Abstract
In a membrane bioreactor (MBR), the tangential flow along the membrane creates significant shear stresses. The purpose of this research consists in underlining the role of these shear stresses in the granulometric distribution of a biological suspension and in the mechanisms of membrane fouling. The role of the different classes of organic particles (settleable, supracolloidal–colloidal, soluble) in membrane fouling is quantified. The laboratory-scale reactor consists of an MBR composed of a pressurizing fermenter associated with a microfiltration module. The activated sludge is recirculated inside the MBR. During this recirculation under different linear velocities, several samples of the suspension are taken off and granulometric analyses and dead-end filtration tests are carried out. The results show that the recirculation induces a modification of the granulometric distribution of the particle size. This change, related to the destructuring of the floc and to the high amount of microflocs, is characterized by a decrease in the settleable fraction and, consequently, by an increase in the non-settleable fraction. Dead-end filtrations of different types of suspension (flocculated and recirculated) show that the shear stresses imposed on the suspension can modify its filterability. Hydraulic resistances obtained for recirculated suspensions are greater than those obtained for flocculated suspensions. Next, the role in the membrane fouling of the three main families of particles (settleable, supracolloidal–colloidal and soluble) is quantified by cross-flow filtrations during MBR operations. The results reveal the significant role of the soluble fraction on membrane permeability: in our operating conditions, half of the total resistance could be due to the soluble compounds. It seems that these different soluble products and their interaction with the membrane material play a major role in the fouling mechanism.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call