Pond Ash Research Articles

Behaviour of model footing on pond ash

This paper focuses on the effective utilization of pond ash, as foundation medium. A series of laboratory model tests have been carried out using square, rectangular and strip footings on pond ash. The effects of dry density, degree of saturation of pond ash, size and shape of footing on ultimate bearing capacity of shallow foundations are presented in this paper. Local shear failure of a square footing on pond ash at 37% moisture content (optimum moisture content) is observed up to the values of dry density 11.20 kN/m3 and general shear failure takes place at the values of dry density 11.48 kN/m3 and 11.70 kN/m3. Effects of degree of saturation on ultimate bearing capacity were studied. Experimental results show that degree of saturation significantly affects the ultimate bearing capacity of strip footing. The effect of footing length to width ratio (L/B), on increase in ultimate bearing capacity of pond ash, is insignificant for L/B ≥ 10 in case of rectangular footings. The effects of size of footing on ultimate bearing capacity for all shapes of footings viz., square, rectangular and strip footings are highlighted.

Postconstruction Environmental Monitoring of a Fly Ash-Based Road Subbase

This paper discusses the results of post-construction environmental monitoring studies performed on a 3.4-km-long industry access truck route with unstabilized F-fly ash subbase. The road utilized approximately 60,000 m3 of ponded F-fly ash as road subbase, generated by a nearby power plant. Long-term environmental monitoring has been an integral part of the project since the construction of the road in October 2002. Six, 9-m-deep boreholes were developed as monitoring wells around the project site to evaluate the direction of groundwater flow and changes in water quality over time. Preconstruction water quality studies were performed on water samples collected from the monitoring wells in June 2000, to establish baseline water quality data for groundwater. Samples of fly ash taken from the stockpile were subjected to leaching studies prior to construction of the road. In total, five water quality samples were collected from the monitoring wells at regular intervals, as part of the postconstruction monito...

A Study for Evaluation of Contaminant Transport Characteristics Through Fine‐Grained Soil

Transport of soluble toxic substances through porous media lead to some significant geoenvironmental problems, for example, leachate migration from municipal and industrial solid waste resulting from unregulated disposal. Advection, dispersion, diffusion, and decay are reported to be the principal mechanisms in such phenomena. Geotechnical properties of the soil also play a significant role in this deterioration. In the present study, laboratory tests were conducted to formulate an appropriate method for assessment of migration of metal ions, such as nickel, through the soil. Relevant kinetic and process parameters, such as aquifer data, surface area, dielectric constant, pH of zero point charge (pHzpc), and permeability were also studied. One-dimensional mathematical modeling was used to describe the dynamics of the process. The present investigation was carried out at an ash pond site of a thermal power plant situated in West Bengal, India.

Mathematical Modeling of Leachates from Ash Ponds of Thermal Power Plants

The present study describes the development of empirical models for the prediction of various trace metals i.e., Mn, Cu, Fe, Zn and Pb found in the leachates generated from the ash ponds of various thermal power plants. The dispersion phenomenon of these trace metals followed first order reaction rate kinetics. The empirical models for individual trace metals derived from the lab scale models data correlate well with the real field data with regression coefficients varying from 0.93 to 0.98. The predicted concentrations of the trace metals varied within +/-3% of the observed values in the leachates generated from the ash ponds of four thermal power plants with standard deviation varying from 0.001 to 0.032. The empirical models derived from the study can be applied for prediction of trace metals in leachates generated from similar thermal power plants.

An assessment of soil contamination due to heavy metals around a coal-fired thermal power plant in India

