Fly Ash Dumps Research Articles

A comprehensive review on phytoremediation of fly ash and red mud: exploring environmental impacts and biotechnological innovations.

Fly ash (FA) and red mud (RM) are industrial byproducts generated by thermal power plants and the aluminum industry, respectively. The huge generation of FA and RM is a significant global issue, and finding a safe and sustainable disposal method remains a challenge. These dumps contain harmful trace elements that have a significant impact on the environment and human health. It contributes to air, water, and soil pollution, disrupting the delicate balance of the ecosystems. It also introduces toxins into the food chain through biomagnification. Utilizing a vegetation cover can assist in addressing environmental health concerns associated with FA and RM dumps. Nevertheless, the presence of alkaline pH, toxic metals, the absence of soil microbes, and the pozzolanic properties of both FA and RM pose challenges to plant growth. Taking a comprehensive approach to the ecological restoration of these dumps through phytoremediation is crucial. This review examines the role of various factors in the ecological restoration of FA and RM dumps, specifically the use of naturally occurring plants. However, the issue of slow plant growth due to a lack of nutrients and microbial activities is being resolved through various advances, such as amendments in conjunction with organic matter, microbial inoculants, and the use of genetically modified plants. Research has demonstrated the benefits of using amendments to stimulate vegetation growth on FA and RM dumps. In this review, we explore various approaches to restoring FA and RM dumps and transforming them into productive sites that enhance the ecosystem services.

Isolation and biochemical screening of Phosphate Solubilizing Bacteria from Kans grass rhizosphere of Fly Ash Dump Sites near NTPC, Angul

Soil bacteria, capable of converting insoluble phosphorus into soluble, plant-accessible forms, collectively known as phosphate-solubilizing bacteria (PSB), have emerged as an eco-friendly and cost-effective solution for supplying phosphorus to plants. This study presents preliminary insights into the rhizospheric bacterial population associated with the vigorously growing kans grass (Saccharum spontaneum L.) at different fly ash disposal sites of NTPC, Kaniha in Angul district, Odisha. In the quest for efficient plant growth promoting rhizobacteria (PGPR) strains with diverse beneficial activities, a total of sixteen bacterial isolates were collected from the rhizosphere of chosen plant species and identified, with only ten isolates underwent biochemical characterization. Among these, four isolates exhibiting a higher phosphate-solubilizing index were further characterized, serving as a foundation for future exploration of the bio-prospective potential of rhizosphere bacteria in this unique ecological niche. Further assessment of these isolates, showcasing several plant growth-promoting (PGP) traits, is essential to determine their efficacy as potent PGPR agents.

Carbon Sequestration by Soils of Ash Dump Forest Areas in the Middle Urals (Russia)

The purpose of this article was to assess the participation of young soils of ash dump forest communities in carbon sequestration by soils of southern taiga forests, considering the physico-chemical properties of the ash substrate and forest litter (pH, TOC, TN, content of P and K mobile compounds, and exchangeable Ca and Mg ions). It was revealed that on three Middle Ural ash dumps (composed of fly ash from various brown coals) over 50–60 years, forest communities spontaneously formed according to the zonal type (with the dominance of Betula pendula Roth and Populus tremula L.) with poorly differentiated young soils—technosols. For the first time, as a result of using an integrated approach to assess the direction of forest ecosystem formation on fly ash dumps, a tendency to increase carbon stocks in technogenic soils that have not reached the level of zonal soils was revealed, as well as the dependence of C accumulation on some physico-chemical characteristics of ash was established. Carbon stocks in Technosols are on average equal to 44 t/ha but vary significantly. It was shown that there is a medium negative relationship between the content and stocks of organic carbon in soils formed on a technogenic substrate and the content of mobile phosphorus compounds in them (the correlation coefficient is −0.58 and −0.53, respectively). The average carbon stocks in the litter of technosols, which is the main source of organic carbon in forest soils, are 3.2 t/ha. It was revealed that the carbon stocks in the litter are most influenced by the content of exchangeable calcium cations and magnesium in it (the correlation coefficients are −0.68 and −0.69, respectively). Any correlation between the studied litter parameters and carbon accumulation in the soils of ash dumps was found. The study revealed that the carbon stocks in the technosols of ash dump forest communities are two times less than the carbon stocks in the zonal forest soils of the Middle Ural southern taiga. The stocks of this element in the litter of young soils are equal to 1/3 of the litter of zonal soils. The composition of the humus substance system formed in the soils of forest areas of ash dumps and zonal soils is similar. The results of this study can serve to fill gaps in the knowledge about carbon sequestration by soils and aim to draw attention to forest communities of technogenic ecosystems to consider the contribution of their components to carbon sequestration.

