1,721,018 research outputs found
Produzione di Poliidrossialcanoati (PHA) dal trattamento dei fanghi e delle acque di scarico municipali
No full textL’ approccio proposto in questo lavoro, nel programma del progetto europeo ROUTES FP7, è mirato a collocare la produzione di polimeri biodegradabili (poliidrossialcanoati, PHA) nell’ambito del trattamento delle acque di scarico municipali e della minimizzazione dei fanghi prodotti nel processo stesso. Diversamente dallo schema di processo di produzione di PHA ampiamente studiato, in cui i reflui fermentati ricchi in VFA venivano utilizzati sia per la selezione del consorzio microbico misto (attraverso cicli feast-famine), che per la successiva fase di produzione di PHA (accumulo intracellulare), in questo processo innovativo, lo step di selezione viene eseguito utilizzando reflui urbani non fermentati in un processo a fanghi attivi creato ad-hoc. I reflui ricchi in VFA, provenienti dalla fermentazione acidogenica di fanghi primari, vengono invece utilizzati unicamente nello stadio di accumulo, evitandone lo spreco nella fase di selezione. Questo tipo di processo produttivo offre dunque la possibilità di trattamento delle acque reflue municipali e di rimozione del carbonio, simultaneamente alla produzione di un
consorzio microbico misto abile a produrre PHA. Inoltre, il fango primario può essere fortemente ridotto, convertendone i solidi organici in VFA attraverso la fermentazione acidogenica; il fango secondario, con una migliorata capacità di stoccaggio di PHA, può essere completamente convogliato dalla fase di selezione alla fase di accumulo, recuperando parte di esso come PHA, prodotto finale ad alto valore aggiunto.
Il processo complessivo è stato valutato sia in scala di laboratorio che in scala pilota, utilizzando acque di scarico municipali (sintetiche e reali) per lo stadio di selezione; e substrati ad alto contenuto in VFA (fanghi primari fermentati, fanghi primari sottoposti a processi di wet-oxidation, fanghi primari miscelati con la frazione organica dei rifiuti solidi municipali) per la fase di accumulo. I risultati hanno dimostrato la fattibilità dell’approccio innovativo proposto, con rendimenti finali di stoccaggio e contenuto intracellulare di PHA fino a 0.38 COD/COD e 34% (w/w) rispettivamente
Carbon recovery from wastewater through bioconversion into biodegradable polymers
Full text linkPolyhydroxyalkanoates (PHA) are biodegradable polyesters that can be produced in bioprocesses from renewable resources in contrast to fossil-based bio-recalcitrant polymers. Research efforts have been directed towards establishing technical feasibility in the use of mixed microbial cultures (MMC) for PHA production using residuals as feedstock, mainly consisting of industrial process effluent waters and wastewaters. In this context, PHA production can be integrated with waste and wastewater biological treatment, with concurrent benefits of resource recovery and sludge minimization. Over the past 15 years, much of the research on MMC PHA production has been performed at laboratory scale in three process elements as follows: (1) acidogenic fermentation to obtain a volatile fatty acid (VFA)-rich stream, (2) a dedicated biomass production yielding MMCs enriched with PHA-storing potential, and (3) a PHA accumulation step where (1) and (2) outputs are combined in a final biopolymer production bioprocess. This paper reviews the recent developments on MMC PHA production from synthetic and real wastewaters. The goals of the critical review are: a) to highlight the progress of the three-steps in MMC PHA production, and as well to recommend room for improvements, and b) to explore the ideas and developments of integration of PHA production within existing infrastructure of municipal and industrial wastewaters treatment. There has been much technical advancement of ideas and results in the MMC PHA rich biomass production. However, clear demonstration of production and recovery of the polymers within a context of product quality over an extended period of time, within an up-scalable commercially viable context of regional material supply, and with well-defined quality demands for specific intent of material use, is a hill that still needs to be climbed in order to truly spur on innovations for this field of research and development. © 2016 Elsevier B.V
Feast-famine selection of microbial mixed-cultures for PHA production based on carbon removal from municipal wastewater without previous fermentation
No full textPolyhydroxyalkanoates (PHA) have attracted interest since they are biodegradable polyesters with comparable properties to petroleum-based polyolefins. The PHA production by mixed microbial cultures (MMC) has been largely investigated in sequencing batch reactors (SBRs) under dynamic feeding conditions (feast-famine, FF). Streams rich in volatile fatty acids (VFAs), obtained from the acidogenic fermentation of wastewaters, have been used for MMC selection in SBR, and for
subsequent PHA accumulation/production with the pre-selected MMC.