Combustion of coals in thermal power plants is one of the major sources of environmental pollution due to generation of huge amounts of ashes, which are disposed off in large ponds in the vicinity of the thermal power plants. This problem is of particular significance in India, which utilizes coals of very high ash content (∼55 wt%). Since the thermal power plants and the ash ponds are located in densely populated areas, there is potential chance for contamination of soil and groundwater of the surrounding areas from the toxic trace elements in the ash. An attempt has been made to study the extent of soil contamination around one of the largest thermal power plants of India located at Kolaghat, West Bengal India. Chemical analysis of the top soils and the soils collected from the different depth profiles surrounding the ash ponds, show that the top soils are enriched in the trace elements Mo, As, Cr, Mn, Cu, Ni, Co, Pb, Be, V, Zn, which show maximum enrichment (2–5) in the top soils collected from all the soil profiles. These elements are also enriched in the pond ash. Since there are no other sources of industrial effluents, it can be said that the enrichment of the trace elements (Mn, Co, Mo, Cr, Cu, Pb, Zn, As, Ni, Be, V) is attributed to their input from ash from the disposal pond. The study has been further strengthened by log-normal distribution pattern of the elements.

Analysis of fly ash heavy metal content and disposal in three thermal power plants in India

The study investigates the heavy metal content of fly ash and bottom ash from three major power plants in North India, using flame atomic absorption spectrometry. It also studies the prevalent disposal methods used at these sites. The ashes were analysed for the presence of Cr, Mn, Pb, Zn, Cu, Ni and Co and detectable levels of all were found in both fly ash and bottom ash. The concentrations of Cr and Zn were highest while Co concentration was less. The wet disposal method is used in two of the power plants (site 1 and site 3). Neither of the sites uses ash pond lining in the construction of the ash ponds, hence leaching of the heavy metals is possible. Site 2 has adopted 100% dry disposal system which allows better utilization but incurs additional costs. Better management practices, increased utilization and proper disposal practices need to be undertaken to minimize the adverse environmental impact.

A geotechnical classification system for coal ashes

Most of the existing soil classification systems make use of the plasticity chart for classifying fine-grained soils and some coarse-grained soils as well. They cannot classify those granular materials that are non-plastic through appropriate group symbols indicative of their non-plastic nature without any ambiguity. Coal ashes, consisting of fly ash (known as pulverised fuel ash in the UK), bottom ash and pond ash, are produced in large quantities and are occasionally used in geotechnical applications. As they are non-plastic materials, the existing classification systems fail to classify them appropriately. This paper discusses this issue in detail. A classification system for coal ashes that are essentially non-plastic is formulated and proposed in this paper. It is shown through illustrative examples that the coal ashes can be classified easily and without any ambiguity using the proposed system.

Glass ceramic foams from coal ash and waste glass: production and characterisation

Lightweight glass ceramic foams have been produced from a mixture of silicate wastes, namely 20 wt-% coal pond ash and 80 wt-% bottle glass cullet. A powder sintering route with the incorporation of 2 wt-%SiC as foaming agent was used. The pore morphology achieved under different sintering conditions was investigated in detail using X-ray microtomography. The apparent density of the foams ranged from 0·2 to 0·4 g cm−3, and the porosity ranged from 70 to 90%. Other variables, such as pore wall thickness, pore size and roundness, all behaved consistently with sintering temperature. The optimum sintering temperature was found to be in the range 1000–1050°C, at which porosity was about 75% and was the most uniform. Foams produced under this condition exhibit satisfactory compressive strength of about 1·5 MPa and show relatively high thermal shock resistance, with compressive strength gradually decreasing as quenching temperature increases.

Toxicity and Hazard of Vanadium to Mallard Ducks (Anas platyrhynchos) and Canada Geese (Branta canadensis)

