1,721,004 research outputs found
PHA pilot plant pictures deliverable 3.3
No full textThe dataset includes the pictures of the pilot plant platform for PHA production reported in the deliverable 3.3, the pictures are related to the description of the two experimental periods of the pilot plant platform. The pictures described the pilot plant platform during the first experimental period in which the feasibility of the process and the future perspectives in terms of scalability were determined and the second experimental period, dedicated to the optimization of the pilot plant so to achieve better yields in its different steps. The pictures highlight the change of many components such as pipes/pumps and valves, during the second period of the experimental activity to optimize the pilot plant efficiency
Microbial electrolysis cell to enhance energy recovery from wastewater treatment
No full textEnergy intensive activate sludge treatment is the most utilized technology for municipal wastewater treatment.
However, an innovative way to harvest part of the energy contained in municipal wastewater is offered by the
utilization of microbial electrolysis cells (MECs). In an MEC, through the utilization of electro active
microorganism, is possible to couple the oxidation organic matter with the generation of value-added reduced
products, such as methane, similar to the anaerobic digestion process. MECs typically consist of a bio-anode
and a (bio)-cathode separated by an ion exchange membrane (IEM). The addition of external energy usually
is required to make the cathodic reaction thermodynamically feasible. Here, a continuous flow methane-
producing MEC equipped with an anion exchange membrane was operated in a continuous flow mode for
over 60 d at two different poised anode potentials (+ 0.20 and -0.10 V vs. standard hydrogen electrode, SHE)
and with a fixed organic load rate (1.08 gCOD/Ld). The MEC showed a high COD removal efficiency (92 ±
1%), with a net energy recovery (122 ± 3 %, at -0.1 V) and low sludge production (0.09 gCOD/gCOD), making
its utilization attractive in the frame of low strength wastewater treatment
Celle di elettrolisi microbiche per la il recupero energetico e la depurazione di acque reflue civili
No full textL’attività antropica sul territorio si riflette in un eccesso di immissione di sostanze organiche, azoto e fosforo che possono provocare effetti di eutrofizzazione delle acque superficiali con conseguente impatto sulla flora e la fauna acquatica nonché sulla possibile di sviluppo di patogeni. La necessità di restituire ai bacini idrici acque depurate che non impattino sull’ecosistema è di centrale importanza per la conservazione del territorio e per la sicurezza della salute. Negli ultimi decenni il collettamento dei reflui civili ed industriali è aumentato significativamente, tuttavia, in Italia il 3.2 % di abitanti sono collegati a fognature che si riversano nei bacini idrici senza subire alcun trattamento, mentre lo 0.6% della popolazione è priva di rete fognaria pubblica1. Per inefficienza depurativa sancita dall’Unione Europea con la sentenza di condanna della Corte di Giustizia Europea l’Italia è stata sanzionata nel 20112. Nel campo della depurazione, soprattutto per i reflui civili, solitamente a basso carico organico, il processo di depurazione più diffuso è il processo a fanghi attivati, il quale richiede considerevoli costi di investimento e di funzionamento (areazione) nonché di smaltimento dei sottoprodotti di processo (fanghi di supero). Per ridurre il volume di fanghi di supero si è ricorso negli anni al processo di digestione anaerobica che permette la trasformazione della sostanza organica particolata in una miscela gassosa denominata biogas che consiste principalmente in una miscela di anidride carbonica e metano. La digestione anaerobica è un processo che permette un recupero netto di energia da matrici organiche di scarto, tuttavia il suo impiego è limitato al trattamento di matrici ad elevato contenuto di sostanza organica. Un processo innovativo per il recupero energetico