Fly Ash Dumps Research Articles

Microbe-induced changes in metal extractability from fly ash

A low cost and eco-friendly technology to bioremediate toxic metals associated with fly ash dumps that contaminate ground and surface water in and around fly ash settling ponds, was investigated. The impact of augmentation of fly ash tolerant bacterial strains, isolated from Typha latifolia growing naturally on fly ash dumps, was studied for metal extractability. It was observed that most of the bacterial strains either induced the bioavailability of Fe, Zn and Ni or immobilized Pb, Cr, Cu, Cd in the fly ash. However, there were few exceptions also. In case of Ni, eight strains enhanced metal mobility, while others caused metal immobilization. The findings also suggest that metal solublization and immobilization are specific to bacterial strains. While induced bioavailability of metals by bacteria may be used to accelerate the phytoextraction of metals from fly ash by hyper accumulator plants, immobilization of metals can check their migration to water reservoirs and reduce the human suffering in affected areas. Thus, bacteria serve the dual purpose and may result in the microbe- assisted phytoremediation of contaminated sites.

Restoration of fly ash dump through biological interventions

Field experiment on 10 ha area of fly ash dump was conducted to restore and revegetate it using biological interventions, which involves use of organic amendment, selection of suitable plant species along with specialized nitrogen fixing strains of biofertilizer. The results of the study indicated that amendment with farm yard manure at 50 t/ha improved the physical properties of fly ash such as maximum water holding capacity from 40.0 to 62.42% while porosity improved from 56.78 to 58.45%. The nitrogen content was increased by 4.5 times due to addition of nitrogen fixing strains of Bradyrhizobium and Azotobacter species, while phosphate content was increased by 10.0 times due to addition of VAM, which helps in phosphate immobilization. Due to biofertilizer inoculation different microbial groups such as Rhizobium, Azotobacter and VAM spores, which were practically absent in fly ash improved to 7.1 x 10(7), 9.2 x 10(7) CFU/g and 35 VAM spores/10 g of fly ash, respectively. Inoculation of biofertilizer and application of FYM helped in reducing the toxicity of heavy metals such as cadmium, copper, nickel and lead which were reduced by 25, 46, 48 and 47%, respectively, due to the increased organic matter content in the fly ash which complexes the heavy metals thereby decreasing the toxicity of metals. Amendment of fly ash with FYM and biofertilizer helped in profuse root development showing 15 times higher growth in Dendrocalamus strictus plant as compared to the control. Thus amendment and biofertilizer application provided better supportive material for anchorage and growth of the plant.

Evaluation of metal mobility/immobility in fly ash induced by bacterial strains isolated from the rhizospheric zone of Typha latifolia growing on fly ash dumps

In this investigation, 11 bacterial strains were isolated from the rhizospheric zone of Typha latifolia. All the strains were aerobic, showed positive result with indole production and were able to grow in MacConkey agar. However, four strains were gram positive and others gram negative. These strains were inoculated separately in the fly ash with additional source of carbon to test their ability to increase the bioavailability or immobilization of toxic metals like Cu, Zn, Pb, Cd and Mn. It was observed that most of the bacterial strains either enhanced the mobility of Zn, Fe and Mn or immobilized Cu and Cd. However, there were a few exceptions. For example, in contrast to other bacterial strains, NBRFT6 enhanced immobility of Zn and Fe and NBRFT2 of Mn. On the other hand, in place of immobility induced by most of the bacterial strains, NBRFT8 and NBRFT9 enhanced bioavailability of Cu. However, in case of Cd, all the strains without any exception immobilized this metal. The results also indicated that the mobility/immobility of trace metals from the exchangeable fractions was the specific function of bacterial strains depending upon the several edaphic and environmental factors. Based on the extractability of metals from fly ash, a consortium of high performer bacterial strains will be further used to enhance the phytoextraction of metals from fly ash by metal accumulating plants. On the other hand, bacterial strains responsible for immobilization of metals may be used for arresting their leaching to water bodies.

