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The ANAMMOX process as the second step for the treatment of ammonium rich refinery wastewater with high Corg/N ratio
No full textThe combination of partial nitritation and anammox (anaerobic ammonium oxidation) has been mainly applied to the treatment of wastewaters with high ammonium concentration and low content of biodegradable organic carbon. So far, only few studies have focused on the application of partial nitritation-anammox process to the treatment of ammonium-rich wastewaters characterized also by a high organic carbon to nitrogen ratio (Corg/N), as well as by the presence of toxic substances: in this study, an anammox reactor was started-up and fed with the effluent from a partial nitritation reactor treating IGCC (Integrated Gasification Combined Cycle) wastewater, in order to evaluate its feasibility as an alternative to the currently applied chemical-physical-biological treatment.
A sequencing batch reactor was inoculated with granular anammox biomass and run at controlled temperature (35±0.5 °C) and pH (7.7±0.3). The synthetic influent containing NH4-N (up to 250 mg/L) and NO2-N (up to 330 mg/L) was progressively replaced by the IGCC wastewater, which had been pre-treated in the lab-scale partial nitritation reactor. When the reactor was fed with the synthetic medium at the target nitrogen loading rate (NLR, 0.350 gN/L·d), the observed NH4-N removal efficiency was 93±5%, and no nitrite was detected in the effluent. Good overall process performance was maintained as increasing amounts (up to 65%) of the effluent from the partial nitritation system were fed to the anammox reactor: NH4-N and NO2-N removal efficiencies were 98.9±1.0% and 96.6±2.1%, respectively, and nitrite specific removal rate peaked at 0.28 gNO2-N/gVSS∙d. On day 154, a nitrogen shock load was applied to evaluate anammox stability during start-up: despite system sensitivity to the sudden increase of nitrogen load, process performance was recovered and the percentage of IGCC wastewater in the influent could be raised to 100% with fairly good NH4-N and NO2-N removal efficiencies (85.7±5.8% and 88.2±2.3%, respectively). Anammox granules were compact (diameter, 636±20 m) and dense (86.5±3.4 gTSS/Lgran), with good settling properties. The total organic carbon (TOC) removal efficiency was low: since most of TOC (around 80±8%) had been removed in the preliminary partial nitritation step (results not shown), it can be assumed that the residual TOC entering the anammox reactor was slowly biodegradable, therefore heterotrophic denitrifiers did not compete with anammox biomass for nitrite.
The results indicate that anammox start-up can be successfully achieved and the process can be applied in combination with a preliminary partial nitritation step for the treatment of ammonium-rich IGCC wastewater, thus providing useful information also for the treatment of similar wastewaters with high Corg/N ratio and containing toxic substances
Trattamento di reflui petrolchimici con fanghi aerobici granulari: effetti della concentrazione del substrato di crescita
Full text linkIl processo a fanghi attivi per il trattamento biologico dei reflui mostra scarsa tolleranza alle fluttuazioni di carico ed è sensibile alla presenza di sostanze tossiche, anche in basse concentrazioni. I sistemi a fanghi aerobici granulari sono caratterizzati da notevole flessibilità, ridotti consumi energetici, elevata sedimentabilità dei fanghi, maggiore resistenza alle sostanze tossiche contenute nei reflui, e sono in grado di trattare elevati carichi organici volumetrici. Tra i reflui industriali, quelli petrolchimici presentano un’estrema variabilità, che deriva dalle numerose tipologie di processo applicate nei diversi impianti. Nello studio proposto si è valutata la trattabilità in un reattore a fanghi granulari (GSBR, granular sludge sequencing batch reactor) di un refluo petrolchimico ad alto tenore di azoto ammoniacale (N-NH4+) prodotto dal ciclo combinato di gassificazione integrata (IGCC), con l’obiettivo di sostituire o integrare il sistema di trattamento attualmente impiegato in raffineria. Per favorire la granulazione, è stato aggiunto nell’influente un substrato organico rapidamente biodegradabile (acetato), il cui dosaggio è stato progressivamente ridotto, e infine sospeso, per ridurre i costi operativi nell’ottica di un’eventuale applicazione del sistema a scala reale. Le prestazioni del processo in termini di efficienze di rimozione di N-NH4+ e sostanza organica (espressa come carbonio organico totale, TOC) sono state buone (rispettivamente 70% e 90%) in condizioni di carico organico elevato, e si sono mantenute tali (così come le caratteristiche morfologiche e di sedimentabilità dei granuli) anche dopo la sospensione del dosaggio di acetato. I risultati hanno dimostrato che: (i) il GSBR può rappresentare una valida alternativa per il trattamento del refluo IGCC; (ii) l’apporto di acetato può essere sospeso una volta completato l’avviamento del GSBR; (iii) la conseguente riduzione dei costi operativi rende interessante l’applicazione del processo a scala reale
The start-up of an anammox reactor as the second step for the treatment of ammonium rich refinery (IGCC) wastewater with high C org /N ratio
Full text linkIn this study, the refinery wastewater produced by the integrated gasification combined cycle (IGCC) and pre-treated in a lab-scale partial nitritation chemostat was fed to a granular anammox reactor, in order to evaluate its feasibility as the final treatment step. The IGCC wastewater was characterized by high NH4-N concentration (540±82 mg L-1), high organic carbon to nitrogen ratio (Corg/N), and by the presence of toxic substances. A conservative exponential law was adopted to progressively replace the synthetic influent with the pre-treated IGCC wastewater, in order to avoid any stressful conditions which could hinder the process. An increase in specific anammox activity (SAA) up to 0.104 gNO2-N gVSS-1 d-1 was initially observed, suggesting that stimulation may occur if pre-treated IGCC wastewater dilution is sufficiently high. A system malfunction caused a worsening of process performance, which was partially restored: when only pre-treated IGCC wastewater was fed, the nitrogen removal efficiency and SAA were 71±3% and 0.045±0.002 gNO2-N gVSS-1 d-1, respectively, and the removal of organic matter due to denitrification was negligible. As to physical/morphological properties of anammox granules, they did not change significantly during the whole experimental campaign. Results showed that the anammox process can be successfully applied to treat complex industrial wastewaters with high Corg/N ratio, if a conservative start-up strategy is adopted and the preliminary partial nitritation step guarantees an efficient removal of readily degradable organic matter
