1,721,218 research outputs found
Application of a membrane biological reactor (MBR) for the removal of nutrients and micropollutants and wastewater reclamation and reuse
No full textL’acqua disponile per uso umano (diretto e non) sul nostro pianeta sta costantemente diminuendo, tanto che, secondo stime dell’ONU, nel 2025 due persone su tre non avranno accesso a risorse idriche utilizzabili. Ciò è imputabile non solo ai ridotti quantitativi disponibili, ma anche al costante peggioramento delle caratteristiche chimico-fisiche e microbiologiche delle riserve idriche. Ne consegue la necessità di introdurre processi avanzati per il trattamento delle acque reflue, in grado di produrre effluenti con qualità elevatissima, idonei tanto allo scarico in zone particolarmente sensibili dal punto di vista ambientale, quanto al diretto riutilizzo per fini industriali e/o agricoli. L’applicazione di processi biotecnologici è orami da tempo un must nel settore del trattamento delle acque reflue.
Nel corso del triennio di dottorato di ricerca si è quindi condotto lo studio approfondito di un processo biotecnologico per il trattamento avanzato di acque reflue reali di origine mista, civile ed industriale in bioreattore a membrana (MBR).The necessity to reclaim wastewater determined the introduction of memebrane bioreacotrs for successfull treatment at very high efficiecny standard
Some critical aspects of the enzymatic hydrolysis at high dry-matter content: a review
No full textEnzymatic hydrolysis represents the crucial phase in bioethanol production. Its aim is to convert pretreated lignocellulosic polymers in hexose sugars for fermentation into bioethanol. To be economically advantageous, the enzymatic hydrolysis should operate with a high concentration of dry matter. The drawback of this is the increase in the reaction medium’s viscosity and consequently bad mixing within the bioreactor due to the complexity of the lignocellulosic polymers. Another critical aspect of the enzymatic hydrolysis is enzyme deactivation, which is mainly due to two factors: the presence of lignin by-products, originating from the pretreatment of lignocellulosic biomass, and the accumulation of glucose in the reaction medium by cellulose hydrolysis. This review details these two critical aspects of enzymatic hydrolysis conducted with high dry-matter content. The most relevant milestones and technological solutions to improve rheological performance and to reduce enzyme deactivation have been investigated
Exploitation of Solar Energy for Ammonium Sulfate Recovery from Anaerobic Digestate of Different Origin
No full textDigestate represents the semi-liquid byproduct of the anaerobic digestion process. It was estimated that 56 Mtonnes of digestate are annually produced only in Europe. Digestate composition depends on the initial total solids (TS) mixture fed to the digester and by its origin (manure, food wastes, agricultural residues, wastewater sludge). Typical values for the different components include a stabilized organic matter content between 20 and 50 g/L, a good content of nitrogen compounds (2-8 g/kg) and of phosphorous compounds (up to 3 g/kg). In particular, ammonia presence in digestate is interesting for ammonium sulfate production, a fertilizer which favors plants' growth. Traditional ammonium sulfate synthesis is conducted by stripping followed by sulfuric acid absorption, a process which requires high energy and chemicals consumptions. This work investigates the exploitation of solar energy to evaporate the liquid phase of digestate in a lab-scale greenhouse. Digestate vapors, rich in ammonia, are sent in a Drechsler trap, filled with 38% w/w sulfuric acid solution, through three solar air fans. The process has been tested on digestates differing for TS content and origin. It emerged that the process is favored by digestates with high ammonia content, as those originated from manure, and a TS content of about 10% w/w, which allowed to obtain an ammonium sulfate concentration of about 2 M in the final solution
Beyond Anaerobic Digestion: New Perspectives for the Development of a Biorefinery Platform for the Simultaneous Production of Medium-Chain Fatty Acids by Chain Elongation and Biogas from Food Wastes
No full textThe medium chain fatty acids (MCFAs) obtained via chain elongation of short chain fatty acids are becoming a trend topic in the field of biorefinery research. Their synthesis can be implemented in the over 150 000 full-scale anaerobic digestion plants around the world, increasing the economic revenues derived from the mere biogas production. This paper offers a critical insight into the needed actions for the creation of biorefinery model for the simultaneous production of the MCFAs and biogas from the organic fraction of municipal solids wastes and the most abundant food wastes, such as brewery wastes, grape pomace, and cheese whey. A three-stage chain elongation process was suggested with the aim to optimize the operational parameters and the pretreatments for the production and purification of all the compounds involved in the process: (i) the electron donor, (ii) the electron acceptor compounds, and (iii) their reaction into a separate reactor for the synthesis of MCFAs. The remaining organic matter from the fermentation steps for the electron donor and the electron acceptor molecules can be sent to the already-existing AD plant for biogas production. Specifically, it was emphasized that the molar ratio between the electron donor (ethanol or lactate) and electron acceptor compounds (volatile fatty acids, VFAs) in the ranges of 3:1 and 6:1 can optimize the MCFAs yield. Regarding the reactor configuration, batch mode was not able to ensure high yield, while the continuous mode operating at hydraulic retention time (HRT) of 5-10 days and at neutral or slightly acidic pH led to high conversion of food wastes in MCFAs (25-50% (w/w)). Nanofiltration and pertraction were the best techniques to recover the MCFAs from the other organic compounds, with very high yields in the range of 75%-95%. The applications for MCFAs involved different fields: from the production of jet and diesel fuels to polyhydroxyoctanoate and polyhydroxydecanoate biosynthesis. Finally, the main challenges for a full-scale implementation of the chain elongation process were discussed and emphasized: among them, the low concentration of the MCFAs in the reaction medium and the need to increase the technology readiness level of the recovery and purification techniques were considered to be priorities
Carbon footprint of aerobic biological treatmentof winery wastewater
No full textThe carbon associated with wastewater and its treatment accounts for approximately 6% of the
global carbon balance. Within the wastewater treatment industry, winery wastewater has a minor
contribution, although it can have a major impact on wine-producing regions. Typically, winery
wastewater is treated by biological processes, such as the activated sludge process. Biomass
produced during treatment is usually disposed of directly, i.e. without digestion or other
anaerobic processes. We applied our previously published model for carbon-footprint calculation
to the areas worldwide producing yearly more than 106 m3 of wine (i.e., France, Italy, Spain,
California, Argentina, Australia, China, and South Africa). Datasets on wine production from the
Food and Agriculture Organisation were processed and wastewater flow rates calculated with
assumptions based on our previous experience. Results show that the wine production, hence
the calculated wastewater flow, is reported as fairly constant in the period 2005 – 2007.
Nevertheless, treatment process efficiency and energy-conservation may play a significant role on
the overall carbon-footprint. We performed a sensitivity analysis on the efficiency of the aeration
process (aSOTE per unit depth, or aSOTE/Z) in the biological treatment operations and showed
significant margin for improvement. Our results show that the carbon-footprint reduction via
aeration efficiency improvement is in the range of 8.1 to 12.3%
Full scale experiences of anaerobic digestion of the organic fraction of municipal solid waste in Italy - from collection to energy and valuable products
No full textConfronto tra la digestione anaerobica termofila e mesofila: produzione di biogas, produzione di energia, efficienza di degradazione
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