In the proposed novel approach, the MMC selection is achieved in SBR treating municipal notfermented wastewater, and PHA accumulation/production is conducted with VFA-rich streams in subsequent step. The MMC selection was conducted at pilot-scale with real wastewater and confirmed at lab-scale with a synthetic one. The storage capacity of the selected MMCs was evaluated in batch accumulation tests using synthetic VFAs stream.
In both SBRs, the feasibility of selecting a MMC with enhanced PHA storage capacity was demonstrated and a stable FF regime was established, as evidenced by respirometric profiles. In the lab-scale SBR, the treatment efficiency of the influent soluble COD (SCOD) was more than 90%, whereas in the pilot-scale, around 70-80%. In batch tests, the lab-scale biomass achieved up to 20% (gPHA/gVSS) PHA content whereas the pilot-scale biomass achieved up to 34% (gPHA/gVSS),
even if the initial storage kinetics was lower than the lab-scale biomass. Differences in performance between SBRs are possibly derived from differences in feed characteristics and operating conditions.
Both SBRs demonstrated the possibility to combine PHA production with municipal wastewater treatment. This approach opens the possibility to profit from the C content of municipal wastewaters for MMC selection without the need to utilize fermented VFA-rich feedstocks, which can then be fully utilized for PHA accumulation/production
Method for increased productivity of polyhydroxyalkanoates (phas) in fed-batch processes for biomass derived from the treatment of wastewater
No full textThis disclosure relates to methods for producing a PHA-rich-biomass from open mixed cultures. Mixed liquor containing biomass is directed into a fed-batch reactor. The reactor includes at least one biomass stimulating zone and at least one biomass maintenance zone. A feed containing RBCOD, bioavailable N, and bioavailable P is directed into the fed-batch reactor. The respiration rate of at least a portion of the biomass is intermittently and repeatedly stimulated in the stimulating zone by directing the feed into the fed-batch reactor and exposing the biomass to a relatively high concentration of RBCOD. The biomass is then transferred to the maintenance zone, where the biomass is exposed to a relatively low concentration of RBCOD. Thereafter, the biomass is circulated back and forth between the stimulating zone and the maintenance zone. Throughout the methods, the concentration of N and/or P relative to the RBCOD in the feed is controlled by controlling the ratio of N to RBCOD and/or the ration of P to RBCOD in the feed
Process for enhancing polyhydroxyalkanoate accumulation in activated sludge biomass
No full textA process for producing PHA comprises obtaining biomass produced in the course of biologically treating a first wastewater source containing RBCOD. The biomass is to be exploited with a second wastewater source having a different RBCOD content from the first wastewater source in order to accumulate and thereby produce PHA. Before subjecting the biomass to a PHA accumulation process, the biomass PHA accumulation potential is enhanced via an acclimation process with the second wastewater source. During acclimation, the biomass is subjected to repeated feast-famine periods. During each feast period, the biomass is exposed to a fraction of the second wastewater source. The RBCOD uptake and/or biomass respiration rate is directly or indirectly measured during each feast period. The famine period is maintained for a period of time that is at least two times greater than the length of time of the proceeding feast period. After at least two feast-famine acclimation periods or after one or more measured parameters reveal an increased RBCOD relative uptake or respiration rate of the biomass during a subsequent feast period, the biomass is subjected to a PHA accumulation process using the second wastewater source
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
Polyhydroxyalkanoate (PHA) storage within a mixed-culture biomass with simultaneous growth as a function of accumulation substrate nitrogen and phosphorus levels