Pseudomonas delhiensis sp. nov., from a fly ash dumping site of a thermal power plant

A phenanthrene- and citronellol-degrading bacterium, strain RLD-1(T), was isolated from the fly ash dumping site of a thermal power plant in Delhi, India. The 16S rRNA gene sequence indicated that this strain belongs to the genus Pseudomonas; high levels of sequence similarity were found with respect to Pseudomonas citronellolis DSM 50332(T) (98.9 %), Pseudomonas jinjuensis DSM 16612(T) (97.6 %) and Pseudomonas nitroreducens DSM 14399(T) (97.5 %). Phylogenetic analysis based on 16S rRNA gene sequences placed the strain within the clade represented by these three strains. Strain RLD-1(T) showed low levels of DNA-DNA hybridization with respect to P. citronellolis DSM 50332(T) (36 %), P. jinjuensis DSM 16612(T) (4 %) and P. nitroreducens (13.7 %). Strain RLD-1(T) can also be distinguished from these three strains on the basis of several biochemical and physiological attributes. The novel strain contained high levels of cellular fatty acids 18 : 1omega7c, 16 : 0 and 16 : 1omega7c, along with 10 : 0 3-OH and 12 : 0 3-OH. Thus, strain RLD-1(T) represents a novel species of the genus Pseudomonas, for which the name Pseudomonas delhiensis sp. nov. is proposed. The type strain is RLD-1(T) (=MTCC 7601(T)=CCM 7361(T)).

Description of Sphingobium fuliginis sp. nov., a phenanthrene-degrading bacterium from a fly ash dumping site, and reclassification of Sphingomonas cloacae as Sphingobium cloacae comb. nov.

A phenanthrene-degrading bacterium, strain TKP(T), was isolated from a fly ash dumping site of the thermal power plant in Panki, Kanpur, India, by an enrichment culture method using phenanthrene as the sole source of carbon and energy. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain belonged to the genus Sphingobium, as it showed highest sequence similarity to Sphingobium herbicidovorans DSM 11019(T) (97.3 %) and Sphingomonas cloacae JCM 10874(T) (96.5 %), compared with only 91-93 % similarity to members of other genera such as Sphingomonas sensu stricto, Novosphingobium, Sphingopyxis and Sphingosinicella. In DNA-DNA hybridization experiments with strains that were closely related phylogenetically and in terms of 16S rRNA gene sequences, i.e. Sphingobium herbicidovorans DSM 11019(T) and Sphingomonas cloacae JCM 10874(T), strain TKP(T) showed less than 70 % relatedness. Strain TKP(T) contained sphingoglycolipids SGL-1 and SGL-2 and 18 : 1omega7c as the predominant fatty acid, with 16 : 0 as a minor component and 14 : 0 2-OH as the major 2-hydroxy fatty acid. Thus, phylogenetic analysis, DNA-DNA hybridization, fatty acid and polar lipid profiles and differences in physiological and morphological features from the most closely related members of the Sphingobium group showed that strain TKP(T) represents a distinct species of Sphingobium. The name Sphingobium fuliginis sp. nov. is proposed, with the type strain TKP(T) (=MTCC 7295(T)=CCM 7327(T)). Sphingomonas cloacae JCM 10874(T) formed a coherent cluster with members of Sphingobium, did not reduce nitrate to nitrite and had a fatty acid profile similar to those of Sphingobium species; hence Sphingomonas cloacae should be transferred to the genus Sphingobium as Sphingobium cloacae comb. nov., with the type strain JCM 10874(T) (=DSM 14926(T)).

Bioavailability of Metals in Fly Ash and Their Bioaccumulation in Naturally Occurring Vegetation: A Pilot Scale Study