da acque di scarico a basso carico organico può essere offerto dal processo di bioelettrometanogenesi mediante l’utilizzo di una cella di elettrolisi microbica (MEC). Mediante l’utilizzo di microrganismi elettroattivi è possibile accoppiare l’ossidazione della sostanza organica alla generazione di un prodotto catodico di interesse quali l’idrogeno, il metano o l’acetato. Mediante l’utilizzo di colture chemoautotrofe quali catalizzatori biologici nel comparto catodico della MEC, è possibile quindi indirizzare la riduzione della CO2 verso il metano. Per accoppiare le reazioni di ossidazione e riduzione tuttavia è necessario applicare un potenziale elettrico esterno per superare le barriere termodinamiche e cinetiche; nell’ottica di fornire energia elettrica proveniente da fonti energetiche rinnovabili, le MEC potrebbero costituire una tecnologia sostenibile per il trattamento di reflui civili ad elevata versatilità, utilizzabile in aeree non servite da reti fognarie o da impianti per il trattamento di reflui. Nella presente ricerca vengono presentati i risultati ottenuti alimentando il comparto anodico di una MEC in scala laboratorio finalizzata alla produzione di metano, con differenti substrati organici sia sintetici (acetato3, peptone, estratto di lievito, glucosio4), sia reali (digestato anaerobico e fermentato acido). La valutazione delle performance delle reazioni sono state valutate mediante il bilancio dell’elettrone (efficienza coulombica ed efficienza di cattura catodica) mentre l’efficienza di rimozione della sostanza organica da parte del reattore mediante il bilancio di materia; infine particolare enfasi è stata data all’utilizzo del bilancio di energia con il fine di valutare il parametro efficienza energetica dell’intero processo
Role of C/N ratio in a pilot scale Microbial Electrolysis Cell (MEC) for biomethane production and biogas upgrading
No full textMicrobial electrolysis cells (MECs) permit to couple the oxidation of waste organic streams (e.g., wastewater, fermentate or digestate) with the reduction of carbon dioxide into products with a high market value (e.g., methane or acetic acid). MECs exploit the ability of electroactive microorganisms to use a solid electrode as final electron acceptor or donor. Here, a micro pilot tubular MEC has been set up combining the anodic oxidation of the organic matter with the bioelectromethanogenesis reaction in the cathodic chamber. Seven different synthetic feeding solutions, simulating a domestic wastewater or an acidogenic fermentate, have been used to test different C/N ratio on the performance of the MEC bioanode in the range between 25 and 0.4 (molC/molN). As a main result it was found that, under the same operating conditions (i.e., anode potential controlled at + 0.2 V vs SHE and HRT of 0.5 d), a high C/N ratio (e.g., 19 mol/mol) promotes the bioelectrochemical metabolism of the electroactive biofilm. These findings are relevant for a practical application of the technology considering the variable content of carbon and nitrogen in real feedstocks
Three-chamber microbial electrolysis cell as a post-treatment step to refine both biogas and liquid effluent from anaerobic digestion
No full textPresent research is focused on the performance of a fully biocatalyzed three-chamber microbial electrolysis cell in the perspective of a self sustainable post-treatment process to enhance both digestate and biogas quality from the anaerobic digestion (AD). The rationale of this study was to couple carbon oxidation and ammonia removal in the anodic compartment to carbon dioxide removal and additional methane formation in the cathode compartment. To accomplish this objectives a bench-scale three-chamber continuous-flow MEC was developed, where a biomass-free accumulation chamber was inserted between anodic and cathodic compartments and separated by either protonic or anionic exchange membrane, respectively. The expected role of the intermediate chamber was to receive both ammonium and bicarbonate ions from the anodic and cathodic compartments respectively.
