1,720,963 research outputs found
Biological nitrification: heavy metal inhibition and biomass adsorption
No full textThe present work deals with an experimentation performed in batch reactors to evaluate copper inhibition in the biological nitrification process. The inhibition was measured both directly, through AUR (ammonia uptake rate) measurement and indirectly, through sOUR (specific oxygen uptake rate) tests. Results show that, due to the essential role of small copper amount for the metabolism of organic matter, nitrifying microorganisms activity was dramatically inhibited only at a copper concentration higher than 1 mg/l. A good fitting of the AUR inhibition data was then obtained by the Kroiss model.
Comparing the inhibition data obtained through AUR and sOUR tests, results show that he respirometric tests (sOUR) showed an higher degree of inhibition (up to 50%) with respect to the AUR tests, due to the small oxygen consumption that in the nitrification reaction occurred.
In addition, experimental tests performed to evaluate copper distribution between the liquid and solid phases, showed that, up to a concentration of 5 mg/l, the copper amount in solution or adsorbed onto the biomass accounted about for the 98% of the total copper added, while, at higher copper concentration, because of the increasing formation of chelates and the precipitation of copper salts, this amount accounted for the 70%
A Real Time Toxicity Bioassay for Activated Sludge Reactor
No full textActivated sludge reactor is commonly employed for the secondary treatment of industrial wastewater, showing a high purification yield, operating simplicity and cost-effectiveness. Nevertheless, industrial wastewater generally contain numerous organic and inorganic compounds which are not biodegradable; heavy metals are often found in effluents from electroplating and metal-processing industries, manufacturing of paints, plastics, scientific instruments, salts are found in wastewater from production of pesticides, pharmaceutical and food industry, waste-dump percolating water. Primary treatments are often designed to reduce heavy metal and salt contents in wastewater, nevertheless trace concentrations persist and may reach the biological reactor, resulting in biomass inhibition and dramatic loss in purification efficiency. Respirometry through Oxygen Uptake Rate measurement is one of the most rapid and reliable methods to assess the inhibition of activated sludge. In previous studies toxicity tests for specific compounds have been performed following different procedures and attaining heterogeneous results. In this work a simple modification of the configuration is proposed, in order to assess in real time the toxicity and the inhibiting effect of the incoming wastewater before it reaches the reactor. A sample is drawn from the influent and a respirometric test is performed on mixed liquor collected from the reactor itself. If the inhibition exceeds the limit, the influent is sent to storage and to an alternative treatment. Preliminary experiments were carried out with bench-scale CSTR, supplied with synthetic wastewater. Copper sulphate and sodium chloride were chosen as inhibiting compounds, supplied separately to batch samples of activated sludge in shock load at different concentrations. Copper concentration in the mixed liquor was measured by atomic absorption and salt concentration was determined through conductance measures. Inhibition up to 90% was evaluated by OUR test with short response time, demonstrating the suitability of this tool to a real time toxicity bioassay for activated sludge reactor
Inhibition kinetics of copper on activated sludge process through respirometric tests: experimental validation
No full textEffects of copper shock load on activated sludge process were investigated. Oxygen uptake rate measurements proved to be a rapid and reliable tool to detect inhibition within one hour from the shock load. Four types of kinetic models describing metal inhibition were investigated and employed to fit experimental data. Kinetic parameters were determined by non-linear least square correlations. Both non-competitive and competitive models resulted to provide the most accurate description of copper inhibition
Experimental evaluation of inhibition effects of saline wastewater on activated sludge
No full textIndustrial wastewater often has a high salt content, due to specific factories and to the use of seawater in coastal areas. Once it has reached the activated sludge treatment, saline wastewater may cause biomass inhibition and dramatic loss in purification efficiency. In the present work, the inhibiting effect of saline influent was experimentally evaluated through respirometric tests on samples of the incoming wastewater. Activated sludge was grown in bench-scale continuous flow stirred tank reactor (CFSTR), supplied with synthetic wastewater. Synthetic saline wastewater was prepared using sodium chloride and sodium sulphate at different concentrations. Samples of mixed liquor were drawn from the CFSTR reactor and fed with saline wastewater in shock-load or in continuous mode, then respiration activity and carbon removal yield were evaluated. In batch mode (shock-load), salt/biomass ratios between 0.37 and 30.7 gsalt gVSS -1 gave respiration inhibition between 4% and 84% respectively. The respirometry bioassay required a short response time and the values of respiration inhibition predicted the loss in carbon removal efficiency with a good accuracy. In continuous mode, for salt/biomass ratio of 35.5 gsaltgVSS -1, respiration inhibition of 81% was obtained. This work showed that a relation between inhibition in shockload and inhibition in continuous mode can be determined, therefore, the procedure herein proposed allows performing offline bioassays on real biological plants, to assess in real time the inhibiting effect of the incoming wastewater before it reaches the activated sludge reactor
Experimental validation of a kinetic model for activated sludge process with step sludge recirculation
No full textStep Sludge Recirculation was proposed as multistage configuration to enhance BOD removal with minimal sludge production. SSR proved to be more efficient than conventional multistage at high organic load, resulting in 98% BOD removal with good effluent quality. SSR is assumed to enhance predation phenomena in activated sludge. This assumption was qualitatively verified with a kinetic model
A new method of high-density culture of animal cells for the insudstrial production of biochimical compounds
No full textSCGCGR-53 1092 SB ISIC . Consultable sur demande à la bibliothèque de l'EPFL / Offered in consultation at the EPFL librar
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
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