A pilot scale study was conducted to find out the different forms of metals if fly ash (FA) and bioaccumulation of these metals in the naturally growing vegetation on FA dumps. The total, acid extractable, bioavailable and water soluble fraction of metals of Fe, Cu, Mn, Zn, Ni, Co and Pb, and their bioaccumulation coefficients (BAC) on naturally growing vegetation were determined. FA samples had a neutral pH, low electrical conductivity, low organic C and trace amounts of N and P. The relative abundance of total metals in FA were found in the order Fe >Mn >Zn >Ni >Co>Cu. The concentration of bioavailable (DTPA) metals depend on the type and nature of coal used in thermal power stations. In the water the extract solution, only Fe and Zn were found above detection limits. After one year only four species of naturally occurring herbaceous vegetation were found growing and Cynodon dactylon (grass) covered almost entire surface of the FA. Iron accumulated to the greatest extent in vegetation followed by Mn, Zn, Cu, Pb, Ni and Co. The sequence of BAC for different metals were Fe (202)>Mn(90)>Zn (63)>Pb(49)>Ni(41)>Cu(24). The experimental study revealed that Cynodon grass could be used for remediation of fly ash without any amendments, as this grass species act as metal excluder type.

Efficacy of various amendments for amelioration of fly-ash toxicity: growth performance and metal composition of Cassia siamea Lamk

Plants of Cassia siamea Lamk were grown in garden soil (control), fly-ash (100%) and fly-ash amended by various ameliorants (cowdung manure, press-mud, garden soil; 1:1, w/w). The plants survived in fly-ash (100%) though their growth was less in comparison to the treatments. Fly-ash + press-mud (1:1, w/w) proved to be the best combination as growth (total biomass, leaf number, photosynthetic area, total chlorophyll and protein) was significantly high in this treatment followed by cowdung manure and garden soil. Leaves and roots accumulated significant amount of Cu, Zn, Ni and and Fe. However, the concentration of all the metals was more in roots than leaves except Ni. Although, fly-ash contains high amount of metals but the metal uptake was more in the plants grown in fly-ash + press-mud mixture. Inspite of high metal availability in fly-ash and press-mud mixture, plant growth was good. This might be attributed to the some metal detoxification mechanism active in this treatment. The present study concluded that C. siamea seems to be a suitable plant for developing a vegetation cover on fly-ash dumps.

Modification of Soil Quality Near a Pulp and Paper Mill

The Nagaon Pulp and Paper Mill (Assam, India) produces 100,000 tonnes of paper annually from bamboo. The mill is surrounded by a vast spread of agricultural land on all sides excepting the southern side, which is covered with hills and deep forests. The present study was undertaken with a view to assess the impact of the paper mill operations on the quality of the surrounding soil. Surface soil samples (0–15 cm depth) were collected in both dry and wet seasons over a four-year period from 19 points at different distances from the mill. The soil quality was determined with respect to a large number of representative physico-chemical properties. Estimation of the major oxides, e.g., SiO2, Al2O3, Fe2O3, MnO, and TiO2 showed a preferential accumulation of Al2O3, Fe2O3, and MnO in soil near the mill due to the dumping of fly ash and other solid wastes in the surrounding low lying land. Definite directional trends were observed not only with respect to these oxides, but also with the metals Ca, Mg, Na, and Pb, which decreased away from the mill. The soil pH had a tendency to turn alkaline near the mill owing to the discharge of highly alkaline effluent by the mill. The physical characteristics of the soil, viz., water holding capacity and bulk density increased with distance from the mill while the hydraulic conductivity had an opposite trend. N, P, K, B, Cl-, and organic C contents of the soil had shown a rapid decreasing trend away from the mill indicating that the dumping of solid waste and discharge of nutrient-rich treated effluent had contributed to raised levels of these constituents near the mill.

Leaching Studies of Inorganic and Organic Compounds from Fly Ash

Fly ash is produced in massive quantities by fossil fuel based power plants and waste incinerators, and contains high levels of potentially toxic chemicals. Various leaching tests exist to determine the available fractions, but the outcome is strongly dependent on the experimental conditions, and these have not yet been harmonised at the international level. In order to test existing protocols for heavy metals, several intercomparisons were organised within the framework of an EU-INCO project "ANALEACH", in which seven institutes from five countries participated. Two existing reference materials were made available for the project and test batches of two new fly ash reference materials were produced. Availability tests, leaching tests and pH-stat tests were studied and critical steps in the procedures were identified. Fly ashes can also contain large amounts of inorganic sulphur and nitrogen compounds, and the determination and leaching behaviour of these compounds were also studied. In one intercomparison for metals, inorganic S and N-compounds were also included. A five-step leaching test was optimised for fly ash in order to link metal fractions to different types of binding. Column leaching experiments were carried out to investigate leaching from fly ash into soil, mimicking the effects of (acid) rain on fly ash deposited on topsoil after atmospheric transport. The major fraction of the leached metal ions was retained by the soil. Also large numbers of organic compounds (including many toxic ones) were identified in fly ash extracts, especially in city waste incinerator ash. Leaching procedures based on ultrasonic extraction were developed for organic compounds and an intercomparison exercise was organised. In a field study at the river Nitra(Slovakia) numerous organic pollutants were found at elevated levels downstream from a major fly ash dump site.

