| 1. |
- Alpkvist, Erik, et al.
(författare)
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Simulation of nitrification of municipal wastewater in moving-bed biofilm process : approach based on a 2D continuum model for growth and detachment
- 2007
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Ingår i: Water Science and Technology. - : Biriwa Education Services. - 0273-1223 .- 1996-9732. ; 55:8-9, s. 247-255
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a complete mathematical model of a Moving Bed biofilm process for waste-water treatment, in particular for the nitrification process. The model is based on a bottom up approach adopting a multidimensional model for the biofilm growth and metabolism and a global mass balance model for the whole reactor. The model shows that oxygen is limiting the amount of biomass involved in the nitrification process. Furthermore, it suggests the existence of an optimal amount biomass for an optimal reactor turnover rate. Studies of two specific new suspended carriers show that the model output is dependable on the geometry of the carrier, and to a satisfactory extent agreeable with measurements.
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| 2. |
- Bengtsson, Simon, et al.
(författare)
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Production of polyhydroxyalkanoates by activated sludge treating a paper mill wastewater
- 2008
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Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 99:3, s. 509-516
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Tidskriftsartikel (refereegranskat)abstract
- Production of polyhydroxyalkanoates (PHAs) in activated sludge treating wastewater represents an economical and environmental promising alternative to pure culture fermentations. A process for production of PHA from a paper mill wastewater was examined at laboratory scale. The three stage process examined consisted of acidogenic fermentation to convert wastewater organic matter to volatile fatty acids (VFAs), an activated sludge system operating under feast/famine conditions to enrich for PHA producing organisms and accumulation of PHA in batch experiments. After fermentation of the wastewater, 74% of the soluble COD was present as VFA (acetate, propionate, butyrate and valerate) and the resulting PHA after batch accumulation consisted of 31-47 mol% hydroxybutyrate and 5369 mol% hydroxyvalerate. The maximum PHA content achieved was 48% of the sludge dry weight and the three stage process exhibited a potential to produce 0.11 kg of PHA per kg of influent COD treated. (c) 2007 Elsevier Ltd. All rights reserved.
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| 3. |
- Holmberg, Anna, et al.
(författare)
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Biofilm formation by Propionibacterium acnes is a characteristic of invasive isolates
- 2009
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Ingår i: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 15:8, s. 787-795
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Tidskriftsartikel (refereegranskat)abstract
- Propionibacterium acnes is a common and probably underestimated cause of delayed joint prosthesis infection. Bacterial biofilm formation is central in the pathogenesis of infections related to foreign material, and P. acnes has been shown to form biofilm both in vitro and in vivo. Here, biofilm formation by 93 P. acnes isolates, either from invasive infections (n = 45) or from the skin of healthy people (n = 48), was analysed. The majority of isolates from deep infections produced biofilm in a microtitre model of biofilm formation, whereas the skin isolates were poor biofilm producers (p <0.001 for a difference). This indicates a role for biofilm formation in P. acnes virulence. The type distribution, as determined by sequencing of recA, was similar among isolates isolated from skin and from deep infections, demonstrating that P. acnes isolates with different genetic backgrounds have pathogenic potential. The biofilm formed on plastic and on bone cement was analysed by scanning electron microscopy (EM) and by transmission EM. The biofilm was seen as a 10-mum-thick layer covering the bacteria and was composed of filamentous as well as more amorphous structures. Interestingly, the presence of human plasma in solution or at the plastic surface inhibits biofilm formation, which could explain why P. acnes primarily infect plasma-poor environments of, for example, joint prostheses and cerebrospinal shunts. This work underlines the importance of biofilm formation in P. acnes pathogenesis, and shows that biofilm formation should be considered in the diagnosis and treatment of invasive P. acnes infections.
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| 4. |
- Masic, Alma, et al.
(författare)
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Determination of the oxygen profile in a nitrifying Moving Bed Biofilm Reactor by microelectrodes and a mathematical model
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we determine the oxygen profile in a biofilm on suspended carriers in two ways: firstly by microelectrode measurements and secondly by a simple mathematical model. The Moving Bed Biofilm Reactor is well-established for wastewater treatment where bacteria grow as a biofilm on the protective surfaces of suspended carriers. The flat shaped BiofilmChipTM P was developed to allow good conditions for transport of substrates into the biofilm. Firstly, the oxygen profile was measured in situ the nitrifying biofilm with a microelectrode and secondly, the profile was simulated with a one-dimensional mathematical model. We refined a classical model by adding a dynamical tank equation, to connect the tank to the biofilm through the boundary conditions. This proved to be an important key in achieving relevant simulations. We also estimated the erosion parameter λ to increase the concordance between the measured and simulated profiles. Promising results have been obtained from our mathematical model. The accordance improved when simulating profiles without the boundary layer. Microelectrode measurements are a valuable tool in design of new suspended carriers.
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