1,720,975 research outputs found
Polycyclic aromatic hydrocarbons formation in sludge incineration by fluidised bed and rotary kiln furnace
No full textPolycyclic Aromatic Hydrocarbons (PAHs) are typical pollutants arising from incineration. They are produced in any incomplete combustion principally due to inhomogeneities in a combustion chamber. The effects of the afterburning temperature on PAHs formation during sewage sludge incineration are discussed in this paper. Tests were performed inside the area of the wastewater treatment plant of 'Bari Ovest' on a demonstrative plant (maximum throughput 250 kg hr(-1) of dewatered sludge at 20% solids concentration) equipped with a fluidised bed furnace (FBF) and a rotary kiln furnace (RKF) where sewage sludge was fed, either as it was taken from the dewatering section of the wastewater treatment plant, or previously spiked by different dosages of chlorinated hydrocarbons. Exhaust gases were sampled before the bag filter, where the pollutants can be considered representative of those arising from the process. Parallel sampling of flue gas at the stack was also carried out. In the FBF tests with sludge spiked with high dosages of chlorinated hydrocarbons highest values of PAHs concentrations (> 3.9 mug Nm(-3)) were detected before filtration, when the afterburning chamber was not in use. The operation of the afterburning chamber, at a temperature higher than 900degreesC, allows to partially suppress PAHs formation up to values of 0.9 - 3.2 mug Nm(-3). PAHs removal efficiency of the exhaust gas treatment was calculated with a mean value for all the test of 72%. In RKF tests PAHs displayed much lower values before filtration ( range 0.04 - 2.98 mug Nm(-3), mean value 0.51 mug Nm(-3)) probably due to the longer gas residence time in the furnace (> 6 s in comparison with values < 2 s in fluidised bed furnace). Surprisingly, for RKF tests PAHs removal efficiency of gas treatment appeared quite unstable: some tests evidenced PAHs stripping in the scrubber, where the effluent of the wastewater treatment plant was used. No correlation was observed in RKF tests between PAHs concentration before the bag filter and the temperature of the afterburning chamber
Mass and energy balances of sludge processing in reference and upgraded wastewater treatment plants
No full textThis paper describes the preliminary assessment of a platform of innovative upgrading solutions aimed at improving sludge management and resource recovery in wastewater treatment plants. The effectiveness of the upgrading solutions and the impacts of their integration in model reference plants have been evaluated by means of mass and energy balances on the whole treatment plant. Attention has been also paid to the fate of nitrogen and phosphorus in sludge processing and to their recycle back to the water line. Most of the upgrading options resulted in reduced production of dewatered sludge, which decreased from 45 to 56 g SS/(PE × day) in reference plants to 14-49 g SS/(PE × day) in the upgraded ones, with reduction up to 79% when wet oxidation was applied to the whole sludge production. The innovative upgrades generally entail an increased demand of electric energy from the grid, but energy recovery from biogas allowed to minimize the net energy consumption below 10 kWh/(PE × year) in the two most efficient solutions. In all other cases the net energy consumption was in the range of -11% and +28% of the reference scenarios
Dioxins and furans formation in pilot incineration tests of sewage sludge spiked with organic chlorine
No full textThe factors affecting polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) formation were studied in sewage sludge incineration tests carried out on a demonstrative plant. The plant includes a circulating fluidised bed furnace (FBF) and a rotary kiln furnace (RKF), operating alternatively. During the tests sewage sludge was spiked with chlorinated hydrocarbons and the operating parameters of the afterburning chamber were varied. PCDD/F were sampled in each test before the bag filter, thus collecting the above contaminants before abatement systems. From the tests it appeared that PCDD/F were always produced in more abundance in the tests carried out by FBF than by RKF. The higher PCDD/F concentrations in the tests by FBF were reached when sewage sludge was spiked with a high dosage of a surrogate organic mixture of chlorinated hydrocarbons and when the afterburning chamber was used only as transit equipment with the burner off. The distribution of the different PCDD/F homologues was compared. P(5)CDFs were generally the prevalent fraction, with very few exceptions for the tests by RKF at high temperature of the afterburning chamber. As for FBF tests, it was found that the PCDD/F homologue profile depends on the afterburning chamber temperature. (C) 2003 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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