Response surface method for optimization of process variables for bioaccumulation of metals with Jatropha curcas on fly ash-amended soil.

Heavy metal contamination is a serious rising issue with the dumping of fly ash (FA). A recent focus of researches and practices tends towards reutilization of FA with bioremediation technique using various plants. The present research aimed to investigate optimum metal extraction in fly ash-amended soil using microbes and treated wastewater with Jatropha curcas plant using response surface methodology (RSM). The Box-Behnken design was used to determine the optimum condition for maximum metal remediation with three levels and three variables, viz., fly ash percentage (5, 12.5, 20%), microbial dose (0.5, 5.25, 10ml), and contaminant level of water to irrigate the plant (freshwater, treated wastewater, untreated wastewater). The approach adopted was to set fly ash percentage as "maximum," microbial dose as "minimum," and contaminant level of water to irrigate the plant as "in range." The outcome of the present research provided the best prediction models, integrated the process variables, and developed rotational curves for analyzing metal remediation in 360° rotation for Fe, Mn, Zn, Cu, and Al as responses of interest. The optimum conditions for maximum bioremediation from fly ash-amended soils by bioaccumulation on Jatropha curcas plant worked out as 13.866% fly ash, 4.088ml microbial dose, and treated wastewater as type of water to irrigate the plant that bioaccumulated Fe, Mn, Zn, Cu, and Al as to 26.904, 0.760, 0.160, 0.162, and 12.895mg/l.

Multiple Site Dissimilarities of Herbaceous Species Due to Coal Fly Ash Dumping Based Soil Heavy Metal Toxication

The present study analyzes the determinants and patterns of the regional, local, and differential plant diversity of two different sites with similar climatic but varied edaphic factors. This research was undertaken to study the plant diversity and population structure as a consequence of variation in the soil quality between two biotopes: Guru Ghasidas Vishwavidyalaya in Koni (site-I) and National Thermal Power Corporation in Sipat (site-II). The soil of site-I was found to be fertile and showed rich vegetation. On the other hand, the soil of site II was found to be contaminated with heavy metals, which impacts the flora of the region. The ecology of both sites was studied, and their quantitative and qualitative aspects were compared and contrasted. The abundance, density, and richness of the plants in site II were fairly lower than in site-I, which was confirmed by utilizing Simpson's and Shannon's diversity indices. Many of the species collected from site II were heavy metal accumulators and could also serve as indicators of heavy metal toxicity.

Phenotypic Responses of Some Functional Traits in Four Native Perennial Grass Species Grown on Fly Ash Dump and Native Soil.

Functional response traits of four perennial grass species (Imperata cylindrica, Cenchrus ciliaris, Sporobolus diander, and Cynodon dactylon) growing on the fly ash dump and referral site having native soil were evaluated with the objective of selecting species suitable for rapid development of vegetation cover on the fly ash dumps. All the four species showed spectacular plastic responses in functional traits of plants grown on the fly ash dump and are induced by habitat and hence are adaptive. The traits associated with the root system such as root length, spread, the volume of the substratum occupied by the root system, and root biomass showed greater plasticity than the traits of the shoot system such as shoot biomass, the mean number of tillers per clump, and mean height of tillers. For instance, for all the grass species, the ratio of root/shoot biomass was higher for fly ash grown plants as compared to that of plants grown in native soil. The highest ratio was recorded for C. dactylon (5.61 ± 2.36) and I. cylindrica (5.37 ± 2.36) whereas the lowest ratio was recorded for C. ciliaris (1.87 ± 0.44). This suggests greater allocation of resources to root than to shoot by the species for space exploitative growth that enables them to acquire nutrients from nutritionally poor and unfavorable substratum like fly ash dump. Such a strategy enables species to establish and regenerate on barren areas that include fly ash dumps. The higher root length, spread, biomass, and root/shoot ratio in plants of all the species grown on fly ash as compared to plants grown on the native soil substantiate that plasticity in functional traits enabled the species to adapt to stressed habitats. The plastic responses observed are specific to the trait, specific to the species, and specific to the environment. This is evident by the quantitative differences in the responses between traits within a species, between species, and between habitats. The phenotypic plasticity induced by the fly ash altered the relationships between functional traits of the plants. This is evident by the marked differences in the r-values for different character associations between plants grown on fly ash dump and native soil. The results suggest that all the four grass species evaluated can be used for the rapid development of vegetation cover on the fly ash dumps to mitigate environmental contamination.