Foliar Content of Phenolic Compounds in Platanthera bifolia from Natural and Transformed Ecosystems at Different Stages of Orchid Development

The representatives of the family Orchidaceae Juss. are often used as a source of natural antioxidants, including phenolic compounds, which play an important role in plant resistance under stressful conditions. This study investigates the content of lipid peroxidation products and soluble phenolic compounds in flowering plants of Platanthera bifolia (L.) Rich. growing in natural (forest park) and transformed (fly ash dumps of Thermal Power Stations) ecosystems of the Middle Urals, Russia, as well as the content of flavonoids at different stages of orchid development. Research has shown that in disturbed habitats, P. bifolia is capable of forming abundant populations containing a significant portion of the flowering plants. Additionally, flowering orchids from fly ash dumps contained an average 20 % more lipid peroxidation products, which indicated a shift in the redox balance towards oxidative processes. An increase by 2.4 times on average in the content of phenolic compounds, particularly flavonoids, was observed at all developmental stages of the plants growing in the transformed ecosystems. Regardless of the growing conditions, the non-flowering mature individuals were characterized by a minimum content of flavonoids, probably due to pre-generative metabolic restructuring. Yet, in the period of orchid blooming, the flavonoid content in their leaves increased again in all study sites. At the same time, the flavonoid proportion of the total soluble phenolic compounds was 42 % in the natural habitat, increasing to 66 % on average in the transformed ecosystems. Thus, flavonoids are involved in the protective adaptive responses of P. bifolia, not only ensuring the survival of this orchid but also contributing to the implementation of its ontogenetic program

Behavior of stabilized fly ashes in solid waste landfills

In Japan, the fly ash generated by incineration of municipal solid waste has come to be handled as general waste under special management in recent years. At the same time, direct landfilling or ocean dumping of fly ash is legally prohibited. To avoid the possibility of causing damages affecting human health or life environment, fly ash must be subjected to intermediate treatment, and must stabilized, encapsulated and made hygienic by removing pollutants. Four methods can be given for fly ash intermediate treatment; (1) cement solidification, (2) treatment by chemicals, (3) acid and other solvents and (4) melting and solidification. On the other hand, various phenomena affecting fly ash occur on the landfilled waste layer, such as generation of organic acid and carbon dioxide gas due to decomposition of solid waste. Fly ash solidified by cement is deteriorated by water-soluble sulfate and organic acid and carbon dioxide gas produced by decomposition of organic substances in the municipal solid waste. This may result in a reduced strength of hazardous substances and re-melting of fly ash solidified by cement. Furthermore, encapsulated hazardous heavy metals may be eluted from fly ash treated by chemicals due to the change in chemical environments (pH, ORP, etc.) in the landfilled solid waste layer according to stabilization of the landfilled solid waste. However, not much is known about the physical and chemical properties of the fly ash after it has been disposed of with the general solid waste at the landfill site. Thus, in this present study, the large-sized landfill model lysimeter is filled with cement-solidified fly ash or chemically treated fly ash treated together with municipal solid waste (bottom ash and shredded solid waste) to obtain correct information on the changes in the physical and chemical properties of the cement-solidified fly ash, and temporal concentration of hazardous substances (Pb, Cd, Cr 6+) contained in seepage leachate or leachate in the landfilled solid waste layer, thereby clarifying the long-term stability of the disposed fly ash. This study has revealed that the pH value of the cement-solidified fly ash tends to be neutralized with the process of time, although the compression strength of the cement-solidified fly ash left to stay in the landfilled solid waste for three years is not reduced much below that at the time of experiment start-up. This trend of neutralization has been found to be conspicuous in the vicinity of the leachate collection pipe at the bottom landfill layer. Furthermore, the pH values of seepage leachate and leachate have been observed to be reduced by the disposal of the fly ash chemically treated with municipal solid waste. This indicates that the concentration of the heavy metal such as Pb and Cd is severely affected by pH values. Namely, the pH value of the leachate from the large-sized landfill model lysimeter filled with chemically treated fly ash is close to neutral value, and concentrations of the Pb and Cd tend to be greater than those of the leachate from the large-sized landfill model lysimeter not filled with chemically treated fly ash. This suggests that the chemical properties of the treated fly ash and the solid waste disposed of with it determines the pH value of the seepage leachate and leachate and, at the same time, greatly affects the concentration of the heavy metal.