Application of anammox within an integrated approach to sustainable food waste management and valorization
Full text linkIn this study, the anammox process was applied for the first time to the treatment of ammonium-rich liquid residues produced by the two-stage anaerobic digestion of food waste (2sAD-FW); such residues may represent a significant environmental issue if not properly managed. A granular anammox reactor was fed with a progressively increasing share of partially nitritated 2sAD-FW wastewater. An alternative operating strategy based on partial by-pass of the partial nitritation unit was tested, in order to regulate the influent NO2/NH4 molar ratio without chemical addition. High nitrogen removal efficiency (89 ± 1%) and negligible nitrite discharge rates were achieved, together with high nitrogen removal rate / nitrogen loading rate (NRR/NLR, 97 ± 1%) and stable specific anammox activity (0.42 ± 0.03 gN2-N/gVSS·d). The observed NH4-removed/NO2-removed/NO3-produced molar ratio was in agreement with anammox stoichiometry, as confirmed by the low contribution (< 5%) of denitrification to nitrogen removal. Moreover, the possibility of using digital color characterization of granular biomass as a novel, simple tool for the monitoring of anammox biomass enrichment and process performance was investigated under dynamic conditions, using real wastewater: changes in granule color correlated well with the increasing share of 2sAD-FW wastewater in the influent (R2 = 83%), as well as with the decrease of anammox biomass abundance in the reactor (R2 = 68%). The results suggest that anammox may be successfully integrated into a 2sAD-FW system, thus enhancing its environmental sustainability
Preliminary evaluation of Sharon-Anammox process feasibility to treat Ammonium-rich effluents produced by double-stage anaerobic digestion of food waste
No full textIn this study, a Sharon-Anammox system was started up and fed with an ammonium-rich (1,500 mgNH4-N L−1) synthetic medium simulating the effluent produced by double-stage anaerobic digestion of food waste (AD-FW).
The effects of different process parameters (e.g., hydraulic retention time, nitrogen loading rate, etc.) and influent characteristics (e.g., influent alkalinity) on reactors performance were thoroughly evaluated. As to the Sharon reactor, reducing the hydraulic retention time did not cause any detrimental effect on overall process performance (the observed NH4-N removal efficiency and effluent NO2-N/NH4-N molar ratio were 60.8 ± 4.5% and 1.58 ± 0.27, respectively), although a slightly longer time was required to achieve process stability. The Anammox reactor was able to withstand the same nitrogen loading rates applied to the Sharon unit, and the observed nitrogen removal rate was high (89.9 ± 0.5%), indicating good process performance. The information gathered in this preliminary study will be useful for the treatment of real AD-FW wastewater
Autotrophic Nitrogen Removal From High Ammonium Containing Wastewater
Full text linkThe present thesis is framed within a wider project, promoted by the University of Cagliari and the Italian National Research Council, which pursued as its general objective the development of a novel integrated system for the biological combined anaerobic production of H2 and CH4 from the organic fraction of municipal solid waste (OFMSW), the valorization of solid residues by aerobic bio-oxidation (composting) and the biological treatment of ammonium-rich liquid by products by two-stage partial nitritation (PN)/anaerobic ammonium oxidation (anammox) process.
According to the project plan, a biological combined anaerobic production of H2 and CH4 from the OFMSW took place in two different bioreactors, in a double-step configuration. The effluent from the second reactor underwent a liquid/solid separation. The assessment of feasibility of the treatment of the liquid fraction by means of two-stage autotrophic nitrogen removal was the research question that tracked the main investigation line of the work described in the present thesis. The application of the coupled PN/anammox process, also referred to as fully autotrophic nitrogen removal, would allow to increase the sustainability of the entire OFMSW treatment chain, since the need for carbon addition (and concomitant increased sludge production) is omitted, oxygen consumption (i.e., energy requirement) is reduced, and the emission of nitrous oxide (a significant factor in the greenhouse gas footprint of the total water chain) can be cut significantly.
To date, few researches focused on the application of partial nitritation/anammox process for the treatment of the liquid fraction originated by the anaerobic digestion of organic substrates such as OFMSW. Moreover, the two-stage anaerobic digestion of such substrates is a relatively novel technology which has not deeply investigated yet in terms of its potential environmental impact, and few studies focused on characterization and management of the liquid residues.
To the best of our knowledge, no previous study was performed concerning the application of the two-stage PN/anammox process for the treatment of the anaerobic supernatant of a two-stage anaerobic digestion of organic fraction of municipal solid waste and food waste
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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