1,720,989 research outputs found
Energy and material recovery from high-loaded organic substrates: A territory-oriented approach
Full text linkThis Ph.D. research was aimed at liquid organic substrates valorisation, by means of energy and material recovery. The mountain area of Friuli-Venezia Giulia region was selected as case-study: Cheese Whey (CW), condensate Pulp and Paper (P&P) WW, OFMSW, brewery waste (spent grain, yeast, whirlpool residue, end-of-fermentation beer) and slaughterhouse waste were selected for AD process application, as well as for resource recovery. The work started with a literature study, followed by physicochemical characterization, BMP tests, continuous UASB tests, and it was then completed with an energetic analysis, as well as with some final remarks and suggestions. The Ph.D. thesis starts with a general introduction, aimed at describing EU perspective in renewable energy and waste management. Given the increasing importance of biomethane, the currently applied technologies for biogas upgrading are briefly discussed, as well. Then, UASB anaerobic treatment, as an interesting process for energy recovery from industrial wastewater, and Tolmezzo WWTP (143,000 PE) are described. Successively, the analysed substrates are introduced, and the obtained results are presented. The results from BMP tests follow: these data were useful to estimate potential methane yields and maximum methane fluxes, as well as to introduce continuous UASB tests, that were conducted on a pilot-UASB unit. In the final chapter, some energetic and material recovery considerations are drawn, considering the actual energetic costs in selected real plants and suggesting, for each substrate, an optimization route. The results underlined that a high potential is present for biogas production in dairies: CW can be successfully digested, and, if performed at plant level, AD process can provide most of the electricity and heat needed by the process. The installation of simple digesters can allow to reduce pay-back time. In larger dairies, instead, resource recovery should be privileged, due to the extra income that could be provided by the obtained products. Ultrasound (US) pre-treatment was shown to be effective in increasing biogas yields, but only at low applied US energy. OFMSW can be separated into a liquid fraction, highly biodegradable and having good methane potential, and a solid fraction, easily stabilized through composting. Given the general low amount of available organic waste in the analysed territory, co-digestion of OFMSW liquid fraction with other substrates, such as excess sewage sludge, can be an interesting option, to increase biogas yields and obtain a co-digestion mixture having optimum characteristics. Condensate water is a highly concentrated P&P WW, and is amenable to be pre-treated using UASB technology; this can reduce organic load to the aerobic basins, leading to a significant energy saving for aeration. Brewery organic waste is characterized by a pool of different substrates, including spent grain (trub), yeast, whirlpool residue and end-of-fermentation beer. A good potential for biogas production was shown to be present mainly in spent grain and yeast. The addition of little amounts of biochar and granular activated carbon increased obtainable methane yields in a significant way (more than 35%), so a synergistic effect between biomass plants and processing plants can be achieved, improving energy production. Co-digestion of brewery organic substrates at plant level can be successfully performed. Given the high energy demand of this plants, AD process appears to be a good solution to reduce operating costs. Slaughterhouse waste, finally, is a harsh substrate, difficult to hydrolyse, and rich of proteins and fats: in order to be successfully treated using AD process, efficient pre-treatments should be investigated. Moreover, sanitary protocols must be followed, for its proper management. It could be interesting to evaluate the effects of co-digestion with complementary substrates, rich in C
UASB anaerobic treatment and OFMSW reutilization: Tolmezzo case potentiality; Tratament anaerobic UASB e riûs da FORSU: potenzialitât dal cas di Tumieç
No full textMore and more interest is being dedicated to anaerobic processes in the scientific
literature; in particular, high velocity reactors, such as the Up-flow Anaerobic
Sludge Blanket reactor, are able to reduce the required HRT and to optimize biogas
production. This kind of reactors is particularly indicated for high concentrated wastewaters,
in which the soluble fraction is prevalent over the suspended one. In this cases,
the anaerobic process can achieve high efficiencies, in terms of COD removal, with low
energy requirements, if compared to a traditional activated sludge process. This work is
focused on Tolmezzo wastewater treatment plant, because it contains a UASB reactor,
that is inactive since 2007, and so it is, potentially, a source of clean energy. It is supposed
to feed the reactor with the liquid fraction of Organic Fraction of Municipal Solid
Waste (OFMSW), separately segregated in the local geographic area, while the solid
fraction, residual from the separation process, is suitable to be sent to a composting
plant
Lifting craft breweries sustainability through spent grain valorisation and renewable energy integration: A critical review in the circular economy framework
Full text linkDue to the constantly growing customers’ demand for local products, a significant rise in craft breweries' number, as well as in craft beer production, has been observed in the last years. The sustainability of craft breweries is a hot scientific topic, which involves water and waste management, energy efficiency, and renewable energy implementation. Life cycle assessment (LCA) and life cycle costing (LCC) are useful tools to compare alternative waste management pathways in a standardised manner, highlighting the hotspots with the highest environmental/economic impact.