Studies on Growth and Yield Response of Jatropha curcas Plant on Fly Ash Amended Soil

ABSTRACT Fly Ash (FA) is usually considered unfavorable to plant growth and its disposal has become a serious environmental issue. However, some studies on revegetation on fly ash dumps showed some agricultural potential of the fly ash. The present study attempts to judiciously utilize the waste fly ash as a soil amendment and assess the feasibility of growth of energy plants viz. Jatropha on fly ash amended soil in varying percentages (0%, 5%, 10%, 20%). The study primarily focuses on growth and yield to judge the suitable content of fly ash favoring plant growth. Plastochron Index (PI) and plant morphological characteristics are used to assess the growth whereas, the yield is assesses based on biomass and other parameters estimated after completion of the experimental duration. The growth and yield assessment indicated better sustenance of Jatropha plant on soil amended with 10% fly ash

Plant diversity and ecological potential of naturally colonizing vegetation for ecorestoration of fly ash disposal area

Fly ash dump has been noticed as one of the hazardous dumpsites on the earth, which pollutes our environment. Therefore, an affordable and effective approach for the restoration of fly ash dumps is urgently required worldwide. In this direction, to find out potential plant species through the assessment of naturally colonized vegetation is a basic criterion of ecological restoration. With the above vision, the present study was performed to identify potential colonizer plants of fly ash dumps for ecological restoration. The intensive field studies were made during 2019–2020 to gather naturally occurring plants from fly ash disposal area of Koradi Thermal Power Plant, Nagpur, Maharashtra, India. Therefore, naturally colonizing plants were assessed on the basis of their dominance, ability of improving the rhizospheric FA, and ecological significance for their ecorestoration potential. Acacia nilotica L., Acmella oleracea L., Bacopa monnieri L., Cynodon dactylon (L.) Pers., Cyperus rotundus L., Dactyloctenium aegyptium L., Digitaria sanguinalis L., Trianthema portulacastrum L., Typha latifolia L. and Portulaca oleracea L. were recognized as potential plants for ecological restoration of FA dumps. Hence, the characteristics of above identified potential plant species can be used in ecological restoration of newly FA disposal areas.

Environmentálně rizikové chemické prvky na odkališti Brno-Hády

The studied area is located in Brno-Vinohrady. This location was used for fly ash dumping. Fly ash as a product of coal combustion was deposited there in period from 1967 to 1997 from the in the Červený mlýn and Špitálka heating plants. This material has the ability to absorb pollutants, especially heavy metals in its structure. Elevated concentrations of these elements thus represent a potential environmental risk. The main impulse to have a closer look at this waste dump and the fly ash composition is the planned building of a leisure complex in this area in the near future.The fly ash morphology was investigated by a scanning electron microscope (SEM). The results proved the presence of microspheres. On their surface, heavy metals and other contaminants can be accumulated. The contents of heavy metals were determined in the studied material by atomic absorption spectroscopy (AAS) and X-ray fluorescence (XRF) analysis. Measured values were compared with the limit values of environmental pollution published by the Ministry of the Environment of the Czech Republic and with the results of previous studies from the same place. The limits were exceeded slightly by cobalt (Me = 41.62 ppm; Max = 58.30), and a lot of arsenic (Me = 380.62; Max = 593.35). Amount of arsenic was thus compared with the exposure models, which were created for this location earlier. Its concentration transgressed the line of potential risk for a human organism. The number of radionuclides in the analyzed material by laboratory gamma-ray spectrometry (Me: K = 1.75 %, eU = 6.50 ppm, eTh = 16.75 ppm) was converted to the specific activity of 226Ra (am; Me = 212.40 Bq kg-1) and compared with the limit which is 370 Bq kg-1. Thismethod proved that the deposited material does not contain potentially dangerous amounts of natural radionuclides.Based on the results of this study, especially on the amount of arsenic, the waste dump Brno-Hády represents a potentially dangerous location for the human organism and requires adjustments for possible future utilization as a leisure complex.

