Enhancing microfiltration through an inorganic tubular membrane by gas sparging

A novel technique is tested for reducing tubular mineral membrane fouling by injecting gas into a cross-flow stream. The injected gas is thought to form complex hydrodynamic conditions inside the microfiltration module which increase the wall shear stress, preventing the membrane fouling and enhancing the microfiltration mass transfer. The experimental study was carried out with a ferric hydroxide suspension and a biologically treated wastewater, both of them filtered through a tubular inorganic membrane (Carbosep M14). The sparging led to an increase of the permeate flux with a slug flow structure for the two kinds of suspension. New dimensionless quantities of shear stress number and resistance number were developed by generalized dimensional analysis of steady state flux in sparged and unsparged cross-flow filtration. An unique formalism allowed interpretation of the experimental results both in classical diphasic filtration and with gas sparging. The variation in the dimensionless numbers demonstrated the benefit of gas sparging.