The MEC was continuously operated in a potentiostatic mode with the typical three electrode configuration, after having inoculated the anodic and cathodic compartments by an activated sludge and an anaerobic sludge, respectively. The anode was operated under continuous flow feeding of organic carbon while the cathode was operated in batch condition, but for a 70/30 % N2/CO2 gas mixture (simulating typical methane/CO2 ration in the biogas) was continuously bubbled inside the chamber, to ensure both pH control and inorganic carbon supply for methanogens. The MEC performance was assessed through COD and electron balance as well as through removal efficiency of ammonia and carbon dioxide
Electro-fermentation and redox mediators enhance glucose conversion into butyric acid with mixed microbial cultures
Full text linkElectro-fermentation (EF) is an emerging and promising technology consisting in the use of a polarized electrode to control the spectrum of products deriving from anaerobic bioprocesses. Here, the effect of electrode polarization on the fermentation of glucose has been studied with two mixed microbial cultures, both in the absence and in the presence of exogenous redox mediators, to verify the viability of the proposed approach under a broader and previously unexplored range of operating conditions. In unmediated experiments, EF (with the cathode polarized at −700 mV vs. SHE, Standard Hydrogen Electrode) caused an increase in the yield of butyric acid production provided that glucose was consumed along with its own fermentation products (i.e. acetic acid and ethanol). The maximum obtained yield accounted for 0.60 mol mol−1. Mediated experiments were performed with Neutral Red or AQDS at a concentration of 500 μM both in the absence and in the presence of the electrode polarized at −700 mV or −300 mV vs. SHE, respectively. Mediators showed a high selectivity towards the generation of n-butyric acid isomer from the condensation of acetate and ethanol, hence suggesting that they provided microbial cells with the required reducing power otherwise deriving from glucose in unmediated experiments
Influence of the set anode potential on the performance and internal energy losses of a methane-producing microbial electrolysis cell
No full textThe effect of the set anode potential (between +200 mV and −200 mV vs. SHE, standard hydrogen electrode) on the performance and distribution of internal potential losses has been analyzed in a continuous-flow methaneproducing microbial electrolysis cell (MEC). Both acetate removal rate (at the anode) and methane generation rate (at the cathode) were higher (1 gCOD/L day and 0.30 m3 /m3 day, respectively) when the anode potential was controlled at +200 mV. However, both the yields of acetate conversion into current and current conversion into methane were very high (72–90%) under all the tested conditions. Moreover, the sum of internal potential losses decreased from 1.46 V to 0.69 V as the anode potential was decreased from +200 mV to −200 mV, with cathode overpotentials always representing the main potential losses. This was likely to be due to the high energy barrier which has to be overcome in order to activate the cathode reaction. Finally, the energy efficiency correspondingly increased reaching 120% when the anode was controlled at −200 mV
Two phase anaerobic digestion effluents as feedstocks to bioelectromethanogenesis sustenance
No full textIn a microbial electrolysis cell (MEC), it is possible to conduct the two main reactions of anaerobic digestion (AD) in two physically separated chambers, by coupling COD oxidation into CO2 (in the bio-anode) to the CO2 removal and reduction into methane (in the bio-cathode), thanks to the transfer of reducing power by the electrical and ionic current. Moreover, AD and MEC can be integrated, by using the MEC to upgrade methane content of the AD biogas while also using residual COD from AD anaerobic digestate, so improving the overall energy efficiency and the quality of the products of conventional AD (Villano et al 2013). However, this approach has not been tested with real substrates yet and concerns also exist on possible fouling and poisoning effects on ionic membrane and/or electrodic material.
Here, a continuous-flow 2-chamber MEC was operated under anodic potentiostatic control (at 0.2 vs SHE), to compare its performance by feeding the bio-anode with synthetic vs real substrates; both an anaerobic digestate (from methanogenic stage) and an acidogenic fermentate (from preliminary acidogenic stage) were tested and compared with a synthetic substrate mixture (as described in Zeppilli et al 2014). The MEC was equipped with a proton exchange membrane (PEM) and both electrodic beds made by graphite granules. The cathode chamber was fed by a continuous sparging of a gas mixture of N2/CO2 (70/30 v/v to simulate biogas), whereas a concentrated liquid stream was spilled to counterbalance osmotic water flow across PEM.