Ground beetle (Coleoptera, Carabidae) communities as natural indicators of ecosystem restoration on the terminated fly ash dump of the thermoelectric power station (Novosibirsk, Russia)

The aim of the study. The aim of the study was to reveal regularities in the development of ground beetles (Coleoptera, Carabidae)’ communities, to determine their species peculiarities as dependent on soil formation rate and soil ecology in the ecosystems developed on the terminated fly ash dump of the thermoelectric power station over nine years of restoration. Location and time of the study. The main object of the study was a terminated fly ash dump No.1 of the thermoelectric power station No.5 in Novosibirsk, Russia. (54°59' NL, , 83°03' EL). Soil samples were collected in 2019, whereas the ground beetles were collected in 2017 and 2019. Methodology. Six study sites, corresponding to the fly ash dump sedimentation zones, were chosen. The undisturbed white birch forest and clover-brome meadow were chosen as controls representing mature climax ecosystems. Soil cover, developing on the fly ash dump after its termination, was described according to the soil classification of technogenic landscapes, and was shown to consist of various types of embryozems (Technosols). Soil water content on each study site was measured in 0–5cm layer by gravimetric method. Soil samples were collected in May 2019. To collect ground beetles five traps were placed on each study site, each trap filled up to 1/3 of its volume with 4% acetic acid for fixing the trapped beetles. The beetles were collected in May–June 1017 and in June–July 2019. The data obtained were used to calculate α-biodiversity indices and perform cluster analysis using PAST v.3.09 software. Main results. Altogether 74 species of the ground beetle we found: 60 species of ground beetles were identified in the revegetating fly ash dump areas, with 48 species found at the sites amended with potentially fertile substrate (PFS), and 35 species found at the sites without PFS addition. The control sites under birch forest and meadow had 14 and 10 species, respectively. Thus the ground beetles’ abundance in the reclaimed area was almost 3 times greater than in the non-reclaimed area (973 specimens vs. 347). Cluster analysis discriminated three groups in the studied fly ash dump sites, namely dry non-reclaimed sites, dry PFS sites and moist sites. Soil cover of the studied fly ash dump was represented by initial, organic matter accumulating, humus-accumulating and sod embryozems (Technosols). Conclusion. Over nine years of spontaneous restoration at the terminated fly ash dump of the thermoelectric power station species rich and abundant communities of ground beetles were formed. These communities differed significantly from those at the adjacent undisturbed climax ecosystems used for comparison. Species richness and dynamic density of ground beetles was shown to increase from the control sites to non-reclaimed sites and PFS-reclaimed sites. The autonomous position in the catena was found to be occupied by the less evolutionary developed embryozem type, whereas downwards along the catena, i.e. with increasing soil moisture content, identified soil types belonged to higher evolutionary order. Therefore technical recultivation with fly ash dump overlaying with potentially fertile substrate or fertile soil allow accelerating soil cover development, as well as the development of an entire biogeocenosis.

Adaptive Morphophysiological Features of Neottia ovata (Orchidaceae) Contributing to Its Natural Colonization on Fly Ash Deposits

In previous decades, some species of the Orchidaceae family have been found growing in man-made habitats. Neottia ovata is one of the most widespread orchids in Europe, however it is quite rare in Russia and is included in several regional Red Data Books. The purpose of this study was to compare the chemical composition and morphophysiological parameters of N. ovata from two forest communities of the Middle Urals, Russia: natural and transformed (fly ash dump of Verkhnetagil’skaya Thermal Power Station) for determining orchid adaptive features. The content of most of the studied metals in the underground parts (rhizome + roots) of N. ovata was considerably higher than in the leaves, which diminished the harmful effect of toxic metals on the aboveground organs. The adaptive changes in the leaf mesostructure of N. ovata such as an increase in epidermis thickness, the number of chloroplasts in the cell, and the internal assimilating surface were found for the first time. The orchids from the fly ash deposits were characterized by a higher content of chlorophyll b and carotenoids than plants from the natural forest community that evidenced the compensatory response on the decrease in chlorophyll a. The ability of N. ovata from the transformed habitat to maintain a relatively favorable water balance and stable assimilation indexes further contribute to its high viability. The study of orchid adaptive responses to unfavorable factors is necessary for their successful naturalization and introduction into a new environment.

