1,721,047 research outputs found
Growing microalgae in a “quasi-isoactinic” photobioreactor
Full text linkThe aim of this work is setting up the conditions of an “iso-actinic” photobioreactor that is a photoreactor for the cultivation of microalgae in which the local volumetric rate of photon absorption (LVRPA), can be considered uniform to a good extent. We describe the composition of this cheap photoreactor and how we made it. The system is driven by an Arduino platform that makes it possible to control light intensity as well as light-dark cycles. Preliminary results obtained by growing Nannochloropsis gaditana, a microalga famous for its fat content, in this innovative reactor are presented. We finally observed how microalgae responds to flashing light irradiation
Utilization of native Chlorella strain in laboratory-scale raceway reactor for synthetic wastewater treatment: A study in batch and continuous modes with multi-substrate modeling
Full text linkDespite of the possibility to include microalgae in civil wastewater treatment process, the practice is still not common due to the lack of available instruments to implement it. In this study, a straightforward comprehensive approach for dealing with microalgal wastewater treatment involving an original kinetic model is proposed. A first set of batch cultures of a native strain of Chlorella was firstly carried out to obtain the kinetic parameters: maximum growth factor (μmax) and half-saturation constant (Ks), for each limiting nutrient. Maximum growth factor values of 0.0279 for PO43−, 0.0319 h−1 for NH4+, 0.0352 h−1 for glucose, and 0.0263 h−1 for the overall medium were found. Regarding the Ks, values of 1.08 mg L−1, 27.70 mg L−1, 1.34 mg L−1, were found for PO43−, NH4+ and glucose respectively, and a value of 2.8 % of the total nutrients for the overall medium. These parameters were used to set a multi-substrate kinetic model able to predict the growth in batch and in continuous operation within a laboratory scale raceway reactor. The removal capabilities of the microalgae for each addressed pollutant were evaluated in a batch system and in a continuous system at dilution rates of 0.0025, 0.005, 0.01 and 0.015 h−1. This comprehensive approach represents a significant step towards addressing the continuous treatment of wastewater utilizing microalga
Syngas production from organic fraction of municipal solid waste by supercritical water gasification
No full textInoculum of indigenous microalgae/activated sludge for optimal treatment of municipal wastewaters and biochemical composition of residual biomass for potential applications
Full text linkIn this work, municipal wastewater was treated with microalgal/activated sludge consortia. We aimed at
obtaining a positive interaction between the microalgae and the heterotrophic bacteria and identifying the best
combination for bioremediation purposes. A strain of Chlorella sp CW2 employed in this work was isolated from
AS and molecularly characterised in this work for the first time. This strain and another previously isolated strain
(Chlorella sp Pozzillo) were inoculated alone and in combination with AS in different ratios in wastewaters.
Microalgae/activated sludge growth curves were obtained by using a UV–vis spectrophotometer and a fluorimeter
to distinguish the contribution of the photosynthetic microorganisms to the total growth. The effectiveness
for the bioremediation of municipal wastewaters was evaluated by measuring the COD, the total
nitrogen and total phosphorous content at the end of batch cultivations. Overall, the best abatement was achieved
by the microalga Chlorella sp CW2 inoculated with activated sludge in the ratios 1:2 and 2:1, with a
decrease of 81.39 % ± 0.56, 86.12 % ± 0.43, 82.89 % ± 2.66 and 82.5 % ± 0.83, 72.66 % ± 0,46, 97.15 % ±
0.44 of COD, total nitrogen and total phosphorous, respectively. Finally, the residual biomass, constituted by a
sludge enriched in microalgae, was analysed for its content in carbohydrates, lipids and fatty acid in order to
suggest the best application for its valorisation. Considering the final composition of the obtained biomass and its
remediation potential, the most promising sample may be the microalga Chlorella sp CW2 inoculated with
activated sludge in the ratio 1:5
Kinetic of the Sewage Treatment: The Consumption of Organic Carbon of The Microalga Chlorella sp
Full text linkAs well known, microalgae are eukaryotic or procaryotic microorganisms able to photosynthesize, namely
transforming inorganic substrates and sun light into organic compounds and chemical energy. They result very
promising in treating civil wastewaters thanks to their ability to employ nitrates and phosphates as nutrients
(Lima et al., 2019). Autotrophic microalgae are, anyway, not useful in decreasing the organic carbon content of
wastewaters, and for this reason, they cooperate with heterotrophic bacteria. The usefulness of microalgaebacteria consortia in treating wastewaters and the ratio of their inoculum was investigated in a previous work
(Lima, 2022a). Contrarily to autotrophic microalgae, mixotrophic microalgae are able to decrease the organic
content of the matrix in which they are grown. In this work, we preliminarily investigated the capability of the
autochthonous microalga Chlorella sp. CW2 to grow in mixotrophy and decrease the organic content of the
artificial wastewater in which they are grown. Several batch cultivations were performed with glucose in different
concentrations. Kinetic parameters were obtained and employed to determine the dilution rate (D) ideal for the
abatement of glucose from the artificial wastewater
Experimental and Computational Study of Supercritical Fluid Extraction (SFE) of Omega-3 Components from Fish Oil in Structured Packing
Full text linkThe benefits of polyunsaturated fatty acids and their implications for human health have gained scientific
attention to their extraction from biological sources, not being produced by the human body. Most known
industrial productions of omega-3 fatty acids often work under operating conditions that may degrade these
components and they often use toxic or flammable solvents that can adversely affect human health. In this
sense, innovative and interesting prospects are provided by Supercritical Fluid Extraction (SFE).
In this work, two parallel studies were carried out: an experimental activity in a laboratory apparatus using
supercritical carbon dioxide (scCO2) and preliminary computational fluid dynamics (CFD) simulations, limited to
the hydrodynamic aspects of the process. In the experimental apparatus a Sulzer® EX structured packing, made
up of corrugated metal gauze sheets, was used as the column filler. The study made it possible to identify the
optimal operating conditions leading to an enrichment of the starting mixture in Eicosapentaenoic acid (EPA)
and Docosahexaenoic acid (DHA), target products. CFD simulations were based on the Volume of Fluid (VOF)
approach, suitable to the present complex multiphase system with two phases in close contact (transesterified
fish oil and scCO2). The meatus created by the corrugations of the metal gauze was chosen as the calculation
domain representative of the system. The computations were performed by the commercial software Ansys
Fluent®, which allowed the prediction of the hydrodynamic evolution of the system through transient simulations.
CFD predictions were in qualitative agreement with the experimental result
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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