1,720,960 research outputs found
Electrical voltage application as a novel approach for facilitating methanogenic granulation
No full textDespite having high-rate methanogenic performance, up-flow anaerobic sludge blanket reactor still has challenges regarding long-start up period (3–8 months) for granulation. In this study, “electrical voltage (EV, 0.3 V) application” was attempted for facilitating granulation in the continuous operation with increased organic loading rates (0.5–11.0 kg COD/m3/d). Up to 11.0 kg COD/m3/d, EV-reactor exhibited the stable performance, while the control failed. After 49 days of operation (at 7 kg COD/m3/d), the granules collected from EV-reactor had larger diameter (2.3 vs 1.6 mm), higher settling velocity (2.6 vs 1.9 cm/s), and higher hydrophobicity (52.1 % vs 34.5 %), compared to the control. EV application also increased the specific methanogenic activity for propionate and hydrogen almost by two times. The relative abundance of Pseudomonas sp. (quorum sensing (QS)-related microbe) in EV-reactor was 17 % higher than that in the control. In addition, EV application increased the expression of QS genes significantly by 27 times.
Enhancement of waste activated sludge hydrolysate digestion efficiency via promotion of direct interspecies electron transfer
No full textAnaerobic digestion (AD) of waste activated sludge (WAS) yields low methane (CH4) because extracellular polymeric substances hinder hydrolysis and limit its biodegradability. Pretreatment methods such as alkaline or mechanical disruption can enhance solubilization; however, the resulting hydrolysate often contains recalcitrant compounds that inhibit further degradation. In this study, a combination of alkali along with ultrasonication was applied to enhance the solubilization of WAS, followed by CH4 production under AD. Pretreated results showed alkaline (pH = 12) + ultrasonication (30 min) showed 300 % higher solubilization compared to ultrasonication (60 min) alone. Batch experiments (with and without Fe3O4) were conducted, and the results showed that pretreated hydrolysate supplemented Fe3O4 showed higher CH4 yield than their control counterparts (up to 85 %). To validate the batch results of pretreated hydrolysate, a continuous operation was conducted without (Control) and with an electric voltage reactor (EVR) at different organic loading rates (OLR) up to 4 g chemical oxygen demand (COD)/L/d. The results showed that EVR enhanced the CH4 production by 28 % and COD removal by 19 % at 4 g COD/L/d compared to the control. Microbial community analysis highlighted the dominance of Syntrophomonas zehnderi (a fatty acid oxidizer) in EVR, which increased by 27 %, suggesting stronger syntrophic partnerships with methanogens. Genetic profiling further supported these findings, showing a 25 % upregulation in Adenosine triphosphatease related genes and a striking 69 % increase in pili-associated genes, both critical for direct interspecies electron transfer. These results demonstrated that the combined pretreatment (alkali + ultrasonication) offers a promising alternative for enhanced AD of WAS.
Enhanced anaerobic treatment of sulfate-rich wastewater by electrical voltage application
No full textTreatment of sulfate-rich wastewater with high methane recovery is a major concern due to sulfide inhibition. Here, an electrical voltage (EV) aims to enhance methanogenesis and sulfidogenesis to treat sulfate-rich wastewater. Two (control and EV-applied) reactors were operated with a gradual decrease in chemical oxygen demand (COD)/SO42− ratios (CSR). EV-applied reactor (EVR) demonstrated an increase of ∼30 % in methane production and ∼40 % in sulfate removal, compared to the control till CSR of 2.0. At CSR 1.0, the control failed, while EVR still exhibited a stable performance of 50 % COD-methane recovery. Microbial community results showed that the relative abundance of sulfate-reducing bacteria in EVR was 1.5 times higher than the control. Furthermore, higher relative abundance of dissimilatory sulfate reductase (>50 %) and Ni/Fe hydrogenase (x15) genes demonstrated an improved tolerance against H2S toxicity. This study highlights the importance of EV application by minimizing the byproduct inhibition in sulfate-rich wastewater. © 2022 Elsevier Ltd
Production of high-calorific biogas from food waste by integrating two approaches: Autogenerative high-pressure and hydrogen injection
No full textAuto-generative high pressure digestion (AHPD) and hydrogen-injecting digestion (HID) have been introduced to directly produce high CH4-content biogas from anaerobic digester. However, each approach has its own technical difficulties (pH changes), and practical issues (high cost of H 2 ) to obtain > 90% CH4 containing biogas, particularly, from the high-strength waste like food waste (FW). To overcome this problem, in this study, AHPD and HID were integrated, which can offset each drawback but maximize its benefit. Substrate concentration of FW tested here was 200 g COD/L, the highest ever applied in AHPD and HID studies. At first, the reactor was operated by elevating the autogenerative pressure from 1 to 3, 5, and 7 bar without H-2 injection. With the pressure increase, the CH4 content in the biogas gradually increased from 52.4% at 1 bar to 77.4% at 7 bar. However, a drop of CH4 production yield (MPY) was observed at 7 bar, due to the pH drop down to 6.7 by excess CO2 dissolution. At further operation, H-2 injection began at 5 bar, with increasing its amount. The injection was effective to increase the CH4 content to 82.8%, 87.2%, and 90.6% at 0.09, 0.13, and 0.18 L H-2/g CODFW.fed of H 2 injection amount, respectively. At 0.25 L H-2/g COD FW.fed, there was a further increase of CH4 content to 92.1%, but the MPY was dropped with pH increase to 8.7 with residual H 2 being detected (4% in the biogas). Microbial community analysis showed the increased abundance of piezo-tolerant microbe with pressure increase, and direct interspecies electron transfer contributors after H-2 injection. In conclusion, the integration of two approaches enabled to directly produce high calorific biogas (90% > CH4, 180 MJ/m(3) biogas) from high-strength FW at the lowest requirement of H-2 (0.18 L H2/g COD FW.fed) ever reported. (C) 2021 Elsevier Ltd. All rights reserved.
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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