A recent Canada goose (Branta canadensis) die-off at a petroleum refinery fly ash pond in Delaware was attributed to vanadium (V) toxicity. Because of the paucity of V toxicity data for wild birds, a series of studies was undertaken using the forms of V believed to have resulted in this incident. In 7-d single oral dose trials with mallard drakes (Anas platyrhynchos), the estimated median lethal dose (LD50) for vanadium pentoxide was 113 mg/kg body weight, while the LD50 for sodium metavanadate was 75.5 mg/kg. Sodium metavanadate was found to be even more potent (LD50 = 37.2 mg/kg) in male Canada geese. The most distinctive histopathological lesion of both forms of V was lympho-granulocytic enteritis with hemorrhage into the intestinal lumen. Vanadium accumulation in liver and kidney was proportional to the administered dose, and predictive analyses based on these data suggest that V concentrations of 10 μg/g dry weight (dw) in liver and 25 μg/g dw in kidney are associated with mortality (>90% confidence that exposure is >LD50) in mallards acutely exposed to sodium metavanadate. Chronic exposure to increasing dietary concentrations of sodium metavanadate (38.5 to 2651 ppm) over 67 d resulted in V accumulation in liver and kidney (25.2 and 13.6 μg/g dw, respectively), mild intestinal hemorrhage, blood chemistry changes, and evidence of hepatic oxidative stress in mallards, although some of these responses may have been confounded by food avoidance and weight loss. Dietary exposure of mallards to 250 ppm sodium metavanadate for 4 wk resulted in modest accumulation of V in liver and kidney (<5 μg/g dw) and mild intestinal hemorrhage. Based on these data and other observations, it is unlikely that chronic low-level dietary exposure to V poses a direct lethal hazard to wildlife. However, point sources, such as the V-laden fly ash pond encountered by geese at the petroleum refinery in Delaware, may pose a significant hazard to water birds.

Estimation of freeboard requirements against overtopping of surface impoundments under seismic action

The excitation of structural components and liquid contents of surface impoundments by seismic waves can generate turbulence that is large enough to overtop the bounding berms. In cases in which the liquids are wastes from industrial/municipal operations, their release from impoundments can pose significant risks to the environment. In this analysis, the freeboard magnitudes that can accommodate liquid head levels in impoundments are determined through linkage of configuration of waves in the liquid surface to incident seismic wave characteristics, liquid characteristics and impoundment design. For an impoundment site in a region of ground acceleration levels ranging from 0.2 to 1.0 g and impacted by seismic shear wave velocity of 180 m/s, freeboard requirements are in the range of 0.004–2.0 m on soft soil; 0.008–0.7 m on medium-dense soil; and 0.002–0.1 m for dense soil. For the same impoundment design, ground acceleration and incident wave characteristics, freeboard requirements are directly proportional to the depth of the soil mantle over bedrock. The impoundment slope, which is a key parameter with regards to liquid holding volumetric capacity of the impoundment, is a less significant parameter than depth to bedrock with regard to the size of the required freeboard. This implies that siting of an impoundment should be considered to be critical to impoundment performance in seismic zones.

Effect of Aggregate Gradation, Mineral Fillers, Bitumen Grade, and Source on Mechanical Properties of Foamed Bitumen–Stabilized Mixes

With the rapid growth of traffic volumes and axle loads, the use of efficient and cost-effective stabilization methods is imperative. The use of foam bitumen stabilization is rapidly growing because of its environmentally friendly benefits and its high field performance properties. In this study, a detailed investigation of the mechanical properties of foam-stabilized mixes was carried out. The experimental work presented compares the mechanical properties of foam-stabilized mixes created with two different gradations and eight bitumen types from six different sources. Different types of mineral fillers, including hydrated lime, fly ash type C, portland cement, and pond ash, were used in the mix design. The volumetric properties, resilient moduli, indirect tensile strengths, fracture energies, and California bearing ratio (CBR) values were investigated. Temperature and moisture susceptibilities were studied and compared for different types and grades of bitumen. Foam-stabilized mixes provided lower temperature susceptibility than did hot-mix asphalt. The effect of bitumen source and grade on moisture susceptibility was inspected. The foam-stabilized mixes provided reasonable moisture resistance as the index of retained strength exceeded 80% to 90% after 5 days of soaking. The effect of aggregate gradation and mineral fillers on the indirect tensile strength and the fracture energy was evident. Hot-mix asphalts provided higher tensile strength and fracture energy than did foam-stabilized mixes. Foamed bitumen stabilization significantly enhanced the CBR values as the soaked CBR of foam-treated specimens provided higher CBR values than the conventional untreated aggregates.

