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Vendredi 01 avril 2016 : Thèse de Arthur GAVEAU

Etude des mécanismes de transfert de bactéries déformables en filtration membranaire

PhD thesis defense is set to be held on the 1st of april, 2016, at 10:00 in UPS campus (Rangueil) in room number : Amphi. Concorde Bat. U4

- Title of the PhD thesis :

  • "Transfer Mechanisms of Deformable Bacteria During Dead-End MF"

- Members of the Jury :

  • João CRESPO, Pr, Universidade Nova de Lisboa (NOVA) - Portugal
  • Christelle Wisniewski, Pr, Université de Montpellier
  • Christine LAFFORGUE-BALDAS, MdC, INSA de Toulouse
  • Christine ROQUES, Pr, Université de Toulouse Etienne DAGUE, LAAS, Toulouse
  • Olivier Lorain, Responsable R&D, Polymem SA, Toulouse
  • Christel CAUSSERAND, Pr, Université de Toulouse (Thesis Supervisor)

- Thesis summary :

  • Membrane filtration is a separation technique commonly used as a method for removing and extracting microorganisms present in a fluid.
    The selectivity mechanism is size exclusion. However, our work has highlighted transfer of microorganisms through the porous membrane structure during filtration operations, even if the size of the living cell in suspension is greater than the average pore size of the membrane, resulting in lowering of the accumulation rate of the microorganisms and thus contamination of the permeate phase.
  • Morphological and nanomechanical characterization of selected bacteria cells used for our work were performed and the properties of the model membrane were analyzed. With this information, the transfer of bacteria dunring the first moments of the dead-end filtration has been evaluated and the role of operating parameters (type of bacteria strains, physicochemical composition of filtered fluid, TMP) has been studied. Thus, our results have clarified the selectivity mechanisms applied to Gram-positive and Gram-negative bacteria strains because of different structural characteristics of the bacterial cell wall (thickness and elasticity of the peptidoglycan layer). Finally, evolution of cells transfer to the permeate phase has also been followed, and the bacterial deposit clogging the membrane was observed. The role of the structured deposit on the variations in flow and transfer has been demonstrated for the three selected bacterial models. Our results have defined critical conditions (physical, chemical and biological) where the transfer of bacterial cells is amplified by deformation during a frontal membrane filtration.

- Key Words :

  • membrane process, selectivity mechanism, drinking water production, sterilizing filter, dead-end microfiltration fouling, bacteria


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