1,720,957 research outputs found
Tannery sludge valorization through zeolite-assisted anaerobic process for short-chain fatty acids (SCFAs) production
No full textTannery sludge, a challenging waste, was utilized as a substrate for the production of Short-Chain Fatty Acids (SCFAs) through a series of six thermophilic Continuous Stirred-Tank Reactor runs. The sludge was subjected to a mild thermal pre-treatment and incorporated zeolites (chabazite in run II, and clinoptilolite in run III) in the acidification process. Results highlighted zeolites' impact on chromium concentration and the SCFAs/CODSOL ratio. Ammonia release remained consistent at around 47 % and 51 % for run I and II, respectively, but surpassed 60% in run III, suggesting limited zeolite effectiveness in NH4 absorption. Chromium release in the liquid fraction, due to thermal pretreatment, reached 335 mg/L. While in tests without zeolite, complete removal proved challenging, in zeolite-amended runs, complete removal was achieved, showcasing the materials' heavy metal absorption capacity. SCFA concentrations reached 20260 mgCOD/L, with acidification efficiency varying; runs I and III had ratios around 0.70 COD/COD, while run II showed substantial improvement (0.92) with chabazite. Anaerobic fermentation-digestion mass balance indicated a 41% reduction in landfill sludge mass, reducing its environmental footprint while yielding valuable byproducts like biogas and SCFAs. These findings underscore zeolites' potential in heavy metal absorption and acidification process enhancement, paving the way for applications with tannery sludge
Anaerobic digestion of tannery sludge and tannery waste: a systematic review
No full textThis review investigated the application of anaerobic digestion (AD) as a sustainable solution for managing waste generated by the leather industry and sludge from the treatment of tannery effluents. The novelty of this review is the classification and discussion of the application of AD for both sludge and solid tannery waste, either as mono- or co-digestion with other substrates. The review underscored the potential of AD as a sustainable management of tannery waste and sludge, highlighting the feasibility of AD application to address the environmental challenges of the tanning industry. The application of AD represents a promising perspective in the leather industry, due to the specific nature and the high production volumes of tannery waste and sludge. The review highlighted the impacts of tannery sludge and waste origin and characteristics on biogas yields and digestion performance. The review also indicated the limited experience on mono-digestion of tannery sludge and tannery waste, and the key challenges as process instability, the seasonal variability of feedstock and the potential inhibition due to the presence of heavy metals. Co-digestion with other substrates was identified as a promising approach to improve efficiency and yields, as well as an opportunity to stimulate the implementation of AD in the tannery sector. The experiences on AD of tannery sludge and waste remain largely at laboratory scale, and this can hinder the scale-up of applications. The review discussed the research which made substantial contributions in this area and examined the treatment opportunities for a better understanding of the topic.This study was funded by the European Union – NextGenerationEU, in the framework of the iNEST – Interconnected Nord-Est Innovation Ecosystem (iNEST ECS_00000043 – CUP H43C22000540006).Environmental Technology Review
Single-cell proteins polyhydroxyalkanoates-rich microbial biomass from municipal and winery waste as potential additive for aquafeeds
Full text linkThis study evaluated single-cell protein production from PHA-rich mixed microbial cultures obtained from fermentation and subsequent PHA storage, using urban (namely food waste and municipal sewage sludge; FW-MSS) and agricultural waste (namely wine lees; WL) streams as substrates. FW-MSS fermentation achieved stable short-chain fatty acid (SCFA) production and a high CODSCFA/CODSOL ratio of 0.77 ± 0.01, which allowed to select a mixed microbial culture (MMC) with intracellular PHA content of 15.1 wt%, which aligns with fish dietary standards and yielded a MMC biomass with a protein level of 55.1 wt% and a balanced essential amino acid (EAA) profile. In contrast, WL fermentation showed lower SCFA content and stability, yielding a MMC with 45.8 wt% of protein along with a high non-conformance rate (53.65 %), and 7.2 wt% PHA, making the resulting MMC more suited as a supplemental protein source. Distinct microbial communities developed in the two SBRs due to different feedstocks, influencing the abundance of PHA-storing bacteria, with no known fish pathogens detected in either sample. Statistical analysis confirmed FW-MSS's superior product consistency, supporting its potential as a good quality SCP for aquafeed, especially for rainbow trout, as confirmed by its high essential amino acid index (EAAI)
Minimizing tannery sludge in landfilling through a mixed microbial culture approach: Effect of oxidizing pretreatment, temperature and hydraulic retention time on process performances and chromium fate
Full text linkExploiting tannery sludge as potential source of short-chain fatty acids (SCFAs) and biogas offers a promising solution for a new management of this waste, which is currently landfilled due to chromium presence. This study assessed the optimal hydrogen peroxide (H2O2) dosage, temperature (T) and hydraulic retention time (HRT) through hydrolysis and acidification tests to maximize SCFAs production and to recover biogas from the solid- rich fermentation residue.
A dosage of 0.4 g H2O2/g TS and mesophilic T (40 ◦C) were the most suitable conditions to promote sludge biodegradability and SCFAs production in batch tests. Afterwards, among the two investigated HRT (4 and 8 days) in the semi-continuous processes, longer HRT increased SCFAs concentration and acidification yield up to 16.0 g CODSCFAs/L and 0.32 g CODSCFA/g VS0, respectively. Chromium was initially released in the liquid phase, but completely removed in less than 5 HRTs, allowing the utilization of fermentation liquid without environmental-safety issues. Finally, the solid-rich residue showed its potential as biogas source, having a spe- cific gas production (SGP) of 0.48 m3/kg VS. According to the mass balance assessment, more than 50% of sludge can be saved from landfill, with potential economic benefit close to 2,700,000 €/y compared to the current management practice
Exploiting Tannery Sludge as Renewable Resource for Biogas and Short-chain Fatty (SCFAs) Acids Production
Full text linkThe tannery industry is a very lucrative and widespread sector in Italy, and it is yet one of the most polluting, mainly due to the tannery sludge’s disposal in landfills, as it is considered a special residue by Italian legislation. An evaluation of the performance of the anaerobic fermentation process to obtain biogas and short-chain fatty acids (SCFAs) has been performed in this paper in different conditions concerning temperature, total solids content, and oxidizing and/or thermal pretreatments. The batch test trials revealed that the hydrogen peroxide pretreatment proved to be effective in increasing the biogas production, already at low doses but reaching the highest amount of 204 mL with the dose of 0.6 g H2O2/gTS. Regarding the SCFAs production, the combined microwave and hydrogen peroxide (MW-H2O2) pretreatment followed by thermophilic conditions gave the best results, with maximal SCFA concentration above 24 g CODSCFA/L.
In the tests conducted without pretreatment, the mesophilic temperature seem preferable since the acidification performances were comparable to or even better than their thermophilic counterparts while being less energy intensive. The obtained results proved that tannery sludge can be employed in different ways and provide a viable alternative to landfilling, to handle this waste in a greener way, in a circular economy approach
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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