The MEC performed poorly (23 ± 4 mA) when fed by the anaerobic digestate because its residual COD resulted to be poorly available for anodic oxidation, whereas the mixture of both first and second stage AD effluents gave slightly better performance than the synthetic mixture(60 ± 4 mA vs 50 ± 1 mA, respectively). The latter evidence was not only due to high VFA-content but also to high ammonia concentration. Being ammonia higher than in the synthetic mixture, the percentage of ionic current transported across the PEM by the ammonium instead of the proton was increased from 2 to 20 %. This eventually increased the net generation of the alkalinity in the cathodic chamber and thus bicarbonate concentration in the cathodic spill. Overall, by using the VFA-rich and ammonia-rich mixture of both real effluents, a nitrogen removal rate of 228 mg/Ld was obtained while an average CO2 removal of 3.4 g/Ld was observed in the cathode.
Fouling phenomena were observed to decrease the MEC performance, likely due to the high content of suspended solids in both real substrates (in spite of preliminary filtration at around 0.2 mm cut off). However, adverse fouling effects were easily recovered by periodic backwashing of the bio-anode
Metagenomic analysis reveals microbial interactions at the biocathode of a bioelectrochemical system capable of simultaneous trichloroethylene and cr(vi) reduction
Full text linkBioelectrochemical systems (BES) are attractive and versatile options for the bioremediation of organic or inorganic pollutants, including trichloroethylene (TCE) and Cr(VI), often found as co-contaminants in the environment. The elucidation of the microbial players’ role in the bioelectroremediation processes for treating multicontaminated groundwater is still a research need that attracts scientific interest. In this study, 16S rRNA gene amplicon sequencing and whole shotgun metagenomics revealed the leading microbial players and the primary metabolic interactions occurring in the biofilm growing at the biocathode where TCE reductive dechlorination (RD), hydrogenotrophic methanogenesis, and Cr(VI) reduction occurred. The presence of Cr(VI) did not negatively affect the TCE degradation, as evidenced by the RD rates estimated during the reactor operation with TCE (111±2 μeq/Ld) and TCE/Cr(VI) (146±2 μeq/Ld). Accordingly, Dehalococcoides mccartyi, the primary biomarker of the RD process, was found on the biocathode treating both TCE (7.82E+04±2.9E+04 16S rRNA gene copies g−1 graphite) and TCE/Cr(VI) (3.2E+07±2.37E+0716S rRNA gene copies g−1 graphite) contamination. The metagenomic analysis revealed a selected microbial consortium on the TCE/Cr(VI) biocathode. D. mccartyi was the sole dechlorinating microbe with H2 uptake as the only electron supply mechanism, suggesting that electroactivity is not a property of this microorganism. Methanobrevibacter arboriphilus and Methanobacterium formicicum also colonized the biocathode as H2 consumers for the CH4 production and cofactor suppliers for D. mccartyi cobalamin biosynthesis. Interestingly, M. formicicum also harbors gene complexes involved in the Cr(VI) reduction through extracellular and intracellular mechanisms
Role of the Electroactive and Non-electroactive Surface Area (EASA and nEASA) for Electroactive Biofilms in Bioelectrochemical Systems
Full text linkThe role of the electroactive surface area (EASA) and of the non-electroactive surface area (nEASA) was studied to better understand electroactive biofilm’s (EAB) growth and performance in four different systems. Those systems consisted in four 1L glass bottles filled with mineral medium and substrates, a stainless-steel cathode and a bioanode. Four different types of bioanode were assembled in order to study the EASA and nEASA role. A potentiostat controlled the anodic potential, which was fixed in every system at + 0.2 V vs SHE (standard hydrogen electrode). To measure the EASA of every system, cyclic voltammetries (CVs) were carried out at different scan rates. Comparing them with the one obtained with a reference system, each EASA is easily calculated. The nEASA, instead, was measured calculating the geometric volume. The obtained results demonstrate the fundamental role of the EASA and, moreover, the necessity to reduce as much as possible the nEASA in order to enhance the performance
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