Soil microbiome after nine years of fly ash dump spontaneous revegetation

Fly ash dumps of thermal power stations have been increasing in area worldwide due to the growing demand for power. One of the cost-effective approaches for restoring such sites is spontaneous revegetation in those areas where adjacent indigenous ecosystems can supply seeds and living organisms. We assessed microbiome taxonomic diversity in a Technosol developed during nine years of spontaneous revegetation of the terminated fly ash pond of a thermal power station in Novosibirsk, Russia, in comparison with microbiome diversity in undisturbed Phaeozem under adjacent birch forest by using 16S (V3–V4) and ITS2 (ITS3–ITS4) amplicon sequencing with Illumina MiSeq. We identified 577 fungal and 5542 bacterial operational taxonomic units (OTUs); 95–99% of them were minor or rare species. The dominant OTUs were completely different in the studied soils. At the phylum level, the ultimate dominants were Ascomycota (84%) in the Technosol and Basidiomycota (89%) in the Phaeozem. Three phyla (Proteobacteria, Acidobacteria and Actinobacteria), together comprising more than a half of the bacteriobiome, prevailed in both soils; however, at the OTU level, soil-related differences were found for 31% of the OTUs. The Technosol bacteriobiome was less structured and more diverse compared to the mycobiome, displaying the same phylum-level structure and OTU-based α-biodiversity as in the adjacent mature soil. Our finding that few fungal and bacterial OTUs dominated in the soil microbiome, the majority being minor or rare members, implies that key ecosystem processes performed by soil microorganisms rely on a very limited taxonomic diversity, both in young and mature soils.

Thermal process for magnesium production with Al-Si-Fe from coal fly ash: Thermodynamics and experimental investigation

Dumping or disposal of fly ash causes environmental pollution and huge waste of valuable metals. In this work, carbothermic reduction of fly ash under normal pressure to produce Al-Si-Fe alloy, and thermal reduction of magnesia to produce magnesium in vacuum with Al-Si-Fe alloy were investigated. In addition, the surface morphology and composition of Al-Si-Fe alloy and magnesium were studied by means of SEM-EDS and XRD. Based on the thermodynamic analysis, it was found that AlN and SiO2 lowered down the reduction temperature of SiC and Al4C3, respectively. Increase of temperature and decrease of vacuum degree promotes the thermal reduction of magnesia. Results showed that the recovery rate ranked Fe, Si, and Al in a descending order. The evaporation loss of gaseous SiO and Al2O reduced the recovery of Si and Al. Al-Si-Fe alloy containing 33.12% Al, 48.73% Si, and 6.41% Fe is obtained under the optimal conditions. Magnesium with the content of 94.87% is prepared using the obtained Al-Si-Fe alloy as a reductant. The nucleation rate is less than the growth rate during the condensation of magnesium vapor.

Flexural behaviour of fly ash based geopolymer concrete

The study focus on investigate the behaviour of Fly Ash Based Geopolymer Concrete. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) in the ratio of 1: 2.5 is used as an alkaline activator solution in which the concentration of NaOH is kept as 12 M. Flexural strength test were conducted on the concrete specimens. The overall result shows that the Fly ash based Geopolymer concrete composites can be utilized in construction dustry due to its eco-friendly nature and also the use of fly ash is encouraged which is generally a waste product that is generated in coal based power plants. The problem to the dumping of fly ash is also solved.

Experimental investigation on utilization of silty sand, lime, gypsum to improve mechanical properties of fly ash

Abstract Researchers globally due to little cost and effective results in engineering applications frequently use the waste material. Every year millions of ton of waste like Fly ash, lime, gypsum had generated from the kilns. In addition, mainly in this research focused on application of Silty Sand, Which have been produced on very large scale along the dam site, A huge amount of the this sand went for dumping to the nearby site. The dumping of Fly ash from industries near habitable areas poses environmental threats like air pollution, water contamination and affects biodiversity. This empirical investigation mainly focused on utilization of waste material like Silty sand, Lime and Gypsum to replace Fly ash in different mixes. In this research different mix have prepared by addition of Silty sand, Lime and gypsum to the voluminous weight of Fly ash, and silty sand have added in four different percentage of mixes to replace Fly ash by 10, 20, 30 and 40% by weight. Following tests have conducted standard proctor test and unconfined compressive strength test and final the result of test reveals that by addition of 10% of silty sand and the samples and cured by burlap method Unconfined compressive strength have highest i.e. 64.58 KPa with 56 days curing period.

