ULTRAFILTRATION OF BENTONITE SUSPENSIONS WITH HOLLOW FIBER MEMBRANES

This work gives information for the design and the choice of operating conditions for the production of potable water from surface water by ultrafiltration. Filtration of bentonite suspensions is performed at low crossflow velocity, and the amount of particles deposited on the membrane can be measured as a function of pressure, concentration and velocity. This amount is compared with the amount that would accumulate in dead-end filtration. The difference observed can be explained by the effect of the axial velocity at the scale of a particle. Under our operating conditions, the growth of the hydrodynamic layer from the entrance to the outlet of the module leads to an axial distribution in local velocities, which generates a corresponding variation in cake formation. Mass balance at the wall and velocity distribution then explain the influence of time, pressure and concentration on the flux during ultrafiltration of such suspensions.