Phosphorus removal by fly ash

The aim of this work was to investigate the possible use of fly ash generated from thermic power stations in the removal of phosphorus contained in aqueous solutions. A series of batch tests were conducted and the influence of temperature, phosphate concentration, and fly ash dosage on phosphate removal were investigated. The effect of adsorption dosage was not significant at any temperature applied. Phosphate removal in excess of 99% was obtained in these studies. Maximum removals were achieved at 40°C. The tests were also carried out on a continuous basis in an adsorption column. It was found that fly ash is an efficient adsorbent for phosphate removal. This was expected due to the high concentration of calcite present in the fly ash (338 g/kg). The phosphate removal decreased to 80.4% at the end of 72 h.     

Size dependent cytotoxicity of fly ash particles

Fly ash samples were collected from the electrostatic precipitator of a coal-fired power plant in Hong Kong. The particles of the respirable range (smaller than 10 μm) were divided into 4 groups according to their particle size (mass median aerodynamic diameters). The surface morphology and the metal contents (Fe, Mn, Al and Zn) of fly ash particles were examined by a scanning electron microscope and an inductively coupled plasma spectrophotometer, respectively. The particles were very heterogenous in size and shape as well as the concentration of metals. The cytotoxicity of these four groups of fly ash particles was evaluated using an in vitro rat alveolar macrophages culture assay. The viability of alveolar macrophages was lower when incubated with smaller size particles. This relationship was also reflected by the damage of the surface morphology of the cells and the release of cytoplasmic (lactate dehydrogenase) and lysosomal (acid phosphatase and β-glucuronidase) marker enzymes into the culture media.     

Radon exhalation of cementitious materials made with coal fly ash: Part 1--scientific background and testing of the cement and fly ash emanation

Increased interest in measuring radionuclides and radon concentrations in fly ash, cement and other components of building products is due to the concern of health hazards of naturally occurring radioactive materials (NORM). The current work focuses on studying the influence of fly ash (FA) on radon-exhalation rate (radon flux) from cementitious materials. The tests were carried out on cement paste specimens with different FA contents. The first part of the paper presents the scientific background and describes the experiments, which we designed for testing the radon emanation of the raw materials used in the preparation of the cement-FA pastes. It is found that despite the higher (226)Ra content in FA (more than 3 times, compared with Portland cement) the radon emanation is significantly lower in FA (7.65% for cement vs. 0.52% only for FA).     

Leachability of elements from sub-bituminous coal fly ash from India

Environmental concerns regarding the potential contamination of soil, surface and ground water due to the presence of soluble metal species in the ash pond leachate is of great importance. Serial batch leaching was carried out simulating the rainwater condition of the study area to understand the behaviour of elements during leaching. The leachates were analysed for the elements Al, Ca, K, Mg, Na, P, S, Si, As, Ba, Fe, Mn, Mo, Ti, V, Pb, Zn, Co, Cr, Cu, Ni and Cd by inductively coupled plasma optical emission spectrometer (ICP-OES). It was found that Cd, Co, Cr and Ni did not leach from the ash while Cu and Pb concentrations were insignificant in the leachate regardless of liquid to solid (L/S) ratio. Most of the elements showed maximum concentrations at lower L/S ratio and then decreased with increasing L/S. The total cumulative concentrations of As, Mn and Mo were found to be higher than the World Health Organization (WHO) recommended values for drinking water while the concentrations of Fe, Mn and As exceeded the maximum allowable concentrations prescribed by the United States Environmental Protection Agency (USEPA). The pre and the post leached ash samples were analysed for morphology, specific surface area and mineralogical changes. Analysis of post-leached fly ash indicated changes in the specific surface area and morphology but no change in mineralogy.     

Properties of alkali-activated fly ash: high performance to lightweight

Alkali ash material (AAM) concrete is a unique material that is sustainable and cost-effective because it utilises waste fly ash, and has properties superior to other concrete products. The AAM concrete described here is produced from the addition of inexpensive chemicals to fly ash. AAM can be used to create a wide range of materials including high performance concrete (HPC-AAM) and lightweight (LW-AAM). The high performance AAM provides rapid strength gain along with high ultimate strengths of more than 110 MPa (16000 psi). LW-AAM can produce materials with densities ranging from 1200 to 2200 kg/m³ and compressive strengths from 2 (290 psi) to 65 MPa (9500 psi). Both HPC-AAM and LW-AAM have far better environmental resistance than Portland cement concrete, resisting attack from sulphuric acid (H₂SO₄), hydrochloric acid (HCl) and organic acids. AAMs resists freeze–thaw attack and high abrasion, possesses low chloride permeability and does not exhibit alkali silica reactivity.     

