Aeration mode, shear stress and sludge rheology in a submerged membrane bioreactor: some keys of energy saving
Résumé
It is nowadays well known that membrane bioreactors (MBR) are advantageous processes allowing to guarantee a rejection of treated effluent respecting both reliability and recent sanitary rules of the European Community. However main drawback for these processes remains the fouling of the membrane which reduces the production performances of the bioreactor. Fouling depends on many parameters dealing with physico-chemistry, biology and operating conditions. It depends in particular on the flocculation state of the sludge. Roughly, it can be take as assessment that the more the sludge is flocculated the weaker the fouling becomes.
This work intends to show how a precise characterization of this state is thus of primary importance in order to optimize the choice of the operating
conditions of the bioreactor. In the case of immersed membrane bioreactors, the mixed liquor flocculation can be altered bythe shearing generated by the aeration used to limit the fouling. The goal of our work is thus to study the potential of shearing generated by the system of aeration on the sludge flocculation. Rheological analyses are a possible key of explanation and lead to a process control proposal.
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