Design and development of a cross-flow membrane rig to compare constant pressure and constant flux operation in ultrafiltration and microfiltration

Poor understanding of the mechanisms of membrane fouling currently limits commercial application of cross-flow microfiltration (MF) technology. A cross-flow membrane rig that can be operated either at constant transmembrane pressure or at constant permeate flux has been designed and developed. The rig was used to study fouling during ultrafiltration (UF) and MF of skim milk. MF membranes fouled severely at high permeate fluxes, but severe fouling could be prevented by careful start-up procedures and by control of the permeate flux. In contrast, there appeared to be no benefit of constant flux UF operation because severe fouling could not be prevented even at very low permeate fluxes.