Radon exhalation of cementitious materials made with coal fly ash: Part 2--testing hardened cement-fly ash pastes

Increased interest in measuring radionuclides and radon concentrations in fly ash (FA), cement and other components of building products is due to the concern about health hazards of naturally occurring radioactive materials (NORM). The paper focuses on studying the influence of FA on radon exhalation rate (radon flux) from cementitious materials. In the previous part of the paper the state of the art was presented, and the experiments for testing raw materials, Portland cement and coal fly ash, were described. Since the cement and FA have the most critical role in the radon release process relative to other concrete constituents (sand and gravel), and their contribution is dominant in the overall radium content of concrete, tests were carried out on cement paste specimens with different FA contents, 0-60% by weight of the binder (cement+FA). It is found that the dosage of FA in cement paste has a limited influence on radon exhalation rate, if the hardened material is relatively dense. The radon flux of cement-FA pastes is lower than that of pure cement paste: it is about approximately 3 mBq m(-2) s(-1) for cement-FA pastes with FA content as high as 960 kg m(-3).     

Revegetating fly ash landfills with Prosopis juliflora L.: impact of different amendments and Rhizobium inoculation

A revegetation trial was conducted to evaluate the feasibility of growing a legume species, Prosopis juliflora L., on fly ash ameliorated with combination of various organic amendments, blue-green algal biofertilizer and Rhizobium inoculation. Significant enhancements in plant biomass, photosynthetic pigments, protein content and in vivo nitrate reductase activity were found in the plants grown on ameliorated fly ash in comparison to the plants growing in unamended fly ash or garden soil. Higher growth was obtained in fly ash amended with blue-green algae (BGA) than farmyard manure or press mud (PM), a waste from sugar-processing industry, due to the greater contribution of plant nutrients, supply of fixed nitrogen and increased availability of phosphorus. Nodulation was suppressed in different amendments of fly ash with soil in a concentration-duration-dependent manner, but not with other amendments. Plants accumulated higher amounts of Fe, Mn, Cu, Zn and Cr in various fly ash amendments than in garden soil. Further, inoculation of the plant with a fly ash tolerant Rhizobium strain conferred tolerance for the plant to grow under fly ash stress conditions with more translocation of metals to the above ground parts. The results showed the potential of P. juliflora to grow in plantations on fly ash landfills and to reduce the metal contents of fly ash by bioaccumulation in its tissues.     

Assessment of hydrothermally modified fly ash for the treatment of methylene blue dye in the textile industry wastewater

Dyes and pigments are one of the major water pollutants and if not discharged properly cause ecological disturbance. Considering this, the current study investigates the application of thermal power plant by-product, i.e., fly ash for the elimination of a hazardous methylene blue dye from its synthetic aqueous solution. Experiments were conducted in batch mode to study the effect of pH, temperature, adsorbent dose and contact time. Highest dye removal (94.3%) was achieved at pH 10 using adsorbent dose of 10 g/L in 90 min of contact time at 40 °C. However, for cost-effective operation at neutral pH and room temperature (30 °C), it yields 89.3% dye removal having similar dose and contact time. Equilibrium isotherms for adsorption were analyzed by Langmuir and Freundlich, Temkin and Dubinin–Radushkevich isotherm equations. The results revealed that the best fit model of adsorption closely followed Langmuir adsorption. Based on adsorption isotherm models, thermodynamics parameters ΔG, ΔH and ΔS were calculated. The negative value of ΔG and ΔH revealed that adsorption process was exothermic, spontaneous and physical. The present work suggests that through simple process hydrothermally modified fly ash has the potential to be used as cost-effective and efficient adsorbent for the treatment of wastewater from textile industries.     

Environmental and economic viability of Alkali Activated Material (AAM) comprising slag,fly ash and spent coffee ground

ABSTRACT

This paper presents a concept of reusing spent coffee ground (CG) as a construction material. Through creating a CG-filled Alkali Activated Material (AAM) with industrial wastes such as fly ash (FA) and slag (S), a strong recycled material was synthesised and found suitable to be used as a road subgrade fill material. Potential groundwater contamination tests were done in accordance to the Australian Standard Leaching Procedure (ASLP). The environmental analysis done on this green material shows that albeit being composed of various industrial wastes and chemicals, CG-filled AAMs in the ground will not cause adverse environmental impacts to surrounding soils and groundwater. Heavy metals and cyanide leached from the AAMs were well below hazardous thresholds. Comparing the carbon footprint of CG, it is found that recycling CG into a construction material would reduce the nett global carbon emission by reducing dependency on quarried material. Cost analyses done on CG-filled AAMs show that these AAMs are expensive to produce relative to traditional construction materials. However, as recycling technology is progressively advancing, in the future the economic value of CG-filled AAM may increase to match those of contemporary construction materials.     