Brewery-spent grain (BSG) represents the main organic by-product of beer production; traditionally, it has been used as animal feed. However, not always there are enough farms to utilise all the produced BSG locally, especially in developed countries and industrialised areas, so alternative solutions should be exploited. This review gives a thorough overview of the different technological pathways for BSG valorisation considering the state-of-the-art of research on the topic, including both traditional (animal feed, composting, anaerobic digestion) and innovative (thermochemical processes, pellets production, food production, chemicals' extraction) solutions. The applicability of each technology to craft breweries is specifically discussed. To enhance craft breweries’ sustainability and decarbonise industrial processes, renewable energy generation is considered as well either through photovoltaic (PV) or solar thermal: while solar thermal implementation appears cumbersome due to the batch nature of the processes, PV installation is a mature, simple and straightforward solution. Geothermal energy integration is mentioned as well. Finally, a lack of studies on LCA/LCC application to compare the presented alternative BSG management pathways is highlighted, requiring intensive future research
Tackling climate change through wastewater reuse in agriculture: A prioritization methodology
Full text linkWater shortages, exacerbated by climate change, are posing a major global challenge, particularly impacting the agricultural sector. A growing interest is raised towards reclaimed wastewater (RWW) as an alternative irrigation source, capable of exploiting also the nutrient content through the fertigation practice. However, a prioritization methodology for selecting the most appropriate wastewater treatment plants (WWTPs) for implementing direct RWW reuse is currently missing. Such prioritization would benefit water utilities, often managing several WWTPs, and policymakers in optimizing economic asset allocation. In this work, a prioritization framework is proposed to evaluate WWTPs' suitability for implementing direct RWW reuse considering both WWTP and surrounding territory characteristics. This procedure consists of four key steps. Firstly, a techno-economic model was developed, in which monthly mass balances on water and nutrients are solved by matching crop requirements, rainfall conditions, and effluent characteristics. Economic suitability was quantified considering economic benefits due to savings in freshwater resource, mineral fertilizers and avoided greenhouse gases emissions, but also losses in crop yield due to RWW salinity content. Secondly, a classification procedure was coded to select representative WWTPs among a set of WWTPs, based on their size, presence of nutrient removal processes, and type of crops in their surroundings. The techno-economic model was then applied to these selected WWTPs. Thirdly, input parameters' relevance in determining WWTP suitability for RWW reuse was ranked. Finally, scenario analyses were conducted to study the influence of rainfall patterns and nutrient treatment removal on the RWW reuse feasibility. The type of crops surrounding the WWTPs and RWW salinity content resulted to be crucial elements in determining WWTPs suitability for RWW reuse implementation. The proposed methodology proved to be an effective support tool for policymakers and water utilities to assess the techno-economic feasibility of direct RWW reuse, generalizing results to several combinations of WWTPs and crops
Corrigendum to “100% renewable wastewater treatment plants: Techno-economic assessment using a modelling and optimization approach” [Energy Convers. Manage. 239 (2021) 114214]
No full textEnvironmental methane emissions from seagrass wrack and evaluation of salinity effect on microbial community composition
No full textMethane generation from seagrass contributes to green-house gases emissions but can also be a potential controlled biogas source. Understanding the natural fluctuations of emissions and the biotic and abiotic factors underlying such variations is essential. In this work, CH4 emission from beach-cast seagrass from the High-Adriatic coast was analysed. Biochemical methane potential (BMP) tests were used to evaluate CH4 generation at different temperatures (30 °C and 35 °C) and salinity levels (from 0‰ to 35‰), consistent with the typical observed environmental conditions. The changes in the microorganism community composition were investigated by means of amplicon metagenomics sequencing. The results underlined a specific CH4 emission in the range of 0.90–1.37 NmL CH4/g Volatile Solids (VS) d at 35 °C and 0.36–0.50 NmL CH4/g VS d at 30 °C. The most intense methane generation was observed at intermediate salinity levels of 18‰ at 35 °C and 9‰ at 30 °C. The total seasonal emission from the investigated beach-cast seagrass was estimated as 0.1399 mmol CH4/m2g. The microbial community analysis highlighted that Rhodobacteraceae was the most abundant family, coherently with its abundance in the marine environment. Low salinity (0–9‰) samples showed a prevalence of carbohydrate–degrading Ruminococcaceae, while the carbohydrate-fermenting Petrotogaceae were more abundant in high salinity (18–35‰) samples. The total lack of an important functional class was not noticed in any salinity level, except for sulphate-reducing bacteria, which were virtually absent when salinity was 0‰. The present study allows a better understanding of the environmental conditions resulting in a higher methanogenic potential and an enhanced comprehension of the bacterial communities associated to this process. The obtained information can be of help for designing efficient systems for producing methane from seagrass wrack, as well as for selecting the most appropriate managing route among the currently available technologies (such as on-site environmental preservation, composting, anaerobic digestion)