Effect of Aggregate Gradation, Mineral Fillers, Bitumen Grade, and Source on Mechanical Properties of Foamed Bitumen-Stabilized Mixes

With the rapid growth of traffic volumes and axle loads, the use of efficient and cost-effective stabilization methods is imperative. The use of foam bitumen stabilization is rapidly growing because of its environmentally friendly benefits and its high field performance properties. In this study, a detailed investigation of the mechanical properties of foam-stabilized mixes was carried out. The experimental work presented compares the mechanical properties of foam-stabilized mixes created with two different gradations and eight bitumen types from six different sources. Different types of mineral fillers, including hydrated lime, fly ash type C, portland cement, and pond ash, were used in the mix design. The volumetric properties, resilient moduli, indirect tensile strengths, fracture energies, and California bearing ratio (CBR) values were investigated. Temperature and moisture susceptibilities were studied and compared for different types and grades of bitumen. Foam-stabilized mixes provided lower temperature susceptibility than did hot-mix asphalt. The effect of bitumen source and grade on moisture susceptibility was inspected. The foam-stabilized mixes provided reasonable moisture resistance as the index of retained strength exceeded 80% to 90% after 5 days of soaking. The effect of aggregate gradation and mineral fillers on the indirect tensile strength and the fracture energy was evident. Hot-mix asphalts provided higher tensile strength and fracture energy than did foam-stabilized mixes. Foamed bitumen stabilization significantly enhanced the CBR values as the soaked CBR of foam-treated specimens provided higher CBR values than the conventional untreated aggregates.

Investigation of occupational radiation exposures to NORM at an Irish peat-fired powerstation and potential use of peat fly ash by the construction industry

Annually, approximately 15% of Ireland’s electricity requirement is provided through the combustionof 3 × 106 tonnes of peat. While the literature on coal-fired power generation is quite abundant,studies on the peat-fired power generation industry from a radiological point of view arescarce. A study of the largest Irish peat-fired power plant was initiated to review thepotential occupational radiation exposures arising from the occurrence of naturallyoccurring radioactive material (NORM) at different stages of the industrial process and toinvestigate any radiological health consequences that may arise should peat fly ash be usedas a component of building materials. Ambient gamma dose rate measurements, radonmeasurements, quantification of the occupational exposure from inhalation of airborneparticles (personal air sampling) and gamma spectrometry analysis of peat, peat ashand effluent samples from the ash ponds were undertaken. The results indicatethat the radiation dose received by any worker involved in the processing of thepeat and the handling of the ash resulting from peat combustion does not exceed150 µSv per annum. Regulatory control of the peat-fired power generation is therefore unnecessaryaccording to the Irish legislation with regards to NORM. The potential use ofpeat fly ash as a by-product in the building industry was also found to have anegligible radiological impact for construction workers and for members of thepublic.

Free Swell Characteristics of PCC Bottom Ash-Bentonite Mixtures with Curing for Use as Fill or Liner Material

Bottom ash is a coal combustion product (CCP) obtained from burning of pulverized coal to produce electricity. Most of the bottom ash from pulverized coal combustion (PCC) plants is disposed of in landfills and/or ash ponds. Over the last decade, there has been increased attention aimed toward the use of PCC bottom ash in geotechnical applications. The particle size distribution of pulverized coal combustion (PCC) bottom ash is similar to that of natural sand. Natural sand is commonly used in the construction industry in place of cohesive soils by adding admixtures to amend its properties. Several studies have been completed to determine the properties of bottom ash amended with bentonite. However, due to significant volume change characteristics of bentonite, soils or similar granular materials amended with it need to be evaluated for their swelling behavior. In addition, studies on bottom ash-bentonite mixtures have shown that strength and stiffness characteristics of these mixtures change significantly with curing. Therefore, in order to evaluate the use of bottom ash as a fill or landfill liner material, this study was initiated to investigate the effect of curing and moisture content on the swelling characteristics of pulverized coal combustion bottom ash amended with bentonite. Bottom ash specimens containing 15 and 20 percent bentonite and prepared at 14, 16 and 18 percent initial moisture content were tested in this investigation. Results presented show the swelling characteristics of bottom ash-bentonite mixtures with curing age up to 60 days.

