Abstract:
Concentration polarization is intrinsically associated with the selective character of
membranes and often means flux decline and which causes a subsequent decrease of ultrafiltration
and nanofiltration performance. More important is the fact that it acts as a precursor of membrane
fouling and creates severe fouling problems in the longer times range. The quantification of its
dependence on the operating parameters of cross-flow velocities and transmembrane pressures
makes recourse to the film theory to introduce mass-transfer coefficients that generally are calculated
by dimensionless correlations of the Sherwood number as a function of the Reynolds and Schmidt
numbers. In the present work, the mass-transfer coefficients are obtained through the fitting of
experimental results by the pressure variation method. The ultrafiltration/nanofiltration of the winery
wastewaters from the racking operation is carried out with the membranes ETNA 01PP (Alfa Laval)
and NF 270 (Dow Filmtec) under a wide range of cross-flow velocities and transmembrane pressures
up to 15 bar.
