Ash Landfill Research Articles

Alkaline bioleaching of municipal solid waste incineration fly ash by autochthonous extremophiles

The increasing demand for energy and the generation of solid waste have caused an alarming rise in fly ash production globally. Since heavy metals continue to be in demand for the production of materials, resource recovery from the recycling of these wastes has the potential to delay the depletion of natural ores. The use of microorganisms for the leaching of metals, in a process called bioleaching, is an eco-friendly and economical way to treat the metal-laden wastes. Bioleaching of fly ash is challenging due largely to the alkaline nature and toxic levels of heavy metals which are detrimental to microbial growth and bioleaching activity. The present work reports the isolation of indigenous bacteria from a local fly ash landfill site and their bioleaching performance. 38 autochthonous strains of bacteria were isolated from eight samples collected and plated on five different media. 18 of the isolates showed bioleaching potential, with significant alkaline pH or fly ash tolerance. Genetic characterization of the strains revealed a dominance of Firmicutes, with Alkalibacterium sp. TRTYP6 showing highest fly ash tolerance of up to 20% w/v fly ash, and growth over a pH range 8–12.5. The organism selectively recovered about 52% Cu from the waste. To the best of our knowledge, this is the first time a study on bioleaching with extreme alkaliphiles is reported.

Effect of Coal Fly Ash Leachate on the Bioluminescence Intensity of Vibrio fischeri

Coal fly ash is a residue of coal-fired thermoelectric power plants (TPPs) and is mostly dumped in ash ponds or landfill sites, even though it potentially contains significant amounts of water-soluble hazardous contaminants. Bioassay using the bioluminescent bacterium *Vibrio fischeri* is known to be applicable for assessing the short-term and sublethal toxicity of complex mixtures without the need for precise chemical characterization. However, this type of bioassay is potentially adversely influenced by the pH-induced protein denaturation of cells. Because coal fly ash leachates often have alkaline or acidic properties, when applying the *V. fischeri*-based bioassay to the samples, we need to know potential effect of the leachates on the bioluminescence of the bacteria. This study accordingly aimed to investigate the feasibility of applying the *V. fischeri* bioassay to coal fly ash leachate as a screening method. Fly ash samples were collected from 12 TPPs located in three East European countries: Bulgaria, Greece, and Serbia. The fly ash samples were prepared in sterilized distilled water by ultrasonic extraction and filtration using 0.45-MGRmPHI membrane filters. The filtrates were then mixed with a solution of the test bacterium. The bioluminescence intensity was measured using a luminometer. The results showed the ostensible influence of pH on bioluminescence intensity pronounced when following the typical protocol using a 5.0-g/L solid:liquid ratio. Accordingly, the pH of water extracts should be adjusted to within a range of 6 to 9 by dilution to observe the inhibition of bioluminescence by coal fly ash leachate as the objective endpoint.

Systematic Approach to Identifying Economically Feasible and Environmentally Benign Methods of Recycling Ash on a Regional Scale

This study systematically assessed and compared four ash recycling possibilities, namely forest fertilization, landfill construction, road construction, and road stabilization through the use of cost-benefit analysis and life cycle assessment methods. The results indicated that forest fertilization with ash was the most economically attractive method with a 60% increase in the net present value compared to ash landfilling, while reducing the environmental impact by 0.3%. On the contrary, road construction with ash resulted in a 13% reduction in the environmental impact and an increase in net present value of 25%. Landfill construction with ash was overall the least attractive proposition.