Impact of land disposal of reject brine from desalination plants on soil and groundwater

The impact of reject brine chemical composition and disposal from inland desalination plants on soil and groundwater in the eastern region of Abu Dhabi Emirate, namely Al Wagan, Al Quaa and Um Al Zumool, was evaluated. Twenty five inland BWRO desalination plants (11 at Al Wagan, 12 at Al Quaa, and 2 at Um Al Zumool) have been investigated. The study indicated that average capacity of these plants varied between 26,400 G/d (99.93 m 3/d) to 61,000 G/d (230.91 m 3/d). The recovery rate varied from 60 to 70% and the reject brine accounted for about 30–40% of the total water production. The electrical conductivity of feed water and rejects brine varied from 4.61 to 14.70 and 12.90–30.30 (mS/cm), respectively. The reject brine is disposed directly into surface impoundment (unlined pits) in a permeable soil with low clay content, cation exchange capacity and organic matter content. The groundwater table lies at a depth of 100–150 m. The average distance between feed water intake and the disposal site is approximately 5 km. A survey has been conducted to gather basic information, determine the type of chemicals used, and determine if there is any current and previous monitoring program. The chemical compositions of the feed, product, reject, and pond water have been analyzed for major, minor and trace constituents. Most of the water samples (feed, product, reject and pond water) showed the presence of major, minor and trace constituents. Some of these constituents are above the Gulf Cooperation Council (GCC) and Abu-Dhabi National Oil Company (ADNOC) Standards for drinking water and effluents discharged into the desert. Total Petroleum Hydrocarbon (TPH) was also analyzed and found to be present, even in product water samples, in amount that exceed the GCC standards for organic chemical constituents in drinking water (0.01 mg/l).

Effect of Coal Ash on Growth and Metal Uptake by Some Selected Ectomycorrhizal Fungi in vitro

Six isolates of ectomycorrhizal fungi namely, Laccaria fraterna(EM-1083), Pisolithus tinctorius (EM-1081), Pisolithus tinctorius (EM-1290), Pisolithus tinctorius (EM-1293), Scleroderma verucosum (EM-1283), and Scleroderma cepa (EM-1233), were grown on three variants of coal ash, namely electrostatically precipitated (ESP) ash, pond ash, and bottom ash moistened with Modified Melin-Norkans (MMN) medium in vitro. The colony diameter reflected the growth of the isolates on the coal ash. Metal accumulation in the mycelia was assayed by atomic absorption spectrophotometry. Six metals, namely aluminum, cadmium, chromium, iron, lead, and nickel, were selected on the basis of their abundance in coal ash and toxicity potential for the present work. Growth of vegetative mycelium on fly ash variants and metal accumulation data indicated that Pisolithus tinctorius (EM-1290) was the most tolerant among the isolates tested for most of the metals. Since this isolate is known to be mycorrhizal with Eucalyptus, it could be used for the reclamation of coal ash over burdened sites.

Disaster Management for Nandira Watershed District Angul (Orissa) India, Using Temporal Remote Sensing Data and Gis

NALCO--the largest exporter of aluminium in India has a power plant of 720 MW capacity in Nandira watershed in Angul district of Orissa. The power plant utilises local coal to generate thermal power and disposes of large amount of ash which accumulates in slurry form at nearby two ash ponds. These ash ponds were breached on 31 December 2000, causing ash accumulation for entire regime of the Nandira river. An attempt has been made towards preparation of recovery and rehabilitation plan for NALCO using temporal Remote Sensing data and GIS. Indian remote sensing satellite data for pre-breach condition 12 December 2000, during breach event 31 December 2000 and post-breach condition 4 and 6 January 2001 has been digitally analysed for Nandira watershed. The satellite data of coarse spatial resolution provides the absence and presence of fresh sediment deposition along Nandira watershed and Brahmani river pertaining to pre-breach and post-breach conditions respectively on regional scales. The temporal comparison of fine resolution has clearly highlighted the aerial extent of damage caused by the disaster for entire watershed on local scales. The GIS has helped in demarcation of freshly accumulated ash at interval of 500 m along the river length as well as in delineation of maximum ash accumulation across the river width. The study has clearly demonstrated the use of temporal Remote Sensing data in conjunction with GIS for disaster management in terms of recovery and rehabilitation plan preparation of the Nandira watershed.

