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Sökning: WFRF:(Björnsson Lovisa)

  • Resultat 21-30 av 90
  • Föregående 12[3]4567...9Nästa
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21.
  • Björnsson, Lovisa, et al. (författare)
  • Evaluation of parameters for monitoring an anaerobic co-digestion process
  • 2000
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer. - 1432-0614. ; 54:6, s. 844-849
  • Tidskriftsartikel (refereegranskat)abstract
    • The system investigated in this study is an anaerobic digester at a municipal wastewater treatment plant operating on sludge from the wastewater treatment, co-digested with carbohydrate-rich food-processing waste. The digester is run below maximum capacity to prevent overload. Process monitoring at present is not extensive, even for the measurement of on-line gas production rate and off-line pH. Much could be gained if a better program for monitoring and control was developed, so that the full capacity of the system could be utilised without the risk of overload. The only limit presently set for correct process operation is that the pH should be above 6.8. In the present investigation, the pH was compared with alkalinity, gas production rate, gas composition and the concentration of volatile fatty acids (VFA). Changes in organic load were monitored in the full-scale anaerobic digester and in laboratory-scale models of the plant. Gas-phase parameters showed a slow response to changes in load. The VFA concentrations were superior for indicating overload of the microbial system, but alkalinity and pH also proved to be good monitoring parameters. The possibility of using pH as a process indicator is, however, strongly dependent on the buffering capacity. In this study, a minor change in the amount of carbohydrates in the substrate had drastic effects on the buffering effect of the system.
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22.
  • Björnsson, Lovisa, et al. (författare)
  • Filamentous Chloroflexi are abundant in wastewater treatment processes with biological nutrient removal
  • 2002
  • Ingår i: Microbiology. - : MAIK Nauka/Interperiodica. - 1465-2080. ; 148:8, s. 2309-2318
  • Tidskriftsartikel (refereegranskat)abstract
    • Most filamentous bacteria in biological nutrient removal (BNR) processes have not been identified beyond their morphotype and simple staining reactions. Furthermore, the majority of sludge filaments observed under the microscope do not hybridize to commonly used phylogenetic probes for well characterized bacterial phyla such as the Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. Specific 16S rRNA-targeted oligonucleotide probes were designed for the phylum Chloroflexi (green non-sulfur bacteria) and optimized for use in fluorescence in situ hybridization. Chloroflexi have been implicated in BNR systems by phylogenetic identification of filamentous bacteria isolated by micromanipulation from sludge and culture-independent molecular phylogenetic surveys. The predominant morphotype responding to the probes was filamentous and these filaments were generally abundant in 10 Australian full-scale and two laboratory-scale BNR samples examined. Filamentous bacteria responding to a subdivision 1 Chloroflexi probe were rare in the samples, whereas subdivision 3 Chloroflexi filaments were very common in some sludges. This is in direct contrast to results obtained from molecular phylogenetic surveys of BNR systems where most sludge 16S rDNA clones belong to subdivision 1 and only a few to subdivision 3. It is suggested that filamentous bacteria belonging to the Chloroflexi phylum account for a large fraction of phylogenetically uncharacterized filaments in BNR systems and are likely to be abundant in such systems on a global scale.
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24.
  • Björnsson, Lovisa, et al. (författare)
  • Förbehandling av lignocellulosarika råvaror vid biogasproduktion - Nyckelaspekter vid jämförande utvärdering
  • 2014
  • Rapport (övrigt vetenskapligt)abstract
    • I biogassektorn finns ett ökande behov av och en ökande konkurrens om råvaror, och intresset för användning av odlingsrester, vall, mellangrödor mm som biogasråvara ökar. Gemensamt för dessa råvaror är att de är fiberrika, dvs. har ett högt innehåll av lignocellulosa, vilket gör att det är osannolikt att de skulle användas för biogasproduktion utan förbehandling. Ett antal förbehandlingstekniker har introducerats på marknaden under senare år, och både företagsdrivna projekt och forskningsprojekt kring utvärdering av en eller flera förbehandlingstekniker pågår. Utvärderingarna läggs dock upp med olika utgångspunkter och metoder så att utkomster från olika projekt blir omöjliga att jämföra. Att utreda frågan om hur man utvärderar och jämför olika förbehandlingsmetoder ur teknik-, ekonomi-, energi- och miljöperspektiv är därför angeläget. Syftet med denna förstudie är att peka ut nyckelaspekter som är viktiga för att möjliggöra jämförande utvärdering av olika förbehandlingsmetoder samt att inspirera aktörer till att vilja medverka till att ta ett samlat grepp i frågan. Ett förslag till upplägg för vidare forskning, utveckling och demonstration presenteras. Arbetet med förstudien har finansierats genom Energimyndigheten.