Foliar Concentrations of Selected Elements, Assessment of Oxidative Stress Markers and Role of Antioxidant Defense System is Associated with Fly Ash Stress Tolerance in Withania somnifera

Increased dependence on thermal power has resulted in a significant increase in the generation of fly ash (FA), which exacerbates environmental pollution. In order to mitigate this source of pollution, we propose covering FA dumps with a layer of planted vegetation. Due to varying degrees of tolerance and their sessile nature, plants are themselves susceptible to stress from pollution. This suggests that an investigation to assess the role of wild growing plants for management of FA dumps, where selected wild plants could be grown to mitigate consequences of FA. The present study assesses oxidative damage and the foliar concentration of metals in Withania somnifera growing wild at the Badarpur Thermal Power Plant (BTPP) compared to those growing at a control site. Plants growing at the BTPP showed significantly higher foliar concentrations of Pb, Mn, and Fe, and low concentrations of Ni and Cd. The plants at the BTPP site showed signs of oxidative stress as indicated by enhanced levels of malondialdehyde and electrolyte leakage from cells. The CO2 assimilation rate, net photosynthetic rate, rate of transpiration, stomatal conductance decrease, while water use efficiency, and air pollution tolerance index increase. Among air pollution tolerance index parameters, relative water content showed a significant increase with FA pollution stress at the BTPP. A significant decrease was observed in leaf morphology single leaf area, leaf length, and leaf width and biochemical parameters (Chlorophyll a, Chlorophyll b, total chlorophyll, and carotenoids. Moreover, FA pollution stress induces oxidative stress in W. somnifera through a significant and enhanced production of reactive oxygen species (ROS). According to our observations, the ability of W. somnifera to effectively coordinate superoxide dismutase, ascorbate peroxidase, and glutathione reductase activities involved in the scavenging of ROS along with the enhanced increment of nonenzyme activities (total ascorbic acid, proline, and oxidized glutathione) could be related to FA stress tolerance in W. somnifera.

Metal remediation potential of naturally occurring plants growing on barren fly ash dumps.

The present study aimed to elucidate the remediation potential of visibly dominant, naturally growing plants obtained from an early colonized fly ash dump near a coal-based thermal power station. The vegetation comprised of grasses like Saccharum spontaneum L., Cynodon dactylon (L.) Pers., herbs such as Tephrosia purpurea (L.) Pers., Sida rhombifolia L., Dysphania ambrosioides (L.) Mosyakin & Clemants, Chromolaena odorata (L.) King & H.E. Robins along with tree saplings Butea monosperma (Lam.) Taub. The growth of the vegetation improved the N and P content of the ash. Average metal concentrations (mgkg-1) in the ash samples and plants were in order Mn (345.1) > Zn (63.7) > Ni (29.3) > Cu (16.8) > Cr (9.9) > Pb (1.7) > Cd (0.41) and Cr (58.58) > Zn (52.74) > Mn (39.09) > Cu (10.71) > Ni (7.45) > Pb (5.52) > Cd (0.14), respectively. The plants showed fly ash dump phytostabilization potential and accumulated Cr (80.19-178.11mgkg-1) above maximum allowable concentrations for plant tissues. Positive correlations were also obtained for metal concentration in plant roots versus fly ash. Saccharum spontaneum showed highest biomass and is the most efficient plant which can be used for the restoration of ash dumps.