Uptake of metals and metalloids by Conyza canadensis L. from a thermoelectric power plant landfill

Fourteen metals and metalloids were determined in Conyza canadensis L. harvested from the fly ash landfill of the thermoelectric power plant ?Kolubara? (Serbia). Fly ash samples were collected together with the plant samples and subjected to sequential extraction according to the three-step sequential extraction scheme proposed by the Community Bureau of Reference (BCR; now the Standards, Measurements and Testing Program). The contents of metals and metalloids were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) in plant root and the aboveground part and correlated with their contents in the fly ash samples. The bioconcentration factor (BCF) and translocation factors (TF) were calculated to access uptake of metals from fly ash and their translocation to the aboveground part. Results regarding As revealed that fly ash samples in the proximity of the active cassette had higher amounts of the element. Principal component analysis (PCA) showed that As had no impact on the classification of plant parts. BCF for As ranged from 1.44 to 23.8 and varied, depending on the investigated area; TF for As ranged from 0.43 to 2.61, indicating that the plant translocated As from root to shoot. In addition to As, Conyza canadensis L. exhibited efficient uptake of other metals from fly ash. According to the calculated BCF and TF, the plant retained Al, Fe and Cr in the root and translocated Zn, Cd, Cu and As from root to shoot in the course of the detoxifying process.

The Composition and Use Value of Tree Biomass Ash

Abstract Wood-based ash landfilling is increasing issue not only in Latvia but in the whole world as more biomass is used for energy production. Utilization of wood burning waste as fertilizer is already used worldwide, but there is lack of information about chemical composition of wood ash obtained from Latvia plants, so the aim of this study was to determine chemical composition and analyse possible utilization options of wood-based ash from Latvia plants. Therefore wood ash samples from 53 companies were collected, sieved and chemical composition of samples was determined. It was concluded that within higher capacity of furnace more coarse fraction of wood ash was observed which is less valuable as fertilizer. Wood ash is good liming material consisting alkali compounds and other biogenic elements but also heavy metals, which are pollutants and could cause environmental problems.

Characteristics of ferrospheres in fly ashes derived from Bokaro and Jharia (Jharkand, India) coals

Coal burning power plants in the state of Jharkand, India, are facing the problem of fly ash landfilling and their economic and environmental impact. However, fly ash may be used in civil engineering constructions, including as geoliners for municipal wastes landfilling, however in this case the groundwater contamination should be taken in consideration.In this work a combination of analytical techniques is used to study the nature, composition and potential environmental impact of Fe-bearing morphotypes (ferrospheres) in fly ash from thermal power plants fed with coals from Bokaro and Jharia coalfields (Jharkand, India).The results show that the feed coals are sulfur-poor and ash-rich, dominated by quartz, clays and minor portions of Fe-bearing carbonates, such as siderite. Pyrite was not identified. Although iron is present in the fly ashes in significant proportions (from 2.7wt.% to 4.5wt.%), equivalent to an Fe2O3 content ranging from 3.5wt.% to 5.8wt.%, mineral phases such as magnetite and hematite are only present in minor proportions, or below detection limits of the XRD analyses. Iron in the ferrospheres occurs as massive or dendritic crystals, or as finely dispersed crystals trapped inside a glassy aluminosilicate matrix resulting from the release of iron oxide plumes into the aluminosilicate melt. In addition to these phases, iron also occurs as a component of the glass that makes up most of the fly ash materials. Finally, the contaminant potential of groundwater by the fly ash iron is negligible.

Selective Copper Bioleaching by Pure and Mixed Cultures of Alkaliphilic Bacteria Isolated from a Fly Ash Landfill Site

With the gradual depletion of high-grade copper ore deposits, secondary wastes are gaining importance as a source for metal recovery. However, the alkalinity and low copper concentration in some of these resources underscore the need for selective leaching agents. In this work, indigenous alkaliphiles from a fly ash landfill site with inherent pH tolerance, metal tolerance and copper leaching capability were isolated and investigated. Four isolates, namely Agromyces aurantiacus TRTYP3, Alkalibacterium pelagium TRTYP5, Alkalibacterium sp. TRTYP6 and Bacillus foraminis TRTYP17, each selectively leached about 50 % copper from 1 % (w/v) of fly ash. Mixed culture of these bacteria resulted in higher leaching of copper. The optimal combination was TRTYP3, TRTYP5, TRTYP6 and TRTYP17 in the ratio 1:1:3:1, which leached 88, 81, 78, 76, 70 and 55 % Cu from 1, 2.5, 5, 10, 15 and 20 % (w/v) of fly ash. While Cu and Pb were bioleached into solution, Fe and Zn were precipitated.