Application of scanning electron microscopy for pollution particle source determination in residential dust and soil

AbstractMany tons of electric furnace flue dust accumulated in an industrial area in Tifton, Georgia. Vehicles transporting the flue dust, classified as K061 hazardous waste because it contained lead and cadmium, initially dumped the material in a warehouse. Once the warehouse was full, the flue dust was dumped in uncovered piles. Run‐off from the piles and wind‐driven particles had the opportunity to contaminate nearby industries, residential buildings, and neighborhood soils over a period of many years. Scanning electron microscopy‐energy dispersive x‐ray spectrometry (SEM‐EDS) was used to compare the morphology and chemical composition of fly ash dust from the suspect pile with samples collected from the surrounding buildings and soil. Adhesive samplers were used to collect dust that had accumulated in buildings surrounding the fly ash dump site. Suspect dust particles were analyzed by SEM‐EDS and compared with known dust particles from the fly ash pile. Soil samples were dried, sieved, and the “fines” analyzed by SEM‐EDS for comparison with samples from the fly ash pile. Fly ash particles similar in morphology and chemical composition to the fly ash in the suspect pile were identified in most of the buildings sampled surrounding the fly ash dump site and in all of the soil samples analyzed surrounding the dumpsite. This case study illustrates the usefulness of applying morphology and chemistry information acquired by SEM‐EDS for pollution particle source determination.

Long‐term supply and uptake by plants of elements from coal fly ash

Abstract To assess the mineral composition of plants growing in pure fly ash, grasses growing on lysimeters filled with alkaline, neutral, or acid fly ash were sampled several times in a 6‐year period. The samples were analyzed for elements essential for plants and animals as well as non‐essential, but environmentally significant, trace elements. Grasses were also sampled from ash dumps that were 20 and 30 years old. Fly ash is not a proper source of plant macronutrients N, P, and K. Plant growth on the alkaline fly ash can be influenced for some time by the high salinity of that ash. Grasses growing on unweathered fly ash were found to be high in Al, B, Co, Fe, Mo, Ni, Pb, and Se. Concentrations of several elements declined in time but levels of B, Fe, Mo, and Ni were still elevated in grasses on both fly ash dumps. All concentrations, except Al, were lower than toxicity levels for plants as found in literature. In plants growing on fresh fly ash concentrations of Mo, Pb, and Se can exceed the maximum tolerable levels for domestic animals. On weathered fly ashes (ash dumps) the Mo, Pb, and Se concentrations in grasses were below the maximum tolerable levels. Effects on animals by Mo in weathered ash may not be excluded because Mo concentrations can be high enough to induce Cu deficiency. Animals that feed on plants grown on fly ash could suffer from Ca, Mg, Na, and P deficiency.

Chemical Aspects of Coal Fly Ash Disposal at Sea: Predicting and Monitoring Environmental Impact

Monitoring studies at a deep sea fly ash dumping site found that the ash accumulates at the sea bed, causing a physical change in the sediments. Partial leaching of cadmium and chromium to seawater was detected in laboratory experiments, but no evidence of it was found in the sediments or benthic fauna sampled at the dumping site.