Sidestream tobacco smoke constituents in indoor air modelled in an experimental chamber— Polycyclic aromatic hydrocarbons

Exposure to sidestream tobacco smoke is concerned with constituents in suspension in the indoor atmosphere. The natural dissipation of sidestream tobacco smoke has been investigated in a static atmosphere in a 10 m³ experimental chamber, and the rate of dissipation is expressed as T_0.5, the half-life of residence in the air. Respective T_0.5 of smoke components are calculated from the various sample data points, assuming a kinetic equation of the first-order process. Sidestream smoke has been generated by a smoking machine according to the Coresta standard protocol and then left to age over an 8-hour period, with subsequent sampling at defined time intervals. The experiments have been repeated over five days, and eight data point samples are obtained for each experiment. Besides nicotine, CO, and smoke particulate matter, interest has been focused on polycyclic aromatic hydrocarbons (PAH). The initial concentrations, C₀ for smoke particulate matter and nicotine (gas and particulate phases) are found to be 13.8 mg and 92 μg per cigarette per cubic meter, with T_0.5 being 2.6 and 2.1 hours, respectively. Low molecular-weight PAH have T_0.5 up to 20 hours, explainable only by their high concentrations in the gas phase, while the 3- to 7-ring PAH have T_0.5 of about 2 hours. The contribution of CO to ambient concentration is 91 mg per cigarette per cubic meter. The data can be useful in mathematical modellization studies regarding ventilation or exposure to sidestream smoke.     

Delineation of groundwater contamination around an ash pond: geochemical and GIS approach

The study has investigated the levels of metal contamination in groundwater due to particulate matter fallout and leaching from ash pond and assigned contamination indices for the adjacent localities around an ash disposal site with application of geographic information systems (GIS). Fe, Ba, Cu, Mn, S, Pb, V, and Zn were found to be the major contaminants in groundwater. Enrichment factors (EF) of these elements with respect to the United States Environmental Protection Agency (USEPA) maximum contaminant levels show high values for Mn, Fe, and Pb in groundwater. The zone of attenuation for Ba, Fe, Cu, Mn, S, and Zn in groundwater is about 600-900 m from the ash pond, while Pb did not show any significant attenuation even at a distance of 1200 m. Tube wells around Rankasingha and Kukurhanga villages are most contaminated whereas open wells of Lachhmanpur, Kaniapada, and Kurudul villages showed higher degrees of contamination.     

Estimation of radon exhalation rate, natural radioactivity and radiation doses in fly ash samples from Durgapur thermal power plant, West Bengal, India

Coal and its by products often contain significant amounts of radionuclides, including uranium which is the ultimate source of the radioactive gas radon. Burning of coal and the subsequent emission to the atmosphere cause the re-distribution of toxic trace elements in the environment. Due to considerable economic and environmental importance and diverse uses, the collected fly ash has become a subject of worldwide interest in recent years. In the present study, radon exhalation rate and the activity concentration of (238)U, (232)Th and (40)K radionuclides in fly ash samples from Durgapur thermal power plant (WB) have been measured by "Sealed Can technique" using LR-115 type II detectors and a low level NaI (Tl) based gamma ray spectrometer, respectively. Radon exhalation rate varied from 360.0 to 470.0 mBq m(-2)h(-1) with an average value of 406.8 mBq m(-2)h(-1). Activity concentrations of (238)U ranged from 84.8 to 126.4 Bq kg(-1) with an average value of 99.3Bqkg(-1), (232)Th ranged from 98.1 to 140.5 Bq kg(-1) with an average value of 112.9 Bq kg(-1) and (40)K ranged from 267.1 to 364.9 Bq kg(-1) with an average value of 308.9 Bq kg(-1). Radium equivalent activity obtained from activity concentrations is found to vary from 256.5 to 352.8 Bq kg(-1) with an average value of 282.5 Bq kg(-1). Absorbed gamma dose rates due to the presence of (238)U, (232)Th and (40)K in fly ash samples vary in the range 115.3-158.5 nGy h(-1) with an average value of 126.4 nGy h(-1). While the external annual effective dose rate varies from 0.14 to 0.19 mSv y(-1) with an average value of 0.15 mSv y(-1), effective dose equivalent estimated from exhalation rate varies from 42.5 to 55.2 microSv y(-1) with an average value of 47.8 microSv y(-1). Values of external hazard index H(ex) for the fly ash samples studied in this work range from 0.69 to 0.96 with a mean value of 0.77.     