Assessment of heavy metals and rheological characteristics of coal ash samples in presence of some selective additives

The huge quantity of coal ash produced in Indian thermal power plants is disposed of in ash landfills or ash ponds. The deposition of ash in ash ponds through conventional lean slurry form is viewed as a major potential release of many environmentally sensitive heavy metals due to possible contamination with ground water. An attempt has been made in this paper to assess the leachability of the heavy metals such as Cu, Pb, Ni, Co, Zn, Cd, Hg and As from two Indian power plant ash samples in the presence of some selective low-cost additives. The additives used for the study were sodium silicate (Na2SiO3·5H2O), Reetha fruit (botanical name: Sapindus Mukorossi) extract, banana leaf extract, Aloe vera juice and active carbon. By adopting short duration (7 days) batch leaching test and toxicity characteristics leaching procedure (TCLP), the behaviour of various heavy metal ions released in water influenced by small dosage of these selective additives has been analysed. By introducing the same additives, the rheological behaviour of the two fly ash samples at high solids concentration (C W = 55–67.5 % by weight) was carried out using a HAAKE rotational rheometer (model: RheoStress 1, Thermo Fisher Scientific). The influence of small dosage of these additives on rheological parameters of the ash-water slurry has been discussed.

Assessment of PM10 pollution level and required source emission reduction in Belgrade area

The aim of this study was to assess PM10 pollution level and estimate required source emission reduction in Belgrade area, the second largest urban center in the Balkans. Daily mass concentrations and trace metal content (As, Cd, Cr, Mn, Ni, Pb) of PM10 were evaluated for three air quality monitoring sites of different types: urban-traffic (Slavija), suburban (Lazarevac) and rural (Grabovac) under the industrial influence, during the period of 2012–13. Noncompliance with current Air Quality Standards (AQS) was noticeable: annual means were higher than AQS at Slavija and Lazarevac, and daily frequency threshold was exceeded at all three locations. Annual means of As at Lazarevac were about four times higher than the target concentration, which could be attributed to the proximity of coal-fired power plants, and dust resuspension from coal basin and nearby ash landfills. Additionally, levels of Ni and Cr were significantly higher than in other European cities. Carcinogenic health risk of inhabitants' exposure to trace metals was assessed as well. Cumulative cancer risk exceeded the upper limit of acceptable US EPA range at two sites, with Cr and As as the major contributors. To estimate source emission reduction, required to meet AQS, lognormal, Weibull and Pearson 5 probability distribution, functions (PDF) were used to fit daily PM10 concentrations. Based on the rollback equation and best fitting PDF, estimated reduction was within the range of 28–98%. Finally, the required reduction obtained using two-parameter exponential distribution suggested that risks associated to accidental releases of pollutants should be of greater concern.

The spontaneous development of understory vegetation on reclaimed and afforested post-mine excavation filled with fly ash

We studied the spontaneous development of understory vegetation in a reclaimed fly ash landfill. Plots were reclaimed 11years earlier with sewage sludge, and boulder clay mixed with fly ash, and then afforested. Additionally, fertilisation with different doses of NPK was used. The treatments resulted in differences in the success of afforestation and in the spontaneous development of understory vegetation. Fifty-five understory species were found in total across all treatments. Nearly half of these species consisted of synanthropic vegetation, 20% represented meadow species, and 20% forest species. Sparse vegetation developed on raw fly ash without fertilisation and on plots shaded by tall trees. The most abundant understory vegetation was linked with the presence of two expansive grasses. Calamagrostis epigejos invaded plots with NPK-fertilised fly ash. Elymus repens, in part growing together with Galium aparine, developed dense stands in plots with fly ash covered with sewage sludge. The abundant growth of both grasses caused a significant reduction in understory species diversity. Canonical correspondence analysis (CCA) showed that the addition of sewage sludge and boulder clay had a stronger influence on understory species composition than fertilisation or shade from the tree canopy. The results of this study indicate that spontaneous succession combined with the technical reclamation measures and afforestation may be advantageous for the development of dense and relatively species-rich vegetation on fly ash landfills.