Edaphological characteristics of unweathered and weathered fly ashes from Gondwana and lignite coal

Naturally weathered and unweathered samples of fly ashes produced from Gondwana and lignite coals were characterized for their edaphological properties. The particle size distribution in these fly ashes varied widely, and the percentage of <0·002 mm size particles governed their water holding capacity. All fly ashes were noncoherent in the dry state and had lower particle density than quartz and mulite. The fly ashes were low in available N, but were sufficient in available P, K, Ca, Mg, S, Cu, Fe, Mn, Zn and B. Among the fly ashes, unweathered lignite fly ash was the richest source of K, Ca, Mg, S and Fe, while weathered lignite fly ash had the highest amounts of Mn, Zn and B. The pH of the fly ashes was closely related to the ratio of exchangeable Ca to exchangeable Al. The fly ashes were high in soluble salt, but were poor in cation exchange capacity. As an amendment to correct soil pH, the fly ashes had a poor buffering capacity. Weathering decreased the total Fe, available S and exchangeable Na percentages, but increased the organic C content of the fly ashes. Invariably, an excess of soluble salts and exchangeable Na could limit plant growth on fly ash dumps. Toxic levels of B and Al existed in only some fly ashes.

Ocean Disposal of Consolidated Spray Dryer Flue Gas Desulfurization Wastes

Combustion of coal in electric power generating stations results in the production of large quantities of fly ash and flue gas desulfurization end products. These wastes must be disposed of by environmentally acceptable means. Ocean disposal of these wastes is an attractive option for power stations located on coastal waterways. Dumping of fly ash and untreated wet FGD sludge is environmentally deleterious. However, wet scrubber sludge stabilized with fly ash can be formed into solid dense blocks which have been shown to be acceptable for ocean disposal. The Marine Sciences Research Center has been investigating this disposal option for the past five years. A new FGD technology, Spray Drying Absorption, was introduced about five years ago. This process produces a dry end product composed of fly ash, desulfurization reaction products and excess reagents. When lime is the reagent the end products can be dampened and consolidated into self-hardening dense blocks. Niro Atomizer has been investigating dry FGD end product disposal and utilization for the past three years. An assessment of the feasibility of using solid blocks formed from dry FGD end products for ocean reef construction is being performed by the Marine Sciences Research Center. Consolidated dry FGD end products from Niro Atomizer's Riverside dry FGD demonstration facility and Copenhagen dry FGD pilot plants were tested. These wastes represent low sulfur western and European coal applications. The end products were dampened and consolidated into Proctor cylinders. After curing, the cylinders were exposed in sea water systems including the open seas for up to 6 months. Block structural integrity was maintained during this period and porosity remained essentually unchanged. The unconf ined compressive strength remained high during the test period.

Emanation of radon from fly-ash and gypsum

The emanation of radon from fly-ash and gypsum can be estimated from a simple model. The cases of a fly-ash dump and a room panelled with gypsum plates are considered.

Selenium in tissues of woodchucks inhabiting fly ash landfills

A coal-burning electric power generating plant, Milliken Station, is located in Lansing, New York, about 30 km north of Ithaca on the eastern shore of Cayuga Lake. Fly ash generated there is spread over a 6 hectare landfill site about 3 km east of the plant. The total selenium content of random samples of fly ash taken on the dump site ranged from 5 to 17 ppM. Woodchucks (Marmota monax) were live-trapped among vegetation growing on the landfill. During the same period, 25 woodchucks (control animals) were similarly trapped or shot in a number of locations 8 to 30 km from the fly ash dump. Trapped animals were asphyxiated with carbon dioxide and all animals were subjected to routine necropsy examination. Liver and lung tissues were taken for the determination of selenium. The fluorimetric method was used for selenium analysis. The recovery of 1 ppM of selenium from liver and lung tissue was 90 and 92%, respectively. The method was sensitive to about 0.01 ppM of selenium on a dry weight basis.

Selenium in pollen gathered by bees foraging on fly ash-grown plants.

Pollen collected from the rear legs of honey bees found foraging on asters voluntarily growing on a fly ash dump in Endwell, New York, was found to contain a high concentration of selenium. Pollen from bees foraging on asters growing on field soil contained no detectable selenium.