Physiological profiling of invasive plant species for ecological restoration of fly ash deposits

Extensive gaps in invasive plant species research in terms of ecosystem distribution and impact are major barriers faced by global decision making bodies for scientific management of plant species invasions of native flora. Effective strategies need to be worked out which would enable simultaneous management and the use of invasive plant species for ecosystem restoration. For evaluating the photosynthetic potential of invasive plant species in restoration of degraded areas, exhaustive in situ leaf gas exchange and leaf chlorophyll fluorescence were undertaken on four plants found naturally colonizing on the fly ash deposits. The four invasive species screened for their physiological tolerances towards microclimatic and edaphic stresses in harsh fly ash deposits were: Typha latifolia, Saccharum spontaneum, Prosopis juliflora, and Ipomea carnea. Saccharum spontaneum was found to be most efficient in sequestering CO2 emissions which were reflected in its maximum net photosynthetic rate (A, 29.29 ± 0.46 μmolCO2 m−2s−1) and higher below ground biomass. Maximum water use efficiency (WUE) was observed in S. spontaneum (9.3 ± 0.5 mmolCO2 molH2O−1) among all the species owing to high carboxylation, the lowest transpiration rate (E, 3.15 ± 0.13 mmolH2Om−2s−1) and stomatal conductance (gs, 0.2 ± 0.004 molH2Om−2s−1) values supporting it’s dense growth throughout the fly ash dumps in contrast to other three species. The study provides insights into the successful use of invasive plant species for their effective management and phytorestoration of fly ash dumps by transforming them into net carbon sinks which otherwise lack any native flora.

A feasibility study of Indian fly ash-bentonite as an alternative adsorbent composite to sand-bentonite mixes in landfill liner

Multi-layered engineered landfill consists of the bottom liner layer (mainly bentonite clay (B)) upon which the hazardous wastes are dumped. In current practice, sand (S) is mixed with bentonite to mitigate the adverse effects of using bentonite alone in the liner layer. Incorporation of waste and unutilized fly ash (FA) as an amendment material to B has been explored in terms of its hydro-mechanical properties, but not gauged its adsorption potential. Indian subcontinent primarily relies on the thermal power source, and FA dumps have already reached its full capacity. The objective of this study is to explore the adsorption characteristics of four B-FA composite mixes sourced within India, considering Pb2+ as a model contaminant. The effect of fly ash type, fly ash amendment rate and adsorbate concentration was explored in the current study and juxtaposed with B-S mixes, based on 960 batch adsorption tests. Both B-FA and B-S mixes reached equilibrium adsorption capacity within 65 min. At higher adsorbate concentrations (commonly observed in the liner), B-FA mixes exhibited superior adsorption capacity, mainly one mixed with Neyvelli fly ash (NFA). The effect of higher amendment rate had little impact on the adsorption capacity at different concentration, but gradually decreased the percentage removal of Pb2+. The B-S mix showed a drastic decrease in percentage removal at higher adsorbate concentration among all tested mixes. Systematic characterization including geotechnical properties, microstructure and chemical analysis was also done to interpret the obtained results. Both Freundlich and Langmuir models fitted the isotherm data well for all B-FA mixes. The maximum adsorption capacity from the isotherm was correlated to easily measurable Atterberg limits by two empirical relationships.

Utilization of Fly Ash and Waste Ceramic in Improving Characteristics of Clayey Soil: A Laboratory Study

Fly ash is a waste product obtained from coal-based thermal power stations. In the absence of proper utilization, large quantities of fly ash are dumped in the landfills. Since traces of heavy metals are present in coal, the dumping of fly ash in landfills is not ecofriendly and leads to air pollution and groundwater contamination. The ceramic tile waste is obtained from construction and tile industries which poses disposal problems and requires dumping areas causing environmental concerns. The inherent properties of these waste materials can be exploited by using in road pavement subgrade and thus solving the disposal problems. This experimental study was performed to assess the efficiency of using fly ash and waste ceramic along with poor sand for clayey soil stabilization by evaluating compaction, strength and drainage properties to be used as road sub-grade material. The addition of sand to clayey soil decreased the optimum moisture content (OMC), increased the maximum dry density (MDD) whereas the California bearing ratio (CBR) improved. Further, adding fly ash to clayey soil increased OMC value, decreased MDD value but improved the CBR value. The results indicate that adding ceramic tile waste reduced MDD value and increased OMC value and the CBR value. The drainage characteristics of composite material were better than those of clayey soil or fly ash. The stabilization of sub-grade resulted in significant savings in terms of the material required for subgrade of road pavement compared to those using un-stabilized soil. The composite containing optimum contents of clay, sand, fly ash and ceramic waste possessed better sub-grade and drainage properties and thus can be used successfully for construction of pavement subgrade of low cost roads.