Leaded gasoline — A cause of cancer

In the course of earlier tests the authors had found that the cancer mortality among 231 adult persons living adjacent to an automobile road was much higher than among persons living in a traffic-free section of the same town. Fifty-nine of the above individuals residing adjacent to the automobile road had been treated with calcium EDTA to eliminate lead. Only one of these later died of cancer. Of the persons who were not treated with calcium EDTA, on the other hand, 30 died of cancer, or ten times more percentage-wise.The existence of small lead deposits as well as the health-impairing effect of lead were demonstrated by measurements of lead and delta-aminolaevulinic acid in urine. After treatment with calcium EDTA, the lead content, as well as the amount of delta-aminolaevulinic acid, became normal. The concentrations of lead were found to be greater in suspended dust particles and in sediment dust along the automobile artery than elsewhere in the town.These findings, together with many other reports in the medical literature lead to the suspicion that lead in automobile gasoline, combined with other carcinogenic substances in automotive exhaust gases, increases the incidence of cancer.     

The infinite-lived rat—An equal-age replacement process

Equal-age replacement is used to formulate the competing-risk problem in terms of a set of nonhomogenous Poisson processes whose mean value functions are the set of cumulative hazards (the integrals of the age-and cause-specific incidence rates). Cumulative hazard is estimated by a weighted count that is the sum of the reciprocals of numbers at risk at the times of occurrence of the specific risk. Occurrence data are generally insufficient to distinguish between plausible forms of the distribution function or types of nonparametric shifts with dose. More emphasis has to be given to understanding the biological mechanisms that dictate the parametric form to be fitted to the data.     

Design of high intensity ionizer—electrostatic precipitator systems

This paper presents the results of a comprehensive set of analytical and experimental studies concerning the application of high intensity ionization technology to retrofit a flyash electrostatic prepitator.Described in detail are the computer-aided methods of performing functional design for ionizer-precipitator systems, selected results of ionizer-precipitator flow model tests, and the chosen physical retrofit. Also presented is the projected performance of an ionizer-precipitator system, derived from two independent design procedures which take into account the effect of space charge and gas velocity distribution on system performance.Results of these studies confirm that high intensity ionizer technology can be applied to significantly improve the collection efficiency of conventional wire-plate electrostatic precipitators.     

Swedish nutrient reduction policies: an evaluation of cost-effectiveness

Since more than 30 years, the Swedish government as well as other governments in the drainage basin strives toward a reduction in nutrient loads to Baltic Sea coastal waters in order to combat eutrophication of the sea. In spite of this, the cost-effectiveness of actual environmental policy for meeting Baltic Sea nutrient targets has not been evaluated by national or international bodies in the region. The aim of this paper is to evaluate Swedish national nitrogen and phosphorus policies with regard to cost-effectiveness. This is done through a comparison of nutrient measures implemented through environmental policy decisions 1995–2005 with cost-effective policies for present national as well as Baltic Sea Action Plan (BSAP) targets. The cost-effective measures are calculated using an empirical programming model including all countries adjacent to the Baltic Sea. Calculations show that measures that jointly reduce nitrogen and phosphorus are hardly applied in actual policy and that reductions in the agricultural sector are much smaller than is cost-effective. Data show, surprisingly, that considerable reductions have been carried out in the Bothnian Sea catchment in spite of there being no nutrient reduction target for this catchment. Results suggest also that the Swedish costs for meeting the new and geographically more restricted targets under the BSAP can be reduced if a policy with less restrictions on the location of phosphorus abatement is applied, compared to what is now suggested.     

Exposure to radon in Swedish dwellings — Attitudes and elimination

Owners of 208 dwellings with radon daughter concentrations of 400 Bq/m³ EER or above were asked about attitudes and measures toward elimination via mailed questionnaires. The response rate was 88% and some steps toward elimination had been taken in 83 dwellings. For the remaining houses, no improvements had been made either because of financial problems, lack of technical advice, or doubts about radon daughter exposure as a health hazard. The results of this study suggest the need to more definitely assess the risk through epidemiologic studies, as well as to provide more information about technical solutions and financial support to house owners.