Environmental risks and problems of the optimal management of an oil shale semi-coke and ash landfill in Kohtla-Järve, Estonia

The main wastes of the Estonian shale oil industry – oil shale semi-coke and ashes – are deposited in landfills. The Kohtla-Järve oil shale semi-coke and ash landfill, which is likely the largest of its kind in the World, was started in 1938. The environmental risks connected with the landfill were assessed and prioritized. The most significant hazard to human health is emission of harmful landfill gases and the water contamination in the local river network is harmful for aqueous organisms. The spatial expansion of subsurface contamination predicted by the groundwater transport model completed is practically insignificant from the viewpoint of health services. The landfill's leachates must be captured and purified, and the closed part of the landfill should be covered by greenery. The partial landfill capping recently executed is useless. The EU Landfill Directive requirements imposed on the hydraulic resistance of geological barriers cannot prevent the leakage of contaminants from a landfill.

Phytoextraction of metals by Erigeron canadensis L. from fly ash landfill of power plant "Kolubara".

The objectives of this study were to determine the concentrations of Pb, Cd, As, Cr, Cu, Co, Ni, Zn, Ba, Fe, Al and Ag in Erigeron canadensis L. growing on fly ash landfill of power plant "Kolubara", Serbia. The content of each element was determined in every part of plant separately (root, stalk and inflorescence) and correlated with the content of elements in each phase of sequential extraction of fly ash. In order to ambiguously select the factors that are able to decidedly characterize the particular part of plant, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed. The bioconcentration factors and translocation factors for each metal were calculated in order to determine the feasibility of the use of plant E. canadensis L. for phytoremediation purpose. There were strong positive correlations between metals in every part of plant samples, and metals from pseudo total form of sequential extraction indicate that the bioavailability of elements in fly ash is similarly correlated with total form. Retained Al, Fe, Cr and Co in the root indicate its suitability for phytostabilization. This plant takes up Cd and Zn from the soil (bioconcentration factors (BCFs) greater than 1), transporting them through the stalk into the inflorescence (translocation factors (TFs) higher than 1). Regarding its dominance in vegetation cover and abundance, E. canadensis L. can be considered adequate for phytoextraction of Cd and Zn from coal ash landfills at Kolubara.

Physical and geochemical soil characteristics for remediation the ash landfill of the open pit Gracanica

This study relating to determining the physical and geochemical properties of the soil that will be used in the process of remediation the ash landfill of TPP Gacko in the internal landfill of the open pit Gracanica - Ash landfill. According to the Regulation on categories, testing and classification of waste (Official Gazette of RS, No. 56/10), the ash and slag belong to the landfill of no hazardous waste. Two samples were taken from the soil profile A-A from depth of 30 cm. The results of analysis of physical soil properties (primarily particle size distribution) and geochemical analysis (samples D1 and D2) meet or they are in the optimal limits for use in remediation.

Shale Stone and Fly Ash Landfill Use in Landslide Hazardous Area in Sirnak City with Foam Concrete

Sirnak City and the surrounding areas are on steeper slopes. There are sliding large land masses or rocks. Underground water and harsh climatic conditions contain high risk hazard areas in urban living site with higher population density. In order to eliminate landslides and related events, significant precautions should be taken. The mapping of landslide risk may ease to take precautions. Even the application of landfill rock may reduce water content of soil. In this research, fly ash and Mine Waste shale stone were used with low density foam concrete. Waste mixture at certain proportions decreased cement use. Shale stone as fine aggregate instead of fly ash in specific proportions improved mechanical strength and porosity. Hence landslide hazardous area could be safer for urban living.