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25.
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26.
  • Björnsson, Lovisa, et al. (författare)
  • Grass biomass as biofuel feedstock –sustainable or not?
  • Ingår i: European Biomass Conference and Exhibition Proceedings, 25thEUBCE, June 2017. - : ETA-Florence Renewable Energies. - 2282-5819. - 9788889407172 ; 2017, s. 39-40
  • Konferensbidrag (refereegranskat)abstract
    • Low carbon input due to increasing specialization, intensification and reduced use of bio-fertilizer, leads to soil organic carbon (SOC) decreases in arable land. This is an emerging problem in Europe in general, where 45% of the EU soils have low and declining SOC content. SOC losses from agricultural soils influence soil fertility, putting food security at risk, and contributes to greenhouse gas (GHG) emissions. An agricultural practice rendering loss of SOC is thus not sustainable in the long term, and measures must be taken to reverse this trend. However, existing policies for agriculture and biofuels address these issues in isolation, SOC impact is not considered when sustainability criteria for biofuels are defined in the EU renewable energy directive (RED). The aim of this study was to illustrate the relevance of SOC impact on integrated production of food and grass as energy crop for biofuel production. This diversification of current cereal dominated crop rotations proved an efficient tool to reverse SOC losses, simultaneously producing a grass-based biofuel with low climate impact. Since SOC-related aspects are excluded in EU RED, the GHG reduction calculated according to the directive does, however, not meet the 60% GHG reduction demand. This narrow perspective causes potentially interesting double benefits to be missed.
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30.
  • Björnsson, Lovisa (författare)
  • Intensification of the biogas process by improved process monitoring and biomass retention
  • 2000
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The utilisation of energy in the form of biogas is one of the environmentally sound alternatives available using renewable energy sources. Biogas is formed by anaerobic degradation of organic material, the main consistuent being energy-rich methane. There is a large unused potential of organic waste that is suitable for biogas production and the anaerobic digestion process has the potential of becoming an important waste treatment and bioenergy generating method in the future. Laws, government grants, taxes and an increasing environmental concern are presently directing developments in a favourable direction for the increased use of the biogas process, but the implementation of anaerobic digestion technology is not straightforward and there is a need for further efforts to develop reliable, economically feasible technology. Anaerobic degradation is performed by a well-organised community of several microbial populations, and is a complex process. Some of the microbial groups involved are slow-growing and sensitive to changes in operating conditions. This can cause instability during both the start-up and operation of the anaerobic process. To make the biogas process more attractive from a commercial point of view, and to facilitate increased integration into our energy supply systems, these instability problems must be overcome in an economically viable way. The purpose of the present work was to investigate different methods of improving the performance and efficiency of the anaerobic digestion process. Based on the knowledge concerning microbial and physical events in the anaerobic digestion process, two main strategies were applied; biomass retention and improved process monitoring. Support materials were utilised to facilitate the retention of slow-growing organisms in biofilms, thereby stabilising the process. It was shown that the protected environment of a biofilm in combination with a long adaptation period made the treatment of toxic wastewater possible. A support material was also successfully used when treating waste containing a high concentration of insoluble particles. No clogging problems occurred, and the retention of important bacteria resulted in a change in metabolic flow and increased process stability. In a two-phase process, a protected environment can be created for the sensitive methanogens. A biosensor that could be used for monitoring of the flow of organic compounds reaching the methanogens was developed. The sensor was able to measure the biochemical oxygen demand (BOD) in a few minutes, making it suitable for on-line monitoring. More efficient operation can be achieved by improving process monitoring, which allows waste treatment at a higher rate. Traditional off-line monitoring methods used in anaerobic digestion were investigated; the results indicating that the present monitoring strategy is not adequate if the process is to be operated at a higher rate. The very rapid response to overload indicates that on-line monitoring is necessary to make suitable process control possible. A new method for utilising a semiconductor sensor for the monitoring of dissolved hydrogen on-line was described. The method was evaluated together with other traditional and new monitoring methods, and proved to be a useful tool in on-line anaerobic digester process monitoring.
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  • Resultat 21-30 av 90
  • Föregående 12[3]4567...9Nästa
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