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Integrated selection of PHA-storing biomass and nitrogen removal via nitrite from sludge reject water: a mathematical model
No full textOne of the most recent innovations to promote a circular economy during wastewater treatment is the production of biopolymers. It has recently been demonstrated that it is possible to integrate the production of biopolymers in the form of polyhydroxyalkanoates (PHA) with nitrogen removal via nitrite during the treatment of sludge reject water. In the present study, simulation of a new process for bioresource recovery was conducted by an appropriate modification of the Activated Sludge Model 3. The process consists of the integrated nitrogen removal via nitrite from sludge reject water and the selection of PHA-storing biomass by inducing a feast and famine regime under aerobic and anoxic conditions. According to the results, it is anticipated that simulation data matched very satisfactorily with the experimental data and confirmed the main experimental observation, showing that during the famine period the PHA depletion was almost complete due to the availability of nitrite as the electron acceptor. Simulation results indicate that the selection of the volumetric organic loading rate and of the relative duration of the aerobic feast/anoxic famine duration is critical in order to allow for the effective denitritation of the internally stored PHA during the famine phase
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
Solid Waste and Wastewater Management in Light of Circular Economy
No full textGuest Editor in Special Issue of the Journal of Environmental Managemen
Biological wastewater treatment with the use of membranes
No full textScarce water resources in several parts of the world have led to an increased interest in wastewater reuse applications and have promoted the development and application of advanced wastewater treatment technologies. The Membrane Bioreactor (MBR) system is an advanced wastewater treatment system which has been adopted the last years for the biological treatment of wastewater instead of the conventional system of Activated Sludge (AS). MBR systems combine biological treatment and membrane filtration for the secondary treatment of wastewater. The membranes are employed in order to separate the final effluent from sludge. Therefore, this system does not employ a secondary sedimentation tank for effluent clarification and consequently the problems of poor sludge settling due to sludge bulking or due to sludge deflocculation are not encountered. Moreover, MBRs achieve a superior effluent quality that is comparable or even superior to tertiary treatment systems as the membranes are an absolute barrier to suspended solids and to colloidal matter. The adoption of MBRs can lift the barriers for the wider adoption of wastewater reuse, since the final effluent meets the stringiest reuse guidelines for unrestricted irrigation, provided that some disinfection is ensured. This is particularly important for countries facing significant water shortage problems such as Greece. The main operational problem associated with MBR systems is that of membrane fouling, which is defined as the gradual deposition of particles at the membrane surface and interior. As the system operates, the transmembrane pressure (TMP) gradually increases for given membrane flux due to membrane fouling. Once the TMP has reached a certain peak value the membrane module must be removed and must be chemically cleaned in order to restore its permeability. A variety of methods are employed during the system operation to limit fouling; these include backwash, coarse bubble-aeration and chemical cleaning at low doses inside the biological reactor. Coarse bubble aeration significantly increases the system's operational cost. However, even with the adoption of these methods fouling gradually builds up and intensive chemical cleaning is required in which case the module is removed from the biological reactor and is placed in a suitable chemical cleaning solution for several hours. The latter method is the most effective for restoring membrane permeability, but shortens the life-time of the membrane and is thus only periodically employed. As it is evident, membrane fouling increases the operational cost of the system. Inevitably, much research has focused on understanding membrane fouling and its mechanisms, on determining the factors that mostly affect it and on determining cost-effective methods for its limitation. Fouling is a highly complex phenomenon which is influenced by several parameters; these can be grouped in four main categories: (1) the membrane properties, (2) the biomass characteristics, (3) the operating conditions and (4) the influent wastewater. The membrane characteristics and the biomass properties directly impact on membrane fouling, while the operating parameters and the influent wastewater mainly influence fouling indirectly through their impact on biomass properties. The main research question that this thesis addresses is the effect of the solids retention time (SRT) and of the sludge properties on membrane fouling. A series of important issues are investigated. These are: • The impact of the solids retention time on biomass properties and consequently on membrane fouling. • The impact of biomass properties on long-term and on short-term membrane fouling. • The dominant fouling mechanisms in both long-term and short-term membrane fouling. • The determination of the dominant fraction of biomass and of extracellular polymeric substances for the solids retention times under investigation. • The impact of the addition of chemical and physical conditioners to sludge in order to minimize membrane fouling. • The heterotrophic and autotrophic biomass activity. • The MBR long-term biological performance. The long-term membrane fouling was investigated through the operation of a pilot scale MBR system for approximately 2,5 years at SRT = 10, 15, 20 and 33 days, while the short-term membrane fouling was investigated with the 60-minute filtration experiments conducted in a batch ultrafiltration system. […][…] Η παρούσα διδακτορική διατριβή έχει ως βασικό στόχο την εξέταση της επίδρασης των λειτουργικών παραμέτρων και των χαρακτηριστικών της βιομάζας στην έμφραξη των μεμβρανών. Η βασική λειτουργική παράμετρος που διερευνάται είναι ο χρόνος παραμονής των στερεών στο σύστημα (θc), ενώ εξετάζεται η επίδραση μιας σειράς ιδιοτήτων της ιλύος στη μακροχρόνια έμφραξη, όπως είναι τα εξωκυτταρικά πολυμερή, τα κολλοειδή, η συγκέντρωση του ανάμικτου υγρού, η διηθησιμότητα και η καθιζησιμότητα της ιλύος. Επιπλέον, στα πλαίσια της παρούσας διατριβής εξετάζεται η επίδραση των χαρακτηριστικών της βιομάζας στη βραχυχρόνια έμφραξη των μεμβρανών. Η μακροχρόνια έμφραξη εξετάζεται με τη συνεχή λειτουργία πιλοτικού συστήματος MBR για διάστημα 2,5 περίπου ετών σε θc = 10, 15, 20 και 33 ημέρες. Η βραχυχρόνια έμφραξη εξετάζεται σε πρότυπο, εργαστηριακό αντιδραστήρα μεμβρανών υπερδιύλισης διακοπτόμενου έργου με διήθηση ιλύος για 60 λεπτά. Παράλληλα, με την εφαρμογή κατάλληλων μοντέλων διήθησης εξετάζονται οι κυρίαρχοι μηχανισμοί έμφραξης, τόσο για τη μακροχρόνια όσο και για τηβραχυχρόνια λειτουργία και εξετάζεται κατά πόσο οι μηχανισμοί αυτοί είναι ταυτόσημοι. Επίσης, εξετάζονται τα κυρίαρχα κλάσματα του ανάμικτου υγρού και των εξωκυτταρικών πολυμερών για τις υπό διερεύνηση λειτουργικές συνθήκες, καθώς και η επίδραση της προσθήκης συγκεκριμένων ουσιών (φυσικών ορυκτών, κροκιδωτικών και κατιονικού πολυμερούς) στη βιομάζα με στόχο τη μείωση της έμφραξης. Η εξέταση της επίδρασης των προσθέτων στη μείωση της έμφραξης πραγματοποιείται στον εργαστηριακό αντιδραστήρα μεμβρανών υπερδιύλισης. Τέλος, εξετάζεται η δραστηριότητα της ετεροτροφικής και αυτοτροφικής βιομάζας καθώς και οι γενικότερες βιολογικές λειτουργίες του συστήματος MBR. […
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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