Application the software packages Gemcom and Minex for design the waste landfill: An example of construction the cassette III phase 3 of ash and slag landfill of the thermal Power Plant Gacko

The world mining companies for design of mining facilities and with the aim of rational and costeffective solutions use the modern computer programs. Among the leading programs in this field are Gemcom and Minex. These software packages are not designed for design of landfills, but with certain knowledge and skills can also be used for this purposes with great success. This paper describes the design phase of 3 cassettes III ash and slag landfills of the Mine and Power Plant ''Gacko'', using the above software. Construction of ash and slag landfill was made using the 3D model in the program Gemcom 6.2, and calculation the amounts of material for preparation works and landfill capacity were calculated in the program Minex 5.2, in accordance with the applicable standards and legislation for these kinds of material. It is important to note that the positive experience gained in designing of ash landfill can be successfully applied also to the other waste materials, such as primarily materials incurred by hydrometallurgical processes of recycling the flotation tailings and disposed overburden material.

Extraction Characteristics of Selenium as Affected by Coal Fly Ash Type, Water Extractant, and Extraction Time

Selenium (Se) contamination can be a potential groundwater concern near un-lined coal ash landfills. Of all the Environmental Protection Agency’s priority and non-priority pollutants, Se has the narrowest concentration range considered beneficial and detrimental for aquatic and terrestrial organisms. The effects of ash type (i.e., fresh and weathered), water-extractant type (i.e., deionized water, rainwater, and groundwater), and extraction time (i.e., 2 and 6 hours) on Se, arsenic (As), and chromium (Cr) concentrations were investigated from Class C, subbituminous coal fly ash produced at the Flint Creek Power Plant (Benton County, AR). Water-extractable Se concentrations differed (p = 0.03) between ash types across water-extractants, but were unaffected (p > 0.05) by extraction times. Unexpectedly, fresh ash water-extractable Se concentrations were below minimum detection limits (i.e., 2.0 μg·L-1) for all treatments. In contrast, averaged over extraction times, the water-extractable Se concentration from weathered ash was greatest (p < 0.05) with groundwater and rainwater, which did not differ and averaged 60.0 μg·L-1, compared to extraction with deionized water (57.6 μg·L-1). Selenite SeO32- was greater (p < 0.001) in the fresh (3.85 mg·L-1) than in the weathered ash (0.70 mg·kg-1), while selenate SeO42- concentration was greater (p < 0.001) in the weathered (0.67 mg·kg-1) than in fresh ash (0.48 mg·kg-1). Results from this study indicate that environmental weathering of Class C, subbituminous fly ash promotes oxidation of selenite, to the less toxic, but highly mobile selenate. The formation of hydrated ettringite [Ca6Al2(SO4)3(OH)12·26H2O] and calcium selenite (CaSeO3) likely acted as a sink for weathered ash selenite. Implications of this research include a better understanding of the past, present, and future environmental and health risk potential associated with the release of watersoluble Se, As, and Cr to aid in the development of sustainable fly ash management strategies.

Biosorption performance, combustion behavior, and leaching characteristics of olive solid waste during the removal of copper and nickel from aqueous solutions

Several researchers have proved that agricultural by-products constitute good adsorbents for removing heavy metals from aqueous solution. However, few investigations have identified efficient strategies for the adsorbent′s regeneration. Hence, a global methodology for the removal of copper and nickel metals from wastewater including metal biosorption, thermal treatment and residual ash landfill is proposed. In order to validate this strategy, olive solid waste (OSW), provided by an olive oil mill from Tunisia, were used to remove copper and nickel on batch experiments. Copper and nickel were adsorbed on a monolayer of OSW surface with maximal adsorption capacity (q max) of 3.6 and 1.7 mg g−1, respectively. Contaminated OSW with copper and nickel were combusted at 850 °C in an electrical furnace. About 96 % of each metal was recovered in residual ashes that present a good secondary raw material for copper and nickel production. Low leaching transfers (≤4 %) were observed for copper and nickel from residual ashes leading to the possibility to be landfilled. Therefore, the suggested process can be used as an alternative to the classical technologies for effluent decontamination.