Respirometry tests in wastewater treatment: Why and how? A critical review
Full text linkRespirometry tests are a widely employed method in the wastewater treatment field to characterize wastewater streams, assess toxic/inhibitory effects to the biomass, calibrate mathematical models. Respirometry can allow to fractionation the chemical oxygen demand (COD) in biodegradable and inert fractions, but also provide information related to biomass kinetics and stoichiometry through standardized laboratory techniques. Considering the increasing number of emerging contaminants detected in wastewater effluents, such as pharmaceuticals, personal care products and pesticides, respirometry can be a useful tool to promptly assess any toxic or inhibitory effect in wastewater treatment plant (WWTP) operations. Beside conventional activated sludge, in recent years respirometric methods have been applied to innovative fields, such as moving-bed bio-reactors (MBBRs), fungi and microalgae, exploiting natural remediation methods. In particular, respirometry application to microalgae, through the so-called photo-respirometry, has been investigated in the latest years in the treatment of high-loaded streams, allowing resource recovery in biomass form. In this work, respirometric methods are first introduced from a theoretical basis and then critically discussed by considering the experimental apparatus, the available characterization protocols and the fields of application; the most recent literature findings on respirometry are coupled with authors' experience in the field. A comparison between physicochemical methods and respirometry is made. The future research needed on the topic is finally outlined, including the coupling of respirometry with microbial community analysis, potentially leading to an enhanced process understanding, an extended respirometry utilization to get specific kinetic and stoichiometric parameters for modelling purposes, and a wider respirometry application as a diagnosis tool in WWTP operations
Techno-economic feasibility of anaerobic digestion of cheese whey in small Italian dairies and effect of ultrasound pre-treatment on methane yield
No full textIn Friuli-Venezia Giulia plain (North-East of Italy), a significant number of small diaries is present; this study was aimed at evaluating technical and economic feasibility of diffused anaerobic digestion implementation at dairy level. Different kinds of cheese whey were characterized, and biochemical methane potential tests were executed. Good methane yields (up to 437.3 NmL CH4/g VSadded) were obtained, applying an inoculum-to-substrate ratio of 6. Ultrasound pre-treatment was investigated to evaluate an eventual increase in methane production and kinetics, varying applied ultrasonic energy: significant increases in methane yield (maximum +16.0%) and CH4 production kinetics (up to +46% increase after 3 days) were obtained at low ultrasonic energy of 251.4-693.7 Wh/kg VS, while at higher ultrasonic energy of 502.8-1387.5 Wh/kg VS no significant effect was visible. Energy consumption in selected dairies was analysed, to underline the impact of anaerobic digestion implementation on electric and thermal energy need, and it was concluded that through cheese whey anaerobic digestion it is possible to cover most of the dairies energy demand. Specific electric and thermal energy consumption were evaluated to be respectively in the range of 0.009-0.133 kWh/kg milk and 0.247-0.557 MJ/kg milk, while specific energy costs were calculated as 0.0079-0.0308 €/kg milk. For each analysed plant, digester volume to install and organic loading rate were hypothesized
Preliminary evaluation of potential methane production from anaerobic digestion of beach-cast seagrass wrack: the case study of high-Adriatic coast
No full textSeagrass meadows are important productive ecosystems; during the Summer period in touristic beaches, such as those located in the high Adriatic coast, seagrasses are removed from the shoreline and disposed in landfill. This study investigated anaerobic digestion potential of beach-cast seagrass wrack, considering the physicochemical characteristics of the substrate and analysing heavy metal presence in the digestate, with the aim of transporting the material to local wastewater treatment plants to increase biogas yield from excess sludge anaerobic digestion. The methane production obtained from seagrass wrack was compared with three theoretical models. Seagrass wrack had a good methane potential of 103.1-262.3 NmL CH4/g Volatile Solids (VS), depending on substrate humidity and applied inoculum-to-substrate ratio. Predictive models, based on elemental composition and proximate analysis, successfully estimated methane yields; heavy metal concentration in digestate was low, boosting for digestate agricultural reuse. A simplified energy analysis revealed that transport to local wastewater treatment plants and use in anaerobic digestion process would provide up to 245,000 Nm3/y of methane, with an estimated economic income of 33,500-193,300 €/y, considering local seagrass production (1,465-8,454 t/y). Actual yearly costs sustained by beach management company for landfill disposal was about 117,200-676,320 €/y. Seagrass reuse in local digesters would compensate for the lack of excess sludge encountered during the cold season, allowing the digester to operate more continuously, increasing biogas production and reducing plant energy need
Techno-economic analysis of anaerobic digestion implementation in small Italian breweries and evaluation of biochar and granular activated carbon addition effect on methane yield
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