1,720,959 research outputs found
Biological treatment of hypersaline wastewater in a continuous two-phase partitioning bioreactor. Analysis of the response to step, ramp and impulse loadings and applicability evaluation
No full textThe response of a continuous two-phase partitioning bioreactor (C-TPPB) operated with polymeric tubing treating hypersaline wastewater was investigated under dynamic load conditions of step, ramp and impulse inputs of the influent flow rate. Tests were performed with synthetic wastewater consisting of NaCl (100 g L−1) and 2,4-dimethylphenol (DMP) (∼1200 mg L−1) to simulate the organic fraction. A biomass specifically acclimatized to the compound was utilized in the tests. The experimental system provides separation of the toxic wastewater flowing inside the polymeric tubing (coiled in the bioreactor) from the microbial culture present in the bulk bioreactor phase with the polymer providing permeability to the organic molecules as well as a barrier to salt transport. These features allowed achieving high performance even in the most severe loading conditions. Removal efficiencies >96% were obtained for DMP under all investigated load conditions (i.e. for influent salt and organic loads up to six times the base case load). A DMP mass balance at the end of the dynamic tests showed that 88% of the removed DMP was biodegraded and only 8% was retained into the polymer tubing itself. No significant variation of the DMP concentration in the bioreactor was observed in all cases thus demonstrating the complete removal of the transferred substrate and the effective performance of the biomass, which was not affected by the applied dynamic loads. A comparative analysis of C-TPPB results with the performance data of the classical technologies commonly applied for saline wastewater treatment has been performed to evaluate the system applicability
Solid-liquid partitioning bioreactors applied to the removal of mixtures of phenolic compounds
No full textTreatment of synthetic tannery wastewater in a continuous two-phase partitioning bioreactor. Biodegradation of the organic fraction and chromium separation
No full textA continuous two-phase partitioning bioreactor has been tested for treating a synthetic leather tannery wastewater with the objective of achieving effective removal of the organic load and complete chromium separation. The bioreactor was operated with 5.5 m of Hytrel 8206 polymeric tubing fed with a synthetic tannery wastewater consisting of 4-chlorophenol (concentration in the range of 1000–2500 mg L−1) and potassium dichromate (100 mg L−1 as Cr (VI)), and immersed in a 4 L bioreactor containing the microbial culture acclimatized to the compound. This configuration prevents the direct contact between the toxic wastewater and the microorganisms themselves, and provides the gradual organic substrate delivery through the tubing walls. Abiotic partition and mass transfer tests were performed to investigate the transport of dichromate and 4-chlorophenol across the tubing into the bulk phase of the bioreactor. No appreciable mass transfer of dichromate was detected. During biotic testing, the influent organic load in tubing has been varied in the range of 19–94 mg h−1 and the hydraulic retention time from 3 to 6 h. Achieved biological removal efficiencies were in the range of 89–95% for the highest applied loads. Process kinetics (which included consideration of both mass transfer and biological rates) were evaluated, and it was found that the increased load did not result in any decrease in 4-chlorophenol removal rate. This work has shown that the continuous two-phase partitioning bioreactor has significant potential in enhancing the biological treatment of tannery wastewater, which is a typical representative of industrial “hostile” wastewater
On the applicability of a hybrid bioreactor operated with polymeric tubing for the biological treatment of saline wastewater
No full textEffective biological treatment of high salt content wastewater requires consideration of both salt and organic toxicity. This study treated a synthetic saline wastewater containing NaCl (100 g L− 1) and 2,4-dimethylphenol (1.2 g L− 1) with a hybrid system consisting of a biological reactor containing spiral-coiled polymeric tubing through which the mixed feed was pumped. The tubing wall was permeable to the organic contaminant, but not to the salt, which allowed transfer of the organic into the cell-containing bioreactor contents for degradation, while not exposing the cells to high salt concentrations. Different grades of DuPont Hytrel polymer were examined on the basis of organic affinity predictions and experimental partition and mass transfer tests. Hytrel G3548 tubing showed the highest permeability for 2,4-dimethylphenol while exerting an effective salt barrier, and was used to verify the feasibility of the proposed system. Very high organic removal (99% after just 5 h of treatment) and effective biodegradation of the organic fraction of the wastewater (> 90% at the end of the test) were observed. Complete salt separation from the microbial culture was also achieved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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