1,720,964 research outputs found
Sustainable landfilling: hybrid bioreactors and final storage quality
Get PDFModern landfilling constitutes an unavoidable final step in solid waste management. It aims to close the “Material Cycle” bringing elements back to the non-mobile state they were in before their extraction. At the same time, the application of Sustainability Principle to landfills prescribes to guarantee environmental protection and health safety, ensuring that the disposed waste will be chemically and biochemically stable within a reasonable amount of time. A “Sustainable Landfill” must combine these two fundamental purposes, balancing the efforts to obtain a “sustainable closure of material loop”.
The enhancement of biochemical processes in a landfill, with the purpose of reaching faster environmentally safe conditions and terminate the post closure care, is one of the main debated topics in waste management scientific literature. The general aim of the PhD project was giving a contribution to this debate through the lab-scale testing of systems able to simulate landfills behaviour and the analysis of the long-term expectable chemical status of waste undergone to sustainable landfilling.
The first part of the work is an overview on the basic biochemical processes in landfills and on the laboratory-scale landfill simulation tests. The approach used by the PhD student is mainly experimental, starting from the design and the management of several laboratory-scale landfill simulation tests. The elaboration of the obtained data was useful for evaluating the performances of the tested bioreactor concepts as well as for comparing the results to other scientific data derived from a thorough bibliographic research. The original work produced by the student can be subdivided in three different arguments.
The Semi-aerobic, Anaerobic, Aerated (S.An.A. ®) hybrid bioreactor is an innovative landfill concept, lab-scale run with promising results concerning the enhancement of methane production and the reduction of the long-term emissions.
The effects of the recirculation of reverse osmosis leachate concentrate inside the landfill have been analysed to check if the potential accumulation of contaminants in waste body can turn this practice unsustainable.
The Final Storage Quality (FSQ) procedure, for endorsing the landfill Post Closure Care termination, was tested on an over-stabilized waste of which total emissions and chemical speciation of main elements were calculated.Il moderno sistema di deposito finale dei rifiuti in discarica costituisce un passaggio inevitabile nella gestione dei rifiuti solidi. Il suo scopo è chiudere il “ciclo della materia” riportando gli elementi allo stato di immobilità in cui erano prima di essere estratti. Contemporaneamente, l’applicazione del principio di sostenibilità alle discariche prescrive di garantire la salvaguardia ambientale e della salute, assicurando che il rifiuto smaltito diventi chimicamente e bio-chimicamente stabile entro un tempo “ragionevole”. Una “Discarica Sostenibile” deve combinare questi due principi, bilanciando i contributi per ottenere una “chiusura sostenibile del ciclo della materia”.
Il potenziamento dei processi biochimici in discarica, con lo scopo di raggiungere più velocemente condizioni che garantiscano la salvaguardia ambientale e terminare la fase di post-chiusura, è uno degli argomenti più dibattuti nella letteratura scientifica inerente alla gestione dei rifiuti. Lo scopo generale del progetto di dottorato è stato contribuire a questo dibattito, mediante lo svolgimento di test in scala di laboratorio utili a simulare l’andamento dei processi in discarica e analizzando lo stato biochimico finale dei rifiuti trattati.
La prima parte del lavoro consiste in una panoramica sui processi biochimici in discarica e sulla metodica dei test biochimici in scala di laboratorio. L’approccio usato dallo studente in questa tesi è principalmente sperimentale, basato sulla progettazione, l’esecuzione e la rielaborazione dei dati di svariate simulazioni di discarica in laboratorio. La discussione dei risultati ottenuti è stata propedeutica alla valutazione delle performance dei modelli concettuali testati così come al confronto con altri risultati ottenuti grazie a una approfondita ricerca bibliografica. Il lavoro originale svolto dallo studente può essere diviso in tre progetti principali.
Il reattore ibrido Semi-aerobico, Anaerobico, Aerato (S.An.A ®) è una concetto innovativo testato in scala di laboratorio con promettenti risultati per quanto concerne la stimolazione della produzione di metano e la riduzione delle emissioni di lungo termine.
Gli effetti del ricircolo del concentrato di percolato da osmosi inversa all’interno del corpo rifiuti di una discarica sono stati analizzati per verificare se possano esistere potenziali accumuli di contaminanti che rendano insostenibile tale pratica.
La procedura di Final Storage Quality (FSQ) per determinare la chiusura della fase di aftercare di una discarica è stata testata su un rifiuto sovra-stabilizzato di sui sono state calcolate emissioni totali e la speciazione chimica degli elementi principali
Reverse osmosis concentrate recirculation in lab scale anaerobic and aerobic simulation reactors
No full textBiogas production enhancement using semi-aerobic pre-aeration in a hybrid bioreactor landfill
No full textLandfilling continues to be one of the main methods used in managing Municipal Solid Waste (MSW) worldwide, particularly in developing countries. Although in many countries national legislation aims to reduce this practice as much as possible, landfill is a necessary and unavoidable step in closing the material cycle. The need for innovative waste management techniques to improve landfill management and minimize the adverse environmental impact produced has resulted in an increasing interest in innovative systems capable of accelerating waste stabilization. Landfill bioreactors allow decomposition kinetics to be increased and post-operational phase to be shortened; in particular, hybrid bioreactors combine the benefits afforded by both aerobic and anaerobic processes. Six bioreactor simulators were used in the present study: four managed as hybrid, with an initial semi-aerobic phase and a second anaerobic phase, and two as anaerobic control bioreactors. The main goal of the first aerated phase is to reduce Volatile Fatty Acids (VFA) in order to increase pH and enhance methane production during the anaerobic phase; for this reason, air injection was stopped only when these parameters reached the optimum range for methanogenic bacteria. Biogas and leachate were constantly monitored throughout the entire methanogenic phase with the aim of calibrating a Gompertz Model and evaluating the effects of pre-aeration on subsequent methane production. The results showed that moderate and intermittent pre-aeration produces a positive effect both on methane potential and in the kinetics of reaction
Geotechnical and biochemical studies on pre-treated MSW produced in central Italy.
No full textPre-treatments of Municipal Solid Waste (MSW) are common in all developed countries. Thanks to Mechanical Biological Treatments (MBT) it is possible to separate the recyclable waste, the high calorific fraction for energy recover, the organic fraction for biological stabilization and, finally, the stabilized fraction that has to go into the landfill. The purpose of this work is to study some geotechnical and biochemical aspects of four final fractions resulting from MBT of MSW, in order to outline waste managing strategies in relation to typology and impact of the pretreatments. After a trade analysis, tests were performed on compressibility, biological stability and leachability of the main contaminants. Analyses confirm that the stabilized fine fraction (here referred as under-sieve) is more suitable for storage in landfill, while the gross fraction (here referred as over-sieve) is characterized by higher calorific power
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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