Genetic algorithm for cost optimization of modified multi-component binders

This paper describes the application of a genetic algorithm for the cost optimization of a modified multi-component binder (MMCB). An MMCB comprised of Portland cement (NPC), finely ground mineral additives (fly ash, ponded ash or granulated blast furnace slag), and a highly reactive powder component (usually silica fume, SF) was modified by a superplasticizer (SP). Strength models based on the experimental results were developed. The present work is oriented to the minimization of the MMCB cost for specific strength levels with the help of a changing range genetic algorithm (CRGA) to handle the nonlinear constraints imposed by the MMCB models. The developed CRGA is based on an approach that adaptively shifts and shrinks the size of the search space to the feasible region. The application of CRGA helps to minimize the cost of MMCB with a low resolution of the binary representation scheme and without additional computational efforts.

Characterization of an F-Class Fly Ash for Use as a Road Sub-base

An F-class fly ash was tested in the laboratory for its physical and mechanical properties for use as a road sub-base in portions of a 2.1-mi (3.4-km) truck by-pass route in east-central Illinois. The testing showed that the fly ash would perform adequately and behave predictably as a road sub-base. Construction of the by-pass route started in early June 2002 and was finished in early September 2002. No unanticipated delays were encountered, and the performance of the fly ash fill exceeded expectations. Hopefully, these positive results will promote other projects around the country to use by-products of coal combustion products, especially fly ash, as suitable fill materials. This project was a co-operative development and demonstration effort among the Office of Coal Development and Marketing (OCDM) of the Illinois Department of Commerce and Economic Opportunity (IDCEO), Southern Illinois University at Carbondale (SIUC), Morgan County Highway Department (MCHD), Illinois Department of Transportation (IDOT), AmerenCIPS, and the Morgan County Regional Planning Commission. These agencies provided both funding and matching funds to carry this project to completion. The by-pass route was designed to move truck traffic around the southern and eastern sides of the small town of Meredosia, Illinois. One problem the proposed by-pass project encountered was the source of construction materials for the sub-base fill. The project needed an additional 77,000 yd.3 (59,000 m3) of fill for the sub-base. Because of the geology in the Meredosia area, one source of material for the sub-base was sand from a borrow pit. Several other possible sources were investigated, but most were too expensive for the limited budget. The alternative chosen was to use ponded F-class fly ash from the AmerenCIPS Meredosia power plant adjacent to the truck by-pass route. The first task of the project was to determine the physical and material properties …

Effect of Organic Amendments on the Oxygen Uptake of Pseudomonas putida—PAPs-1 in Chromium-Contaminated Pond Ash

In this study a Cr (VI) resistant bacterium Pseudomonas putida was isolated from pond ash and its oxygen consumption potential at different concentrations of Cr (VI) viz., 0, 100 and 200 mg kg−1 was studied using Electrolytic Respirometry. Oxygen consumption by the bacterium was noticed up to 200 mg kg−1 Cr (VI) concentration. To the pond ash (inoculated with and without Pseudomonas) 200 mg kg−1 Cr (VI) was added and incorporated with different organic amendments such as farmyard manure (FYM), coir pith, paddy straw and press mud and the cumulative oxygen consumption was studied. The cumulative oxygen consumption by the bacterium was higher when the pond ash was incorporated with organic amendments. The highest oxygen consumption of 205 mg l−1 was observed when press mud was used, which was followed by FYM (198 mg l− 1 ). Furthermore, the enrichment with press mud increased the nutrient content of N (57.28 mg kg−1 ), P (5.5 mg kg−1 ) and K (42.7 mg kg−1 ) of the pond ash. The maximum dehydrogenase enzyme activity of 0.63 μ g TPF formed g−1 sample h−1 was measured when the pond ash was inoculated with Pseudomonas and enriched with press mud. The results also indicated that maximum reduction of Cr (VI) (42.5%) was observed when Pseudomonas and press mud were used. This study evaluated the possibilities of toxicity reduction and nutrient enrichment of the ash pond using a Cr (VI) resistant bacterium and organic amendments.