Soil attenuation of As(III, V) and Se(IV, VI) seepage potential at ash disposal facilities

Leachate from ash landfills is frequently enriched with As and Se but their off-site movement is not well understood. The attenuation potential of As and Se by soils surrounding selected landfills during leachate seepage was investigated in laboratory column studies using simulated ash leachate. As(III, V) and Se(IV, VI) concentrations as well as pH, flow rate, and a tracer were monitored in influent and effluent for up to 800 pore volumes followed by sequential desorption, extraction, and digestion of column segments. Column breakthrough curves (BTCs) were compared to predictions based on previously measured sorption isotherms. Early As(V) breakthrough and retarded As(III) breakthrough relative to predicted BTCs are indicative of oxidative transformation during seepage. For Se(VI), which exhibits linear sorption and the lowest sorption propensity, measured BTCs were predicted fairly well by equilibrium sorption isotherms, except for the early arrival of Se(IV) in one site soil, which in part, may be due to higher column pH values compared to batch isotherms. Most of the As and Se retained by soils during leaching was found to be strongly sorbed (60–90%) or irreversibly bound (10–40%) with <5% readily desorbable. Redox potential favoring transformation to the more sorptive valence states of As(V) and Se(IV) will invoke additional attenuation beyond equilibrium sorption-based predictions. With the exception of Se(IV) on one site soil, results indicate that attenuation by down-gradient soils of As and Se in ash landfill seepage will often be no less than what is predicted by equilibrium sorption capacity with further attenuation expected due to favorable redox transformation processes, thus mitigating contaminant plumes and associated risks.

Fly ash from coal combustion – An environmental source of organic compounds

The fly ash resulting from coal combustion (anthracite A coal type) for power generation was investigated. The fly ash produced during the coal combustion was emplaced in surface landfills near the thermal power plant facilities. A total of six samples were collected in the fly ash landfills which were therefore analyzed for their geochemical characterization. The analysis comprised the determination of total organic carbon and total sulfur, the identification of aliphatic hydrocarbons, and the identification and quantification of the sixteen priority polycyclic aromatic hydrocarbons (PAHs). This study provides information about the potential environmental impacts associated with the disposal of fly ash and, in addition, it also provides scientific knowledge about the effects of combustion process in the soluble fraction of coal organic matter and about the behavior of these compounds during combustion. The results about the aliphatic compounds demonstrated that the long-chain n-alkanes, the pentacyclic terpanes, and the regular steranes (C-27, C-28, C-29) increase in fly ash samples comparatively to coal. The PAHs with two and three aromatic rings (low molecular weight PAHs – LMW PAHs) were not detected in fly ash while fluoranthene (four rings) was detected in all samples, and benzo[a]anthracene (four rings), benzo[b]fluoranthene (four rings), indeno[123-cd]pyrene (five rings), benzo[ghi]perylene (five rings), and dibenzo[ah]anthracene (six rings) were detected in some of the samples. The absence of LMW PAHs and the presence of some high molecular weight (HMW) PAHs, with four to six rings, are attributed to the combustion process. The low sum of the priority PAHs in fly ash samples can be related with both, the high rank of the coal burned in the thermal power plant (anthracite A), with the technical combustion conditions and/or leaching process in the fly ash landfills. The organic compounds adsorbed in fly ash particles may be released into the environment and therefore can represent a potential source of contamination of soils and waters and human health problems.

Importance of irrigation and plant size in the establishment success of different native species in a degraded ecosystem of central Chile

Irrigation has frequently been considered a necessary step in reforesting open areas of semiarid ecosystems. However, the success of irrigation has mainly been assessed using young and small plants, typically younger than two years old. Few studies have explored whether irrigation is also important with older and larger plants, and if the use of larger plants may enhance reforestation success. We tested the effect of irrigation and plant size on survival and height growth of six tree species from the Mediterranean region of Chile, for planting on a reclaimed fly ash landfill lacking woody vegetation. Between 2008 and 2010 we planted and monitored 160 plants of each species in a factorial design including 1- and 4-year-old trees (smaller and larger, respectively), with and without irrigation. Irrigation improved survival in more water-demanding species regardless of plant size, and primarily among smaller plants for species classified in the middle of a water requirement gradient. With more drought-resistant species, irrigation was not important for survival. The use of larger plants enhanced survival but not growth, and mainly in more water-demanding species. In general, height growth for some species was higher with irrigation and mainly among smaller plants.