No full textThe response of a mixed-microbial-culture (MMC) biomass for PHA accumulation was evaluated over a range of relative nitrogen (N) and phosphorus (P) availabilities with respect to the supply of either complex (fermented whey permeate - FWP) or simpler (acetic acid) organic feedstocks. Fed-batch feed-on-demand PHA accumulation experiments were conducted where the feed N/COD and P/COD ratios were varied ranging from conditions of nutrient starvation to excess. A feast-famine enrichment (activated sludge) biomass, produced in a pilot-scale aerobic sequencing batch reactor on FWP and with a long history of stable PHA accumulation performance, was used for all the experiments as reference material. FWP with N/COD ratios of (2, 5, 15, 70mg/g all with P/COD=8mg/g) as well as simulated FWP with nutrient starvation (N/COD = P/COD=0) conditions were applied. For the acetic acid accumulations, nutrient starvation as well as N/COD variations (2.5, 5, 50mg/g all with P/COD=9mg/g) and P/COD variations (0.5, 2, 9, 15mg/g all with N/COD=10mg/g) were evaluated. An optimal range of combined N and P limitation with N/COD from 2 to 15mg/g and P/COD from 0.5 to 3mg/g was considered to offer consistent improvement of productivity over the case of nutrient starvation. Productivity increased due to active biomass growth of the PHA storing biomass without observed risk for a growth response overtaking PHA storage activity. PHA production with respect to the initial active biomass was significantly higher even in cases of excess nutrient additions when compared to the cases of nutrient starvation. The 24-hPHA productivities were enhanced as much as 4-fold from a base value of 1.35g-PHA per gram initial active biomass with respect nutrient starvation feedstock. With or without nutrient loading the biomass consistently accumulated similar and significant PHA (nominally 60% g-PHA/g-VSS). Based on results from replicate experiments some variability in the extant biomass maximum PHA content was attributed to interpreted differences in the biomass initial physiological state and not due to changes in feedstock nutrient loading. We found that the accumulation process production rates for mixed cultures can be sustained long after the maximum PHA content of the biomass was reached. Within the specific context of the applied fed-batch feed-on-demand methods, active biomass growth was interpreted to have been largely restricted to the PHA-storing phenotypic fraction of the biomass. This study suggests practical prospects for mixed culture PHA production using a wide range of volatile fatty acid (VFA) rich feedstocks. Such VFA sources derived from residual industrial or municipal organic wastes often naturally contain associated nutrients ranging in levels from limitation to excess
Acclimation process for enhancing polyhydroxyalkanoate accumulation in Aactivated-sludge biomass
No full textA strategy was evaluated for conditioning activated sludge biomass to a new substrate whereby the polyhydroxyalkanoate (PHA) accumulation capacity of the biomass was enhanced based on a series of aerobic feast– famine acclimation cycles applied prior to PHA accumula- tion. Different biomass types enriched during the treatment of municipal wastewater at laboratory, pilot, and full scales were exposed to aerobic feast–famine acclimation cycles at different feast-to-famine ratios with an acetate–propi- onate mixture (laboratory scale), acetate (pilot scale), and fermented waste–sludge centrate (pilot scale). A sevenfold increase in specific PHA storage rates and 20% increase in substrate utilization rates were observed during acclimation cycles (laboratory acetate–propionate). Biomass acclimation led to more than doubling of the specific substrate utiliza- tion rates, PHA storage rates, biomass PHA contents, and specific PHA productivities (per initial biomass) during PHA accumulation. The biomass PHA contents were found to increase due to acclimation from 0.19 to 0.34 (laboratory acetate–propionate), 0.39 to 0.46 (pilot acetate) and 0.19 to 0.25 gPHA/gVSS (pilot centrate). A similar bacterial com- munity structure during acclimation indicated that a physi- ological rather than a genotypic adaptation occurred in the biomass. The physiological state of the biomass at the start of PHA accumulation was deemed significant in the subse- quent PHA-accumulation performance. Positive acclimation trends can be monitored by measuring the relative increase in feast substrate utilization or respiration rates with respect to those of the first acclimation cycle
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
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