Caractérisation morphologique et physiologique de la biomasse des boues activées par analyse d'images :

Abstract : The biological reactors of wastewater treatment by activated sludge are hosting a complex ecosystem, composed of different types of bacteria (filamentous, non filamentous), protozoa and metazoa. A good balance between the different types of bacteria is essential to achieve good settleability properties for the flocs in the clarifier. The flocs are formed by filamentous bacteria and exopolymers produced by zoogleal bacteria. When filamentous bacteria are in excess, the flocs do not settle correctly (bulking and foaming phenomena). Methods based on image analysis have been used to detect and characterize automatically filamentous bacteria as well as the abundance of exopolymers. Monochrome or colour- images have been obtained by optical microscopy with classical (Gram, Neisser, Soudan Black) and fluorescent staining (BacLight, FISH). The validation of the different procedures was achieved on various full-scale treatment plants in Lorraine. Further experiments were carried out on lab-scale continuous and sequential reactors, in order to observe the effect of substrates, of temperature and starvation on the behavior of filamentous microorganisms. Under continuous or sequential aeration, for the same substrate, different Gram characteristics are observed. The study carried out on extracellular polymers with varying carbon/nitrogen ratios reveals that an excess of carbonaceous substance favors the production of polymers, which are essential for flocculation. The results obtained with the Gram and PHB (presence of lipids) procedures in condition of environmental stress (starvation and temperature) have shown that the populations have experienced structural alterations of their membranes. We have noticed that in periods of aerobic starvation the lipids which were present were used in ambient temperature, whereas in anaerobic conditions the polyphosphates were consumed. In absence or presence oxygen at a temperature of 4°C, it seems easier for filamentous bacteria to store those two metabolites. The BacLight coloration has shown that it was possible to quantify the viability of sludge under aerobic starvation and that filamentous or zoogleal bacteria were affected, as opposed to the microfauna
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Denis Pandolfi. Caractérisation morphologique et physiologique de la biomasse des boues activées par analyse d'images :. Autre. Institut National Polytechnique de Lorraine, 2006. Français. ⟨NNT : 2006INPL002N⟩. ⟨tel-01752507⟩

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