampled and analysed during 33 weeks, spread over a period of 1 year. The mass balance of relevant heavy metals closes for 96.5%, inaccuracies being related to the unsteadiness of the process, the accuracy of the mass flow data monitored at the plant, and on collecting representative samples. It is also shown that all heavy metals under scrutiny, except Hg, are concentrated in the fly ash as collected in the electrostatic precipitator.     

A study on the chemical and mineralogical characterization of MSWI fly ash using a sequential extraction procedure

The presence of heavy metals in municipal solid waste incineration (MSWI) fly ash is of environmental concern due to their leaching potential in landfill environments. Sequential chemical extraction was performed on fly ash samples from a large-scale municipal solid waste incineration plant in East China. The transformation of the mineralogical species of fly ash during the sequential extraction was studied using X-ray fluorescence (XRF) and X-ray powder diffraction (XRD). The leaching behavior of heavy metals such as zinc, lead, cadmium and copper in MSWI fly ash was considered to have a dependency relationship with the components of calcium, such as aphthitalite, calcite, anhydrite and calcium aluminate or calcium aluminosilicate.     

Pollutants in incineration flue gas

Previous studies have shown that pollutants from incineration include heavy metals, organic compounds, particulate and acid gas. However, most studies on a single pollutant, it is rare for a study to concentrate on all possible pollutants and the relations between these pollutants under various incineration conditions. The objective of this work was to experimentally study the effect of different operating conditions on the pollutants emitted during incineration and the relations between these pollutants. The operating conditions of the experiments included the temperature of the combustion chamber and the species of organics. The findings indicated that the concentration of hydrogen chloride (HCl) in the presence of polyvinyl chloride (PVC) was higher than that of sodium chloride (NaCl). Regardless of what Cl-containing feedstock was added, the concentration of chromium (Cr) was constant. When organic chloride was added, Cr was the main metallic element which influenced the formation of polycyclic aromatic hydrocarbons (PAHs). On the other hand, when inorganic chloride (NaCl) was added, lead (Pb) was the major element.