LGC :
Immersed membrane bioreactor

Introduction to the filtration


The filtration is a separation process. The main tools of this process are a membrane and a pressure difference, which create the flow. This pressure presses the fluid through the porous media (the membrane). We can also control the flow passing trough the membrane. Nevertheless, this passing causes a side effect, the solid particules block off the pores of the membrane : it's the fauling. There are two types of that : the reversible fauling (we can remove it with various cleanup processes) and the irreversible fauling. The necessary pressure to keep a constant flow will aslo increase in time. The below picture shows this phenomenon.


This picture shows us as well the importance of the reversible fauling (it's removed by backflushing time and less quickly by no suction time) and the importance of the irreversible fauling.

You can find more information about the filtration here.



Experimental device

In order to decrease the fauling, a lot of processes have been created. To best understand one of these processes, the bubble injection, the LGC has built a test bed. His devide is illustrated below.


The principle is easy : it's the creation of a bubbly flow. Nevertheless, the phenomenon of the unfauling aren't understood. The explanation could be lied in one of the three possibilities :



This phenomenon is still unexplained. So, the interest of this project rests upon this problem : why the intermittente injection is efficienter?