Contribution of biofouling to permeation flux decline and membrane resistance changes during whey ultrafiltration

This study aimed to quantify the effects of biofouling on the performance of an ultrafiltration system during 24-h recirculation of whey solutions at 0 and 0.8% (w/v) protein. Biofouling by Streptococcus thermophilus and the intrinsic microflora of the ultrafiltration system was either allowed or inhibited with 10 m m sodium azide. Permeate fluxes were reduced by biofouling after 24 h, as normalised flux values with biofouling were 29.0% lower than without biofouling for 0%-protein whey, and 6.5% lower for 0.8%-protein whey. Furthermore, the membrane hydraulic resistances increased, allowing the measurement of biofouling-specific irreversible and reversible resistance values (Rbio) which accounted for 30.7–44.4% of the total fouling layer resistances. These results provide evidence that biofouling can negatively affect the performance of a single ultrafiltration operation. Consequently, pre-treatment of dairy fluids, biofilm management and optimised cleaning procedures are needed to limit the negative impacts of membrane biofouling.